Merge branch 'master' into fix-controlcatatol-person

Avalonia.sln

@@ -206,6 +206,8 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Avalonia.FreeDesktop", "src
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Avalonia.Controls.DataGrid.UnitTests", "tests\Avalonia.Controls.DataGrid.UnitTests\Avalonia.Controls.DataGrid.UnitTests.csproj", "{351337F5-D66F-461B-A957-4EF60BDB4BA6}"
 EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Avalonia.Themes.Fluent", "src\Avalonia.Themes.Fluent\Avalonia.Themes.Fluent.csproj", "{C42D2FC1-A531-4ED4-84B9-89AEC7C962FC}"
+EndProject
 Global
 	GlobalSection(SharedMSBuildProjectFiles) = preSolution
 		src\Shared\RenderHelpers\RenderHelpers.projitems*{3c4c0cb4-0c0f-4450-a37b-148c84ff905f}*SharedItemsImports = 13
@@ -1921,6 +1923,30 @@ Global
 		{351337F5-D66F-461B-A957-4EF60BDB4BA6}.Release|iPhone.Build.0 = Release|Any CPU
 		{351337F5-D66F-461B-A957-4EF60BDB4BA6}.Release|iPhoneSimulator.ActiveCfg = Release|Any CPU
 		{351337F5-D66F-461B-A957-4EF60BDB4BA6}.Release|iPhoneSimulator.Build.0 = Release|Any CPU
+		{C42D2FC1-A531-4ED4-84B9-89AEC7C962FC}.Ad-Hoc|Any CPU.ActiveCfg = Debug|Any CPU
+		{C42D2FC1-A531-4ED4-84B9-89AEC7C962FC}.Ad-Hoc|Any CPU.Build.0 = Debug|Any CPU
+		{C42D2FC1-A531-4ED4-84B9-89AEC7C962FC}.Ad-Hoc|iPhone.ActiveCfg = Debug|Any CPU
+		{C42D2FC1-A531-4ED4-84B9-89AEC7C962FC}.Ad-Hoc|iPhone.Build.0 = Debug|Any CPU
+		{C42D2FC1-A531-4ED4-84B9-89AEC7C962FC}.Ad-Hoc|iPhoneSimulator.ActiveCfg = Debug|Any CPU
+		{C42D2FC1-A531-4ED4-84B9-89AEC7C962FC}.Ad-Hoc|iPhoneSimulator.Build.0 = Debug|Any CPU
+		{C42D2FC1-A531-4ED4-84B9-89AEC7C962FC}.AppStore|Any CPU.ActiveCfg = Debug|Any CPU
+		{C42D2FC1-A531-4ED4-84B9-89AEC7C962FC}.AppStore|Any CPU.Build.0 = Debug|Any CPU
+		{C42D2FC1-A531-4ED4-84B9-89AEC7C962FC}.AppStore|iPhone.ActiveCfg = Debug|Any CPU
+		{C42D2FC1-A531-4ED4-84B9-89AEC7C962FC}.AppStore|iPhone.Build.0 = Debug|Any CPU
+		{C42D2FC1-A531-4ED4-84B9-89AEC7C962FC}.AppStore|iPhoneSimulator.ActiveCfg = Debug|Any CPU
+		{C42D2FC1-A531-4ED4-84B9-89AEC7C962FC}.AppStore|iPhoneSimulator.Build.0 = Debug|Any CPU
+		{C42D2FC1-A531-4ED4-84B9-89AEC7C962FC}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{C42D2FC1-A531-4ED4-84B9-89AEC7C962FC}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{C42D2FC1-A531-4ED4-84B9-89AEC7C962FC}.Debug|iPhone.ActiveCfg = Debug|Any CPU
+		{C42D2FC1-A531-4ED4-84B9-89AEC7C962FC}.Debug|iPhone.Build.0 = Debug|Any CPU
+		{C42D2FC1-A531-4ED4-84B9-89AEC7C962FC}.Debug|iPhoneSimulator.ActiveCfg = Debug|Any CPU
+		{C42D2FC1-A531-4ED4-84B9-89AEC7C962FC}.Debug|iPhoneSimulator.Build.0 = Debug|Any CPU
+		{C42D2FC1-A531-4ED4-84B9-89AEC7C962FC}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{C42D2FC1-A531-4ED4-84B9-89AEC7C962FC}.Release|Any CPU.Build.0 = Release|Any CPU
+		{C42D2FC1-A531-4ED4-84B9-89AEC7C962FC}.Release|iPhone.ActiveCfg = Release|Any CPU
+		{C42D2FC1-A531-4ED4-84B9-89AEC7C962FC}.Release|iPhone.Build.0 = Release|Any CPU
+		{C42D2FC1-A531-4ED4-84B9-89AEC7C962FC}.Release|iPhoneSimulator.ActiveCfg = Release|Any CPU
+		{C42D2FC1-A531-4ED4-84B9-89AEC7C962FC}.Release|iPhoneSimulator.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE

Documentation/build.md

@@ -36,7 +36,7 @@ Avalonia requires [CastXML](https://github.com/CastXML/CastXML) for XML processi
 
 On macOS:
 ```
-brew install castxml
+brew install https://raw.githubusercontent.com/Homebrew/homebrew-core/8a004a91a7fcd3f6620d5b01b6541ff0a640ffba/Formula/castxml.rb
 ```
 
 On Debian based Linux (Debian, Ubuntu, Mint, etc):

build.sh

@@ -67,6 +67,8 @@ else
     fi
 fi
 
+export PATH=$DOTNET_DIRECTORY:$PATH
+
 echo "Microsoft (R) .NET Core SDK version $("$DOTNET_EXE" --version)"
 
 "$DOTNET_EXE" run --project "$BUILD_PROJECT_FILE" -- ${BUILD_ARGUMENTS[@]}

build/CoreLibraries.props

@@ -11,6 +11,7 @@
       <ProjectReference Include="$(MSBuildThisFileDirectory)/../src/Avalonia.Visuals/Avalonia.Visuals.csproj" />
       <ProjectReference Include="$(MSBuildThisFileDirectory)/../src/Avalonia.Styling/Avalonia.Styling.csproj" />
       <ProjectReference Include="$(MSBuildThisFileDirectory)/../src/Avalonia.Themes.Default/Avalonia.Themes.Default.csproj" />
+      <ProjectReference Include="$(MSBuildThisFileDirectory)/../src/Avalonia.Themes.Fluent/Avalonia.Themes.Fluent.csproj" />
       <ProjectReference Include="$(MSBuildThisFileDirectory)/../src/Avalonia.OpenGL/Avalonia.OpenGL.csproj" />
       <ProjectReference Include="$(MSBuildThisFileDirectory)/../src/Avalonia.Dialogs/Avalonia.Dialogs.csproj" />
       <ProjectReference Include="$(MSBuildThisFileDirectory)/../src/Markup/Avalonia.Markup/Avalonia.Markup.csproj" />

native/Avalonia.Native/inc/avalonia-native.h

@@ -22,6 +22,9 @@ struct IAvnGlSurfaceRenderTarget;
 struct IAvnGlSurfaceRenderingSession;
 struct IAvnMenu;
 struct IAvnMenuItem;
+struct IAvnStringArray;
+struct IAvnDndResultCallback;
+struct IAvnGCHandleDeallocatorCallback;
 struct IAvnMenuEvents;
 
 enum SystemDecorations {
@@ -130,6 +133,22 @@ enum AvnInputModifiers
     XButton2MouseButton = 256
 };
 
+enum class AvnDragDropEffects
+{
+    None = 0,
+    Copy = 1,
+    Move = 2,
+    Link = 4,
+};
+
+enum class AvnDragEventType
+{
+    Enter,
+    Over,
+    Leave,
+    Drop
+};
+
 enum AvnWindowState
 {
     Normal,
@@ -188,7 +207,7 @@ enum AvnMenuItemToggleType
 AVNCOM(IAvaloniaNativeFactory, 01) : IUnknown
 {
 public:
-    virtual HRESULT Initialize() = 0;
+    virtual HRESULT Initialize(IAvnGCHandleDeallocatorCallback* deallocator) = 0;
     virtual IAvnMacOptions* GetMacOptions() = 0;
     virtual HRESULT CreateWindow(IAvnWindowEvents* cb, IAvnGlContext* gl, IAvnWindow** ppv) = 0;
     virtual HRESULT CreatePopup (IAvnWindowEvents* cb, IAvnGlContext* gl, IAvnPopup** ppv) = 0;
@@ -196,6 +215,7 @@ public:
     virtual HRESULT CreateSystemDialogs (IAvnSystemDialogs** ppv) = 0;
     virtual HRESULT CreateScreens (IAvnScreens** ppv) = 0;
     virtual HRESULT CreateClipboard(IAvnClipboard** ppv) = 0;
+    virtual HRESULT CreateDndClipboard(IAvnClipboard** ppv) = 0;
     virtual HRESULT CreateCursorFactory(IAvnCursorFactory** ppv) = 0;
     virtual HRESULT ObtainGlDisplay(IAvnGlDisplay** ppv) = 0;
     virtual HRESULT SetAppMenu(IAvnMenu* menu) = 0;
@@ -236,6 +256,9 @@ AVNCOM(IAvnWindowBase, 02) : IUnknown
     virtual HRESULT ObtainNSWindowHandleRetained(void** retOut) = 0;
     virtual HRESULT ObtainNSViewHandle(void** retOut) = 0;
     virtual HRESULT ObtainNSViewHandleRetained(void** retOut) = 0;
+    virtual HRESULT BeginDragAndDropOperation(AvnDragDropEffects effects, AvnPoint point,
+                                              IAvnClipboard* clipboard, IAvnDndResultCallback* cb, void* sourceHandle) = 0;
+    virtual HRESULT SetBlurEnabled (bool enable) = 0;
 };
 
 AVNCOM(IAvnPopup, 03) : virtual IAvnWindowBase
@@ -245,7 +268,8 @@ AVNCOM(IAvnPopup, 03) : virtual IAvnWindowBase
 
 AVNCOM(IAvnWindow, 04) : virtual IAvnWindowBase
 {
-    virtual HRESULT ShowDialog (IAvnWindow* parent) = 0;
+    virtual HRESULT SetEnabled (bool enable) = 0;
+    virtual HRESULT SetParent (IAvnWindow* parent) = 0;
     virtual HRESULT SetCanResize(bool value) = 0;
     virtual HRESULT SetDecorations(SystemDecorations value) = 0;
     virtual HRESULT SetTitle (void* utf8Title) = 0;
@@ -271,6 +295,9 @@ AVNCOM(IAvnWindowBaseEvents, 05) : IUnknown
     virtual bool RawTextInputEvent (unsigned int timeStamp, const char* text) = 0;
     virtual void ScalingChanged(double scaling) = 0;
     virtual void RunRenderPriorityJobs() = 0;
+    virtual AvnDragDropEffects DragEvent(AvnDragEventType type, AvnPoint position,
+                                         AvnInputModifiers modifiers, AvnDragDropEffects effects,
+                                         IAvnClipboard* clipboard, void* dataObjectHandle) = 0;
 };
 
 
@@ -284,6 +311,8 @@ AVNCOM(IAvnWindowEvents, 06) : IAvnWindowBaseEvents
     virtual bool Closing () = 0;
     
     virtual void WindowStateChanged (AvnWindowState state) = 0;
+    
+    virtual void GotInputWhenDisabled () = 0;
 };
 
 AVNCOM(IAvnMacOptions, 07) : IUnknown
@@ -354,8 +383,13 @@ AVNCOM(IAvnScreens, 0e) : IUnknown
 
 AVNCOM(IAvnClipboard, 0f) : IUnknown
 {
-    virtual HRESULT GetText (IAvnString**ppv) = 0;
+    virtual HRESULT GetText (char* type, IAvnString**ppv) = 0;
-    virtual HRESULT SetText (void* utf8Text) = 0;
+    virtual HRESULT SetText (char* type, void* utf8Text) = 0;
+    virtual HRESULT ObtainFormats(IAvnStringArray**ppv) = 0;
+    virtual HRESULT GetStrings(char* type, IAvnStringArray**ppv) = 0;
+    virtual HRESULT SetBytes(char* type, void* utf8Text, int len) = 0;
+    virtual HRESULT GetBytes(char* type, IAvnString**ppv) = 0;
+    
     virtual HRESULT Clear() = 0;
 };
 
@@ -428,4 +462,20 @@ AVNCOM(IAvnMenuEvents, 1A) : IUnknown
     virtual void NeedsUpdate () = 0;
 };
 
+AVNCOM(IAvnStringArray, 20) : IUnknown
+{
+    virtual unsigned int GetCount() = 0;
+    virtual HRESULT Get(unsigned int index, IAvnString**ppv) = 0;
+};
+
+AVNCOM(IAvnDndResultCallback, 21) : IUnknown
+{
+    virtual void OnDragAndDropComplete(AvnDragDropEffects effecct) = 0;
+};
+
+AVNCOM(IAvnGCHandleDeallocatorCallback, 22) : IUnknown
+{
+    virtual void FreeGCHandle(void* handle) = 0;
+};
+
 extern "C" IAvaloniaNativeFactory* CreateAvaloniaNative();

native/Avalonia.Native/src/OSX/Avalonia.Native.OSX.xcodeproj/project.pbxproj

@@ -12,6 +12,7 @@
 		1A3E5EAA23E9F26C00EDE661 /* IOSurface.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 1A3E5EA923E9F26C00EDE661 /* IOSurface.framework */; };
 		1A3E5EAE23E9FB1300EDE661 /* cgl.mm in Sources */ = {isa = PBXBuildFile; fileRef = 1A3E5EAD23E9FB1300EDE661 /* cgl.mm */; };
 		1A3E5EB023E9FE8300EDE661 /* QuartzCore.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 1A3E5EAF23E9FE8300EDE661 /* QuartzCore.framework */; };
+		1A465D10246AB61600C5858B /* dnd.mm in Sources */ = {isa = PBXBuildFile; fileRef = 1A465D0F246AB61600C5858B /* dnd.mm */; };
 		37155CE4233C00EB0034DCE9 /* menu.h in Headers */ = {isa = PBXBuildFile; fileRef = 37155CE3233C00EB0034DCE9 /* menu.h */; };
 		37A517B32159597E00FBA241 /* Screens.mm in Sources */ = {isa = PBXBuildFile; fileRef = 37A517B22159597E00FBA241 /* Screens.mm */; };
 		37C09D8821580FE4006A6758 /* SystemDialogs.mm in Sources */ = {isa = PBXBuildFile; fileRef = 37C09D8721580FE4006A6758 /* SystemDialogs.mm */; };
@@ -33,6 +34,7 @@
 		1A3E5EA923E9F26C00EDE661 /* IOSurface.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = IOSurface.framework; path = System/Library/Frameworks/IOSurface.framework; sourceTree = SDKROOT; };
 		1A3E5EAD23E9FB1300EDE661 /* cgl.mm */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.objcpp; path = cgl.mm; sourceTree = "<group>"; };
 		1A3E5EAF23E9FE8300EDE661 /* QuartzCore.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = QuartzCore.framework; path = System/Library/Frameworks/QuartzCore.framework; sourceTree = SDKROOT; };
+		1A465D0F246AB61600C5858B /* dnd.mm */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.objcpp; path = dnd.mm; sourceTree = "<group>"; };
 		37155CE3233C00EB0034DCE9 /* menu.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = menu.h; sourceTree = "<group>"; };
 		379860FE214DA0C000CD0246 /* KeyTransform.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = KeyTransform.h; sourceTree = "<group>"; };
 		37A4E71A2178846A00EACBCD /* headers */ = {isa = PBXFileReference; lastKnownFileType = folder; name = headers; path = ../../inc; sourceTree = "<group>"; };
@@ -92,6 +94,7 @@
 				5BF943652167AD1D009CAE35 /* cursor.h */,
 				5B21A981216530F500CEE36E /* cursor.mm */,
 				5B8BD94E215BFEA6005ED2A7 /* clipboard.mm */,
+				1A465D0F246AB61600C5858B /* dnd.mm */,
 				AB8F7D6A21482D7F0057DBA5 /* platformthreading.mm */,
 				AB661C212148288600291242 /* common.h */,
 				379860FE214DA0C000CD0246 /* KeyTransform.h */,
@@ -196,6 +199,7 @@
 				37E2330F21583241000CB7E2 /* KeyTransform.mm in Sources */,
 				520624B322973F4100C4DCEF /* menu.mm in Sources */,
 				37A517B32159597E00FBA241 /* Screens.mm in Sources */,
+				1A465D10246AB61600C5858B /* dnd.mm in Sources */,
 				AB00E4F72147CA920032A60A /* main.mm in Sources */,
 				37C09D8821580FE4006A6758 /* SystemDialogs.mm in Sources */,
 				AB661C202148286E00291242 /* window.mm in Sources */,

native/Avalonia.Native/src/OSX/AvnString.h

@@ -10,5 +10,7 @@
 #define AvnString_h
 
 extern IAvnString* CreateAvnString(NSString* string);
-
+extern IAvnStringArray* CreateAvnStringArray(NSArray<NSString*>* array);
+extern IAvnStringArray* CreateAvnStringArray(NSString* string);
+extern IAvnString* CreateByteArray(void* data, int len);
 #endif /* AvnString_h */

native/Avalonia.Native/src/OSX/AvnString.mm

@@ -7,6 +7,7 @@
 //
 
 #include "common.h"
+#include <vector>
 
 class AvnStringImpl : public virtual ComSingleObject<IAvnString, &IID_IAvnString>
 {
@@ -28,6 +29,13 @@ public:
         memcpy((void*)_cstring, (void*)cstring, _length);
     }
     
+    AvnStringImpl(void*ptr, int len)
+    {
+        _length = len;
+        _cstring = (const char*)malloc(_length);
+        memcpy((void*)_cstring, ptr, len);
+    }
+    
     virtual ~AvnStringImpl()
     {
         free((void*)_cstring);
@@ -61,7 +69,60 @@ public:
     }
 };
 
+class AvnStringArrayImpl : public virtual ComSingleObject<IAvnStringArray, &IID_IAvnStringArray>
+{
+private:
+    std::vector<ComPtr<IAvnString>> _list;
+public:
+    FORWARD_IUNKNOWN()
+    AvnStringArrayImpl(NSArray<NSString*>* array)
+    {
+        for(int c = 0; c < [array count]; c++)
+        {
+            ComPtr<IAvnString> s;
+            *s.getPPV() = new AvnStringImpl([array objectAtIndex:c]);
+            _list.push_back(s);
+        }
+    }
+    
+    AvnStringArrayImpl(NSString* string)
+    {
+        ComPtr<IAvnString> s;
+        *s.getPPV() = new AvnStringImpl(string);
+        _list.push_back(s);
+    }
+    
+    virtual unsigned int GetCount() override
+    {
+        return (unsigned int)_list.size();
+    }
+    
+    virtual HRESULT Get(unsigned int index, IAvnString**ppv) override
+    {
+        if(_list.size() <= index)
+            return E_INVALIDARG;
+        *ppv = _list[index].getRetainedReference();
+        return S_OK;
+    }
+};
+
 IAvnString* CreateAvnString(NSString* string)
 {
     return new AvnStringImpl(string);
 }
+
+
+IAvnStringArray* CreateAvnStringArray(NSArray<NSString*> * array)
+{
+    return new AvnStringArrayImpl(array);
+}
+
+IAvnStringArray* CreateAvnStringArray(NSString* string)
+{
+    return new AvnStringArrayImpl(string);
+}
+
+IAvnString* CreateByteArray(void* data, int len)
+{
+    return new AvnStringImpl(data, len);
+}

native/Avalonia.Native/src/OSX/clipboard.mm

@@ -3,16 +3,27 @@
 
 class Clipboard : public ComSingleObject<IAvnClipboard, &IID_IAvnClipboard>
 {
+private:
+    NSPasteboard* _pb;
+    NSPasteboardItem* _item;
 public:
     FORWARD_IUNKNOWN()
     
-    Clipboard()
+    Clipboard(NSPasteboard* pasteboard, NSPasteboardItem* item)
     {
-        NSPasteboard *pasteBoard = [NSPasteboard generalPasteboard];
+        if(pasteboard == nil && item == nil)
-        [pasteBoard stringForType:NSPasteboardTypeString];
+            pasteboard = [NSPasteboard generalPasteboard];
+
+        _pb = pasteboard;
+        _item = item;
     }
     
-    virtual HRESULT GetText (IAvnString**ppv) override
+    NSPasteboardItem* TryGetItem()
+    {
+        return _item;
+    }
+   
+    virtual HRESULT GetText (char* type, IAvnString**ppv) override
     {
         @autoreleasepool
         {
@@ -20,39 +31,124 @@ public:
             {
                 return E_POINTER;
             }
+            NSString* typeString = [NSString stringWithUTF8String:(const char*)type];
+            NSString* string = _item == nil ? [_pb stringForType:typeString] : [_item stringForType:typeString];
             
-            *ppv = CreateAvnString([[NSPasteboard generalPasteboard] stringForType:NSPasteboardTypeString]);
+            *ppv = CreateAvnString(string);
             
             return S_OK;
         }
     }
     
-    virtual HRESULT SetText (void* utf8String) override
+    virtual HRESULT GetStrings(char* type, IAvnStringArray**ppv) override
     {
         @autoreleasepool
         {
-            NSPasteboard *pasteBoard = [NSPasteboard generalPasteboard];
+            *ppv= nil;
-            [pasteBoard clearContents];
+            NSString* typeString = [NSString stringWithUTF8String:(const char*)type];
-            [pasteBoard setString:[NSString stringWithUTF8String:(const char*)utf8String] forType:NSPasteboardTypeString];
+            NSObject* data = _item == nil ? [_pb propertyListForType: typeString] : [_item propertyListForType: typeString];
+            if(data == nil)
+                return S_OK;
+            
+            if([data isKindOfClass: [NSString class]])
+            {
+                *ppv = CreateAvnStringArray((NSString*) data);
+                return S_OK;
+            }
+            
+            NSArray* arr = (NSArray*)data;
+            
+            for(int c = 0; c < [arr count]; c++)
+                if(![[arr objectAtIndex:c] isKindOfClass:[NSString class]])
+                    return E_INVALIDARG;
+            
+            *ppv = CreateAvnStringArray(arr);
+            return S_OK;
+        }
+    }
+    
+    virtual HRESULT SetText (char* type, void* utf8String) override
+    {
+        Clear();
+        @autoreleasepool
+        {
+            auto string = [NSString stringWithUTF8String:(const char*)utf8String];
+            auto typeString = [NSString stringWithUTF8String:(const char*)type];
+            if(_item == nil)
+                [_pb setString: string forType: typeString];
+            else
+                [_item setString: string forType:typeString];
         }
         
         return S_OK;
     }
+    
+    virtual HRESULT SetBytes(char* type, void* bytes, int len) override
+    {
+        auto typeString = [NSString stringWithUTF8String:(const char*)type];
+        auto data = [NSData dataWithBytes:bytes length:len];
+        if(_item == nil)
+            [_pb setData:data forType:typeString];
+        else
+            [_item setData:data forType:typeString];
+        return S_OK;
+    }
+       
+    virtual HRESULT GetBytes(char* type, IAvnString**ppv) override
+    {
+        *ppv = nil;
+        auto typeString = [NSString stringWithUTF8String:(const char*)type];
+        NSData*data;
+        @try
+        {
+            if(_item)
+                data = [_item dataForType:typeString];
+            else
+                data = [_pb dataForType:typeString];
+            if(data == nil)
+                return E_FAIL;
+        }
+        @catch(NSException* e)
+        {
+            return E_FAIL;
+        }
+        *ppv = CreateByteArray((void*)data.bytes, (int)data.length);
+        return S_OK;
+    }
+
 
     virtual HRESULT Clear() override
     {
         @autoreleasepool
         {
-            NSPasteboard *pasteBoard = [NSPasteboard generalPasteboard];
+            if(_item != nil)
-            [pasteBoard clearContents];
+                _item = [NSPasteboardItem new];
-            [pasteBoard setString:@"" forType:NSPasteboardTypeString];
+            else
+            {
+                [_pb clearContents];
+                [_pb setString:@"" forType:NSPasteboardTypeString];
+            }
         }
         
         return S_OK;
     }
+    
+    virtual HRESULT ObtainFormats(IAvnStringArray** ppv) override
+    {
+        *ppv = CreateAvnStringArray(_item == nil ? [_pb types] : [_item types]);
+        return S_OK;
+    }
 };
 
-extern IAvnClipboard* CreateClipboard()
+extern IAvnClipboard* CreateClipboard(NSPasteboard* pb, NSPasteboardItem* item)
+{
+    return new Clipboard(pb, item);
+}
+
+extern NSPasteboardItem* TryGetPasteboardItem(IAvnClipboard*cb)
 {
-    return new Clipboard();
+    auto clipboard = dynamic_cast<Clipboard*>(cb);
+    if(clipboard == nil)
+        return nil;
+    return clipboard->TryGetItem();
 }

native/Avalonia.Native/src/OSX/common.h

@@ -8,11 +8,17 @@
 #include <pthread.h>
 
 extern IAvnPlatformThreadingInterface* CreatePlatformThreading();
+extern void FreeAvnGCHandle(void* handle);
 extern IAvnWindow* CreateAvnWindow(IAvnWindowEvents*events, IAvnGlContext* gl);
 extern IAvnPopup* CreateAvnPopup(IAvnWindowEvents*events, IAvnGlContext* gl);
 extern IAvnSystemDialogs* CreateSystemDialogs();
 extern IAvnScreens* CreateScreens();
-extern IAvnClipboard* CreateClipboard();
+extern IAvnClipboard* CreateClipboard(NSPasteboard*, NSPasteboardItem*);
+extern NSPasteboardItem* TryGetPasteboardItem(IAvnClipboard*);
+extern NSObject<NSDraggingSource>* CreateDraggingSource(NSDragOperation op, IAvnDndResultCallback* cb, void* handle);
+extern void* GetAvnDataObjectHandleFromDraggingInfo(NSObject<NSDraggingInfo>* info);
+extern NSString* GetAvnCustomDataType();
+extern AvnDragDropEffects ConvertDragDropEffects(NSDragOperation nsop);
 extern IAvnCursorFactory* CreateCursorFactory();
 extern IAvnGlDisplay* GetGlDisplay();
 extern IAvnMenu* CreateAppMenu(IAvnMenuEvents* events);

native/Avalonia.Native/src/OSX/dnd.mm

@@ -0,0 +1,89 @@
+#include "common.h"
+
+extern AvnDragDropEffects ConvertDragDropEffects(NSDragOperation nsop)
+{
+    int effects = 0;
+    if((nsop & NSDragOperationCopy) != 0)
+        effects |= (int)AvnDragDropEffects::Copy;
+    if((nsop & NSDragOperationMove) != 0)
+        effects |= (int)AvnDragDropEffects::Move;
+    if((nsop & NSDragOperationLink) != 0)
+        effects |= (int)AvnDragDropEffects::Link;
+    return (AvnDragDropEffects)effects;
+};
+
+extern NSString* GetAvnCustomDataType()
+{
+    char buffer[256];
+    sprintf(buffer, "net.avaloniaui.inproc.uti.n%in", getpid());
+    return [NSString stringWithUTF8String:buffer];
+}
+
+@interface AvnDndSource : NSObject<NSDraggingSource>
+
+@end
+
+@implementation AvnDndSource
+{
+    NSDragOperation _operation;
+    ComPtr<IAvnDndResultCallback> _cb;
+    void* _sourceHandle;
+};
+
+- (NSDragOperation)draggingSession:(nonnull NSDraggingSession *)session sourceOperationMaskForDraggingContext:(NSDraggingContext)context
+{
+    return NSDragOperationCopy;
+}
+
+- (AvnDndSource*) initWithOperation: (NSDragOperation)operation
+                        andCallback: (IAvnDndResultCallback*) cb
+                    andSourceHandle: (void*) handle
+{
+    self = [super init];
+    _operation = operation;
+    _cb = cb;
+    _sourceHandle = handle;
+    return self;
+}
+
+- (void)draggingSession:(NSDraggingSession *)session
+           endedAtPoint:(NSPoint)screenPoint
+              operation:(NSDragOperation)operation
+{
+    if(_cb != nil)
+    {
+        auto cb = _cb;
+        _cb = nil;
+        cb->OnDragAndDropComplete(ConvertDragDropEffects(operation));
+    }
+    if(_sourceHandle != nil)
+    {
+        FreeAvnGCHandle(_sourceHandle);
+        _sourceHandle = nil;
+    }
+}
+
+- (void*) gcHandle
+{
+    return _sourceHandle;
+}
+
+@end
+
+extern NSObject<NSDraggingSource>* CreateDraggingSource(NSDragOperation op, IAvnDndResultCallback* cb, void* handle)
+{
+    return [[AvnDndSource alloc] initWithOperation:op andCallback:cb andSourceHandle:handle];
+};
+
+extern void* GetAvnDataObjectHandleFromDraggingInfo(NSObject<NSDraggingInfo>* info)
+{
+    id obj = [info draggingSource];
+    if(obj == nil)
+        return nil;
+    if([obj isKindOfClass: [AvnDndSource class]])
+    {
+        auto src = (AvnDndSource*)obj;
+        return [src gcHandle];
+    }
+    return nil;
+}

native/Avalonia.Native/src/OSX/main.mm

@@ -150,14 +150,15 @@ public:
 }
 @end
 
-
+static ComPtr<IAvnGCHandleDeallocatorCallback> _deallocator;
 class AvaloniaNative : public ComSingleObject<IAvaloniaNativeFactory, &IID_IAvaloniaNativeFactory>
 {
     
 public:
     FORWARD_IUNKNOWN()
-    virtual HRESULT Initialize() override
+    virtual HRESULT Initialize(IAvnGCHandleDeallocatorCallback* deallocator) override
     {
+        _deallocator = deallocator;
         @autoreleasepool{
             [[ThreadingInitializer new] do];
         }
@@ -207,7 +208,13 @@ public:
 
     virtual HRESULT CreateClipboard(IAvnClipboard** ppv) override
     {
-        *ppv = ::CreateClipboard ();
+        *ppv = ::CreateClipboard (nil, nil);
+        return S_OK;
+    }
+    
+    virtual HRESULT CreateDndClipboard(IAvnClipboard** ppv) override
+    {
+        *ppv = ::CreateClipboard (nil, [NSPasteboardItem new]);
         return S_OK;
     }
 
@@ -257,6 +264,12 @@ extern "C" IAvaloniaNativeFactory* CreateAvaloniaNative()
     return new AvaloniaNative();
 };
 
+extern void FreeAvnGCHandle(void* handle)
+{
+    if(_deallocator != nil)
+        _deallocator->FreeGCHandle(handle);
+}
+
 NSSize ToNSSize (AvnSize s)
 {
     NSSize result;

native/Avalonia.Native/src/OSX/window.h

@@ -3,7 +3,10 @@
 
 class WindowBaseImpl;
 
-@interface AvnView : NSView<NSTextInputClient>
+@interface AutoFitContentVisualEffectView : NSVisualEffectView
+@end
+
+@interface AvnView : NSView<NSTextInputClient, NSDraggingDestination>
 -(AvnView* _Nonnull) initWithParent: (WindowBaseImpl* _Nonnull) parent;
 -(NSEvent* _Nonnull) lastMouseDownEvent;
 -(AvnPoint) translateLocalPoint:(AvnPoint)pt;
@@ -19,8 +22,7 @@ class WindowBaseImpl;
 -(void) pollModalSession: (NSModalSession _Nonnull) session;
 -(void) restoreParentWindow;
 -(bool) shouldTryToHandleEvents;
--(bool) isModal;
+-(void) setEnabled: (bool) enable;
--(void) setModal: (bool) isModal;
 -(void) showAppMenuOnly;
 -(void) showWindowMenuWithAppMenu;
 -(void) applyMenu:(NSMenu* _Nullable)menu;

native/Avalonia.Native/src/OSX/window.mm

@@ -20,6 +20,7 @@ public:
         View = NULL;
         Window = NULL;
     }
+    NSVisualEffectView* VisualEffect;
     AvnView* View;
     AvnWindow* Window;
     ComPtr<IAvnWindowBaseEvents> BaseEvents;
@@ -47,6 +48,12 @@ public:
         
         [Window setStyleMask:NSWindowStyleMaskBorderless];
         [Window setBackingType:NSBackingStoreBuffered];
+        
+        VisualEffect = [AutoFitContentVisualEffectView new];
+        [VisualEffect setBlendingMode:NSVisualEffectBlendingModeBehindWindow];
+        [VisualEffect setMaterial:NSVisualEffectMaterialLight];
+        [VisualEffect setAutoresizesSubviews:true];
+        
         [Window setContentView: View];
     }
     
@@ -382,6 +389,62 @@ public:
         *ppv = [renderTarget createSurfaceRenderTarget];
         return *ppv == nil ? E_FAIL : S_OK;
     }
+    
+    virtual HRESULT SetBlurEnabled (bool enable) override
+    {
+        [Window setContentView: enable ? VisualEffect : View];
+        
+        if(enable)
+        {
+            [VisualEffect addSubview:View];
+        }
+        
+        return S_OK;
+    }
+    
+    virtual HRESULT BeginDragAndDropOperation(AvnDragDropEffects effects, AvnPoint point,
+                                              IAvnClipboard* clipboard, IAvnDndResultCallback* cb,
+                                              void* sourceHandle) override
+    {
+        auto item = TryGetPasteboardItem(clipboard);
+        [item setString:@"" forType:GetAvnCustomDataType()];
+        if(item == nil)
+            return E_INVALIDARG;
+        if(View == NULL)
+            return E_FAIL;
+        
+        auto nsevent = [NSApp currentEvent];
+        auto nseventType = [nsevent type];
+        
+        // If current event isn't a mouse one (probably due to malfunctioning user app)
+        // attempt to forge a new one
+        if(!((nseventType >= NSEventTypeLeftMouseDown && nseventType <= NSEventTypeMouseExited)
+           || (nseventType >= NSEventTypeOtherMouseDown && nseventType <= NSEventTypeOtherMouseDragged)))
+        {
+            auto nspoint = [Window convertBaseToScreen: ToNSPoint(point)];
+            CGPoint cgpoint = NSPointToCGPoint(nspoint);
+            auto cgevent = CGEventCreateMouseEvent(NULL, kCGEventLeftMouseDown, cgpoint, kCGMouseButtonLeft);
+            nsevent = [NSEvent eventWithCGEvent: cgevent];
+            CFRelease(cgevent);
+        }
+        
+        auto dragItem = [[NSDraggingItem alloc] initWithPasteboardWriter: item];
+        
+        auto dragItemImage = [NSImage imageNamed:NSImageNameMultipleDocuments];
+        NSRect dragItemRect = {(float)point.X, (float)point.Y, [dragItemImage size].width, [dragItemImage size].height};
+        [dragItem setDraggingFrame: dragItemRect contents: dragItemImage];
+        
+        int op = 0; int ieffects = (int)effects;
+        if((ieffects & (int)AvnDragDropEffects::Copy) != 0)
+            op |= NSDragOperationCopy;
+        if((ieffects & (int)AvnDragDropEffects::Link) != 0)
+            op |= NSDragOperationLink;
+        if((ieffects & (int)AvnDragDropEffects::Move) != 0)
+            op |= NSDragOperationMove;
+        [View beginDraggingSessionWithItems: @[dragItem] event: nsevent
+                                     source: CreateDraggingSource((NSDragOperation) op, cb, sourceHandle)];
+        return S_OK;
+    }
 
 protected:
     virtual NSWindowStyleMask GetStyle()
@@ -453,12 +516,7 @@ private:
     virtual HRESULT Show () override
     {
         @autoreleasepool
-        {
+        {            
-            if([Window parentWindow] != nil)
-                [[Window parentWindow] removeChildWindow:Window];
-            
-            [Window setModal:FALSE];
-            
             WindowBaseImpl::Show();
             
             HideOrShowTrafficLights();
@@ -467,7 +525,16 @@ private:
         }
     }
     
-    virtual HRESULT ShowDialog (IAvnWindow* parent) override
+    virtual HRESULT SetEnabled (bool enable) override
+    {
+        @autoreleasepool
+        {
+            [Window setEnabled:enable];
+            return S_OK;
+        }
+    }
+    
+    virtual HRESULT SetParent (IAvnWindow* parent) override
     {
         @autoreleasepool
         {
@@ -478,12 +545,9 @@ private:
             if(cparent == nullptr)
                 return E_INVALIDARG;
             
-            [Window setModal:TRUE];
-            
             [cparent->Window addChildWindow:Window ordered:NSWindowAbove];
-            WindowBaseImpl::Show();
             
-            HideOrShowTrafficLights();
+            UpdateStyle();
             
             return S_OK;
         }
@@ -839,15 +903,15 @@ protected:
         switch (_decorations)
         {
             case SystemDecorationsNone:
-                s = s | NSWindowStyleMaskFullSizeContentView | NSWindowStyleMaskMiniaturizable;
+                s = s | NSWindowStyleMaskFullSizeContentView;
                 break;
 
             case SystemDecorationsBorderOnly:
-                s = s | NSWindowStyleMaskTitled | NSWindowStyleMaskFullSizeContentView | NSWindowStyleMaskMiniaturizable;
+                s = s | NSWindowStyleMaskTitled | NSWindowStyleMaskFullSizeContentView;
                 break;
 
             case SystemDecorationsFull:
-                s = s | NSWindowStyleMaskTitled | NSWindowStyleMaskClosable | NSWindowStyleMaskMiniaturizable | NSWindowStyleMaskBorderless;
+                s = s | NSWindowStyleMaskTitled | NSWindowStyleMaskClosable | NSWindowStyleMaskBorderless;
                 
                 if(_canResize)
                 {
@@ -856,12 +920,26 @@ protected:
                 break;
         }
 
+        if([Window parentWindow] == nullptr)
+        {
+            s |= NSWindowStyleMaskMiniaturizable;
+        }
         return s;
     }
 };
 
 NSArray* AllLoopModes = [NSArray arrayWithObjects: NSDefaultRunLoopMode, NSEventTrackingRunLoopMode, NSModalPanelRunLoopMode, NSRunLoopCommonModes, NSConnectionReplyMode, nil];
 
+@implementation AutoFitContentVisualEffectView
+-(void)setFrameSize:(NSSize)newSize
+{
+    [super setFrameSize:newSize];
+    if([[self subviews] count] == 0)
+        return;
+    [[self subviews][0] setFrameSize: newSize];
+}
+@end
+
 @implementation AvnView
 {
     ComPtr<WindowBaseImpl> _parent;
@@ -911,7 +989,7 @@ NSArray* AllLoopModes = [NSArray arrayWithObjects: NSDefaultRunLoopMode, NSEvent
     _area = nullptr;
     _lastPixelSize.Height = 100;
     _lastPixelSize.Width = 100;
-
+    [self registerForDraggedTypes: @[@"public.data", GetAvnCustomDataType()]];
     return self;
 }
 
@@ -1037,15 +1115,28 @@ NSArray* AllLoopModes = [NSArray arrayWithObjects: NSDefaultRunLoopMode, NSEvent
 - (bool) ignoreUserInput
 {
     auto parentWindow = objc_cast<AvnWindow>([self window]);
+    
     if(parentWindow == nil || ![parentWindow shouldTryToHandleEvents])
+    {
+        auto window = dynamic_cast<WindowImpl*>(_parent.getRaw());
+        
+        if(window != nullptr)
+        {
+            window->WindowEvents->GotInputWhenDisabled();
+        }
+        
         return TRUE;
+    }
+    
     return FALSE;
 }
 
 - (void)mouseEvent:(NSEvent *)event withType:(AvnRawMouseEventType) type
 {
     if([self ignoreUserInput])
+    {
         return;
+    }
     
     [self becomeFirstResponder];
     auto localPoint = [self convertPoint:[event locationInWindow] toView:self];
@@ -1190,7 +1281,10 @@ NSArray* AllLoopModes = [NSArray arrayWithObjects: NSDefaultRunLoopMode, NSEvent
 - (void) keyboardEvent: (NSEvent *) event withType: (AvnRawKeyEventType)type
 {
     if([self ignoreUserInput])
+    {
         return;
+    }
+    
     auto key = s_KeyMap[[event keyCode]];
     
     auto timestamp = [event timestamp] * 1000;
@@ -1302,6 +1396,68 @@ NSArray* AllLoopModes = [NSArray arrayWithObjects: NSDefaultRunLoopMode, NSEvent
     
     return result;
 }
+
+- (NSDragOperation)triggerAvnDragEvent: (AvnDragEventType) type info: (id <NSDraggingInfo>)info
+{
+    auto localPoint = [self convertPoint:[info draggingLocation] toView:self];
+    auto avnPoint = [self toAvnPoint:localPoint];
+    auto point = [self translateLocalPoint:avnPoint];
+    auto modifiers = [self getModifiers:[[NSApp currentEvent] modifierFlags]];
+    NSDragOperation nsop = [info draggingSourceOperationMask];
+   
+        auto effects = ConvertDragDropEffects(nsop);
+    int reffects = (int)_parent->BaseEvents
+    ->DragEvent(type, point, modifiers, effects,
+                CreateClipboard([info draggingPasteboard], nil),
+                GetAvnDataObjectHandleFromDraggingInfo(info));
+    
+    NSDragOperation ret = 0;
+    
+    // Ensure that the managed part didn't add any new effects
+    reffects = (int)effects & (int)reffects;
+    
+    // OSX requires exactly one operation
+    if((reffects & (int)AvnDragDropEffects::Copy) != 0)
+        ret = NSDragOperationCopy;
+    else if((reffects & (int)AvnDragDropEffects::Move) != 0)
+        ret = NSDragOperationMove;
+    else if((reffects & (int)AvnDragDropEffects::Link) != 0)
+        ret = NSDragOperationLink;
+    if(ret == 0)
+        ret = NSDragOperationNone;
+    return ret;
+}
+
+- (NSDragOperation)draggingEntered:(id <NSDraggingInfo>)sender
+{
+    return [self triggerAvnDragEvent: AvnDragEventType::Enter info:sender];
+}
+
+- (NSDragOperation)draggingUpdated:(id <NSDraggingInfo>)sender
+{
+    return [self triggerAvnDragEvent: AvnDragEventType::Over info:sender];
+}
+
+- (void)draggingExited:(id <NSDraggingInfo>)sender
+{
+    [self triggerAvnDragEvent: AvnDragEventType::Leave info:sender];
+}
+
+- (BOOL)prepareForDragOperation:(id <NSDraggingInfo>)sender
+{
+    return [self triggerAvnDragEvent: AvnDragEventType::Over info:sender] != NSDragOperationNone;
+}
+
+- (BOOL)performDragOperation:(id <NSDraggingInfo>)sender
+{
+    return [self triggerAvnDragEvent: AvnDragEventType::Drop info:sender] != NSDragOperationNone;
+}
+
+- (void)concludeDragOperation:(nullable id <NSDraggingInfo>)sender
+{
+    
+}
+
 @end
 
 
@@ -1310,7 +1466,7 @@ NSArray* AllLoopModes = [NSArray arrayWithObjects: NSDefaultRunLoopMode, NSEvent
     ComPtr<WindowBaseImpl> _parent;
     bool _canBecomeKeyAndMain;
     bool _closed;
-    bool _isModal;
+    bool _isEnabled;
     AvnMenu* _menu;
     double _lastScaling;
 }
@@ -1432,6 +1588,7 @@ NSArray* AllLoopModes = [NSArray arrayWithObjects: NSDefaultRunLoopMode, NSEvent
     _parent = parent;
     [self setDelegate:self];
     _closed = false;
+    _isEnabled = true;
     
     _lastScaling = [self backingScaleFactor];
     [self setOpaque:NO];
@@ -1498,28 +1655,12 @@ NSArray* AllLoopModes = [NSArray arrayWithObjects: NSDefaultRunLoopMode, NSEvent
 
 -(bool)shouldTryToHandleEvents
 {
-    for(NSWindow* uch in [self childWindows])
+    return _isEnabled;
-    {
-        auto ch = objc_cast<AvnWindow>(uch);
-        if(ch == nil)
-            continue;
-        
-        if(![ch isModal])
-            continue;
-        
-        return FALSE;
-    }
-    return TRUE;
-}
-
--(bool) isModal
-{
-    return _isModal;
 }
 
--(void) setModal: (bool) isModal
+-(void) setEnabled:(bool)enable
 {
-    _isModal = isModal;
+    _isEnabled = enable;
 }
 
 -(void)makeKeyWindow

packages/Avalonia/AvaloniaBuildTasks.targets

@@ -2,6 +2,7 @@
   <PropertyGroup>
     <_AvaloniaUseExternalMSBuild>$(AvaloniaUseExternalMSBuild)</_AvaloniaUseExternalMSBuild>
     <_AvaloniaUseExternalMSBuild Condition="'$(_AvaloniaForceInternalMSBuild)' == 'true'">false</_AvaloniaUseExternalMSBuild>
+    <AvaloniaXamlReportImportance Condition="'$(AvaloniaXamlReportImportance)' == ''">low</AvaloniaXamlReportImportance>
   </PropertyGroup>
   
   <UsingTask TaskName="GenerateAvaloniaResourcesTask"
@@ -38,7 +39,8 @@
       Output="$(AvaloniaResourcesTemporaryFilePath)"
       Root="$(MSBuildProjectDirectory)"
       Resources="@(AvaloniaResource)"
-      EmbeddedResources="@(EmbeddedResources)"/>
+      EmbeddedResources="@(EmbeddedResources)"
+      ReportImportance="$(AvaloniaXamlReportImportance)"/>
     <Exec 
       Condition="'$(_AvaloniaUseExternalMSBuild)' == 'true'"
       Command="dotnet msbuild /nodereuse:false $(MSBuildProjectFile) /t:GenerateAvaloniaResources /p:_AvaloniaForceInternalMSBuild=true /p:Configuration=$(Configuration) /p:TargetFramework=$(TargetFramework) /p:BuildProjectReferences=false"/>
@@ -67,6 +69,7 @@
       OriginalCopyPath="$(AvaloniaXamlOriginalCopyFilePath)"
       ProjectDirectory="$(MSBuildProjectDirectory)"
       VerifyIl="$(AvaloniaXamlIlVerifyIl)"
+      ReportImportance="$(AvaloniaXamlReportImportance)"
     />
     <Exec
       Condition="'$(_AvaloniaUseExternalMSBuild)' == 'true'"

readme.md

@@ -1,24 +1,20 @@
-<img src='https://avatars2.githubusercontent.com/u/14075148?s=200&v=4' width='100' />
+[![Gitter](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/AvaloniaUI/Avalonia?utm_campaign=pr-badge&utm_content=badge&utm_medium=badge&utm_source=badge) [![Build Status](https://dev.azure.com/AvaloniaUI/AvaloniaUI/_apis/build/status/AvaloniaUI.Avalonia)](https://dev.azure.com/AvaloniaUI/AvaloniaUI/_build/latest?definitionId=4) [![Backers on Open Collective](https://opencollective.com/Avalonia/backers/badge.svg)](#backers) [![Sponsors on Open Collective](https://opencollective.com/Avalonia/sponsors/badge.svg)](#sponsors) ![License](https://img.shields.io/github/license/avaloniaui/avalonia.svg)
+<br />
+[![NuGet](https://img.shields.io/nuget/v/Avalonia.svg)](https://www.nuget.org/packages/Avalonia) [![downloads](https://img.shields.io/nuget/dt/avalonia)](https://www.nuget.org/packages/Avalonia) [![MyGet](https://img.shields.io/myget/avalonia-ci/vpre/Avalonia.svg?label=myget)](https://www.myget.org/gallery/avalonia-ci) ![Size](https://img.shields.io/github/repo-size/avaloniaui/avalonia.svg) 
 
-# Avalonia
+<img alt="Avalonia" src="https://user-images.githubusercontent.com/6759207/84897744-cab6d800-b0ae-11ea-8214-e5174d71f5c8.png" width="400"/>
 
-| Gitter Chat | Build Status (Win, Linux, OSX) | Open Collective | NuGet | MyGet |
+## 📖 About AvaloniaUI 
-|---|---|---|---|---|
-|  [![Gitter](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/AvaloniaUI/Avalonia?utm_campaign=pr-badge&utm_content=badge&utm_medium=badge&utm_source=badge) | [![Build Status](https://dev.azure.com/AvaloniaUI/AvaloniaUI/_apis/build/status/AvaloniaUI.Avalonia)](https://dev.azure.com/AvaloniaUI/AvaloniaUI/_build/latest?definitionId=4) | [![Backers on Open Collective](https://opencollective.com/Avalonia/backers/badge.svg)](#backers) [![Sponsors on Open Collective](https://opencollective.com/Avalonia/sponsors/badge.svg)](#sponsors) | [![NuGet](https://img.shields.io/nuget/v/Avalonia.svg)](https://www.nuget.org/packages/Avalonia) | [![MyGet](https://img.shields.io/myget/avalonia-ci/vpre/Avalonia.svg?label=myget)](https://www.myget.org/gallery/avalonia-ci) |
 
-## About
+Avalonia is a cross-platform XAML-based UI framework providing a flexible styling system and supporting a wide range of Operating Systems such as Windows via .NET Framework and .NET Core, Linux via Xorg, macOS. Avalonia is ready for **General-Purpose Desktop App Development**. However, there may be some bugs and breaking changes as we continue along into this project's development. 
 
-**Avalonia** is a cross-platform XAML-based UI framework providing a flexible styling system and supporting a wide range of Operating Systems such as Windows (.NET Framework, .NET Core), Linux (via Xorg), macOS.
+<img src="https://user-images.githubusercontent.com/6759207/84751662-7c79da00-afc5-11ea-8780-dda28db70b76.png" width="700" />
 
-**Avalonia** is ready for **General-Purpose Desktop App Development**. However, there may be some bugs and breaking changes as we continue along into this project's development.
+> **Note:** The UI theme you see in the picture above is still work-in-progress and will be available in the upcoming Avalonia 0.10.0 release. However, you can connect to our nightly build feed and install latest pre-release versions of Avalonia NuGet packages, if you are willing to help out with the development and testing. See [Using nightly build feed](https://github.com/AvaloniaUI/Avalonia/wiki/Using-nightly-build-feed) for more info.
 
-To see the status of some of our features, please see our [Roadmap here](https://github.com/AvaloniaUI/Avalonia/issues/2239).
+To see the status of some of our features, please see our [Roadmap](https://github.com/AvaloniaUI/Avalonia/issues/2239). You can also see what [breaking changes](https://github.com/AvaloniaUI/Avalonia/issues/3538) we have planned and what our [past breaking changes](https://github.com/AvaloniaUI/Avalonia/wiki/Breaking-Changes) have been. [Awesome Avalonia](https://github.com/AvaloniaCommunity/awesome-avalonia) is community-curated list of awesome Avalonia UI tools, libraries, projects and resources. Go and see what people are building with Avalonia!
 
-You can also see what [breaking changes](https://github.com/AvaloniaUI/Avalonia/issues/3538) we have planned and what our [past breaking changes](https://github.com/AvaloniaUI/Avalonia/wiki/Breaking-Changes) have been.
+## 🚀 Getting Started
-
-[Awesome Avalonia](https://github.com/AvaloniaCommunity/awesome-avalonia) is community-curated list of awesome Avalonia UI tools, libraries, projects and resources. Go and see what people are building with Avalonia!
-
-## Getting Started
 
 The Avalonia [Visual Studio Extension](https://marketplace.visualstudio.com/items?itemName=AvaloniaTeam.AvaloniaforVisualStudio) contains project and control templates that will help you get started, or you can use the .NET Core CLI. For a starer guide see our [documentation](http://avaloniaui.net/docs/quickstart/create-new-project).
 
@@ -30,6 +26,15 @@ Install-Package Avalonia
 Install-Package Avalonia.Desktop
 ```
 
+## Showcase
+
+Examples of UIs built with Avalonia
+![image](https://user-images.githubusercontent.com/4672627/84707589-5b69a880-af35-11ea-87a6-7ad57a31d314.png)
+
+![image](https://user-images.githubusercontent.com/4672627/84708576-28281900-af37-11ea-8c88-e29dfcfa0558.png)
+
+![image](https://user-images.githubusercontent.com/4672627/84708947-c3b98980-af37-11ea-8c9d-503334615bbf.png)
+
 ## JetBrains Rider
 
 If you need to develop Avalonia app with JetBrains Rider, go and *vote* on [this issue](https://youtrack.jetbrains.com/issue/RIDER-39247) in their tracker. JetBrains won't do things without their users telling them that they want the feature, so only **YOU** can make it happen.

samples/ControlCatalog/App.xaml

@@ -1,9 +1,7 @@
 <Application xmlns="https://github.com/avaloniaui"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
              x:Class="ControlCatalog.App">
-  <Application.Styles>
+  <Application.Styles>        
-    <StyleInclude Source="avares://Avalonia.Themes.Default/DefaultTheme.xaml"/>
-    <StyleInclude Source="avares://Avalonia.Themes.Default/Accents/BaseLight.xaml"/>
     <StyleInclude Source="avares://Avalonia.Controls.DataGrid/Themes/Default.xaml"/>
     <Style Selector="TextBlock.h1">
       <Setter Property="FontSize" Value="{DynamicResource FontSizeLarge}"/>

samples/ControlCatalog/App.xaml.cs

@@ -1,14 +1,67 @@
+using System;
 using Avalonia;
 using Avalonia.Controls.ApplicationLifetimes;
 using Avalonia.Markup.Xaml;
+using Avalonia.Markup.Xaml.Styling;
+using Avalonia.Styling;
 
 namespace ControlCatalog
 {
     public class App : Application
     {
+        public static Styles FluentDark = new Styles
+        {
+            new StyleInclude(new Uri("resm:Styles?assembly=ControlCatalog"))
+            {
+                Source = new Uri("resm:Avalonia.Themes.Default.Accents.BaseDark.xaml?assembly=Avalonia.Themes.Default")
+            },
+            new StyleInclude(new Uri("resm:Styles?assembly=ControlCatalog"))
+            {
+                Source = new Uri("resm:Avalonia.Themes.Fluent.Accents.FluentDark.xaml?assembly=Avalonia.Themes.Fluent")
+            },
+        };
+
+        public static Styles FluentLight = new Styles
+        {
+            new StyleInclude(new Uri("resm:Styles?assembly=ControlCatalog"))
+            {
+                Source = new Uri("resm:Avalonia.Themes.Default.Accents.BaseLight.xaml?assembly=Avalonia.Themes.Default")
+            },
+            new StyleInclude(new Uri("resm:Styles?assembly=ControlCatalog"))
+            {
+                Source = new Uri("resm:Avalonia.Themes.Fluent.Accents.FluentLight.xaml?assembly=Avalonia.Themes.Fluent")
+            },
+        };
+
+        public static Styles DefaultLight = new Styles
+        {
+            new StyleInclude(new Uri("resm:Styles?assembly=ControlCatalog"))
+            {
+                Source = new Uri("resm:Avalonia.Themes.Default.Accents.BaseLight.xaml?assembly=Avalonia.Themes.Default")
+            },
+            new StyleInclude(new Uri("resm:Styles?assembly=ControlCatalog"))
+            {
+                Source = new Uri("resm:Avalonia.Themes.Default.DefaultTheme.xaml?assembly=Avalonia.Themes.Default")
+            },
+        };
+
+        public static Styles DefaultDark = new Styles
+        {
+            new StyleInclude(new Uri("resm:Styles?assembly=ControlCatalog"))
+            {
+                Source = new Uri("resm:Avalonia.Themes.Default.Accents.BaseDark.xaml?assembly=Avalonia.Themes.Default")
+            },
+            new StyleInclude(new Uri("resm:Styles?assembly=ControlCatalog"))
+            {
+                Source = new Uri("resm:Avalonia.Themes.Default.DefaultTheme.xaml?assembly=Avalonia.Themes.Default")
+            },
+        };
+
         public override void Initialize()
         {
             AvaloniaXamlLoader.Load(this);
+
+            Styles.Insert(0, FluentDark);
         }
 
         public override void OnFrameworkInitializationCompleted()

samples/ControlCatalog/MainView.xaml

@@ -2,7 +2,7 @@
         xmlns:pages="clr-namespace:ControlCatalog.Pages"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         x:Class="ControlCatalog.MainView"
-        Background="{DynamicResource ThemeBackgroundBrush}"
+        Background="Transparent"
         Foreground="{DynamicResource ThemeForegroundBrush}"
         FontSize="{DynamicResource FontSizeNormal}">
   <Grid>
@@ -29,7 +29,8 @@
                ScrollViewer.HorizontalScrollBarVisibility="Disabled">
           <pages:DataGridPage/>
       </TabItem>
-      <TabItem Header="DatePicker"><pages:DatePickerPage/></TabItem>
+      <TabItem Header="CalendarDatePicker">
+        <pages:CalendarDatePickerPage/></TabItem>
       <TabItem Header="Drag+Drop"><pages:DragAndDropPage/></TabItem>
       <TabItem Header="Expander"><pages:ExpanderPage/></TabItem>
       <TabItem Header="Image"
@@ -67,8 +68,16 @@
             <ComboBoxItem>Full Decorations</ComboBoxItem>
           </ComboBox>
           <ComboBox x:Name="Themes" SelectedIndex="0">
-            <ComboBoxItem>Light</ComboBoxItem>
+            <ComboBoxItem>Fluent - Dark</ComboBoxItem>
-            <ComboBoxItem>Dark</ComboBoxItem>
+            <ComboBoxItem>Fluent - Light</ComboBoxItem>
+            <ComboBoxItem>Simple - Light</ComboBoxItem>
+            <ComboBoxItem>Simple - Dark</ComboBoxItem>
+          </ComboBox>
+          <ComboBox x:Name="TransparencyLevels" SelectedIndex="0">
+            <ComboBoxItem>None</ComboBoxItem>
+            <ComboBoxItem>Transparent</ComboBoxItem>
+            <ComboBoxItem>Blur</ComboBoxItem>
+            <ComboBoxItem>AcrylicBlur</ComboBoxItem>
           </ComboBox>
           <ComboBox Items="{Binding WindowStates}" SelectedItem="{Binding WindowState}" />
         </StackPanel>

samples/ControlCatalog/MainView.xaml.cs

@@ -32,30 +32,25 @@ namespace ControlCatalog
 
             }
 
-            var light = new StyleInclude(new Uri("resm:Styles?assembly=ControlCatalog"))
-            {
-                Source = new Uri("resm:Avalonia.Themes.Default.Accents.BaseLight.xaml?assembly=Avalonia.Themes.Default")
-            };
-            var dark = new StyleInclude(new Uri("resm:Styles?assembly=ControlCatalog"))
-            {
-                Source = new Uri("resm:Avalonia.Themes.Default.Accents.BaseDark.xaml?assembly=Avalonia.Themes.Default")
-            };
-
-            
             var themes = this.Find<ComboBox>("Themes");
             themes.SelectionChanged += (sender, e) =>
             {
                 switch (themes.SelectedIndex)
                 {
                     case 0:
-                        Styles[0] = light;
+                        Application.Current.Styles[0] = App.FluentDark;
                         break;
                     case 1:
-                        Styles[0] = dark;
+                        Application.Current.Styles[0] = App.FluentLight;
+                        break;
+                    case 2:
+                        Application.Current.Styles[0] = App.DefaultLight;
+                        break;
+                    case 3:
+                        Application.Current.Styles[0] = App.DefaultDark;
                         break;
                 }
-            };
+            };            
-            Styles.Add(light);
 
             var decorations = this.Find<ComboBox>("Decorations");
             decorations.SelectionChanged += (sender, e) =>
@@ -63,6 +58,13 @@ namespace ControlCatalog
                 if (VisualRoot is Window window)
                     window.SystemDecorations = (SystemDecorations)decorations.SelectedIndex;
             };
+
+            var transparencyLevels = this.Find<ComboBox>("TransparencyLevels");
+            transparencyLevels.SelectionChanged += (sender, e) =>
+            {
+                if (VisualRoot is Window window)
+                    window.TransparencyLevelHint = (WindowTransparencyLevel)transparencyLevels.SelectedIndex;
+            };
         }
 
         protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)

samples/ControlCatalog/MainWindow.xaml

@@ -7,8 +7,7 @@
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:vm="clr-namespace:ControlCatalog.ViewModels"
         xmlns:v="clr-namespace:ControlCatalog.Views"
-        x:Class="ControlCatalog.MainWindow" WindowState="{Binding WindowState, Mode=TwoWay}">
+        x:Class="ControlCatalog.MainWindow" WindowState="{Binding WindowState, Mode=TwoWay}" Background="{DynamicResource SystemControlPageBackgroundAltHighBrush}">
-
   <NativeMenu.Menu>
     <NativeMenu>
       <NativeMenuItem Header="File">

samples/ControlCatalog/Pages/ButtonPage.xaml

@@ -24,7 +24,11 @@
             </Style>
           </Button.Styles>          
         </Button>
-      </StackPanel>
+        <RepeatButton Name="RepeatButton">
+          <TextBlock Name="RepeatButtonTextBlock" Text="Repeat Button: 0" />
+        </RepeatButton>
+        <ToggleButton Content="Toggle Button"/>
+    </StackPanel>
 
       <StackPanel Orientation="Vertical" Spacing="8" Width="150">
         <Button BorderThickness="0">No Border</Button>

samples/ControlCatalog/Pages/ButtonPage.xaml.cs

@@ -5,5 +5,25 @@ namespace ControlCatalog.Pages
 {
     public class ButtonPage : UserControl
     {
+        private int repeatButtonClickCount = 0;
+
+        public ButtonPage()
+        {
+            InitializeComponent();
+
+            this.FindControl<RepeatButton>("RepeatButton").Click += OnRepeatButtonClick;
+        }
+
+        private void InitializeComponent()
+        {
+            AvaloniaXamlLoader.Load(this);
+        }
+
+        public void OnRepeatButtonClick(object sender, object args)
+        {
+            repeatButtonClickCount++;
+            var textBlock = this.FindControl<TextBlock>("RepeatButtonTextBlock");
+            textBlock.Text = $"Repeat Button: {repeatButtonClickCount}";
+        }
     }
 }

samples/ControlCatalog/Pages/DatePickerPage.xaml → samples/ControlCatalog/Pages/CalendarDatePickerPage.xaml

@@ -1,8 +1,8 @@
 <UserControl xmlns="https://github.com/avaloniaui"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
-             x:Class="ControlCatalog.Pages.DatePickerPage">
+             x:Class="ControlCatalog.Pages.CalendarDatePickerPage">
   <StackPanel Orientation="Vertical" Spacing="4">
-    <TextBlock Classes="h1">DatePicker</TextBlock>
+    <TextBlock Classes="h1">CalendarDatePicker</TextBlock>
     <TextBlock Classes="h2">A control for selecting dates with a calendar drop-down</TextBlock>
         
     <StackPanel Orientation="Horizontal"
@@ -12,34 +12,34 @@
       <StackPanel Orientation="Vertical"
                   Width="200">
         <TextBlock Text="SelectedDateFormat: Short"/>
-        <DatePicker Name="DatePicker1"
+        <CalendarDatePicker Name="DatePicker1"
                     SelectedDateFormat="Short"
                     Margin="0,0,0,8"/>
 
         <TextBlock Text="SelectedDateFormat: Long"/>
-        <DatePicker Name="DatePicker2"
+        <CalendarDatePicker Name="DatePicker2"
                     SelectedDateFormat="Long"
                     Margin="0,0,0,8"/>
 
         <TextBlock Text="SelectedDateFormat: Custom"/>
-        <DatePicker Name="DatePicker3"
+        <CalendarDatePicker Name="DatePicker3"
                     SelectedDateFormat="Custom"
                     CustomDateFormatString="ddd, MMM d"
                     Margin="0,0,0,8"/>
 
         <TextBlock Text="Blackout Dates"/>
-        <DatePicker Name="DatePicker4"
+        <CalendarDatePicker Name="DatePicker4"
                     Margin="0,0,0,8"/>
 
-        <DatePicker Margin="0,0,0,8"
+        <CalendarDatePicker Margin="0,0,0,8"
                     Watermark="Watermark"/>
-        <DatePicker Margin="0,0,0,8"
+        <CalendarDatePicker Margin="0,0,0,8"
                     Name="DatePicker5"
                     Watermark="Floating Watermark"
                     UseFloatingWatermark="True"/>
                 
         <TextBlock Text="Disabled"/>
-        <DatePicker IsEnabled="False"/>
+        <CalendarDatePicker IsEnabled="False"/>
       </StackPanel>
 
     </StackPanel> 

samples/ControlCatalog/Pages/DatePickerPage.xaml.cs → samples/ControlCatalog/Pages/CalendarDatePickerPage.xaml.cs

@@ -4,17 +4,17 @@ using System;
 
 namespace ControlCatalog.Pages
 {
-    public class DatePickerPage : UserControl
+    public class CalendarDatePickerPage : UserControl
     {
-        public DatePickerPage()
+        public CalendarDatePickerPage()
         {
             InitializeComponent();
             
-            var dp1 = this.FindControl<DatePicker>("DatePicker1");
+            var dp1 = this.FindControl<CalendarDatePicker>("DatePicker1");
-            var dp2 = this.FindControl<DatePicker>("DatePicker2");
+            var dp2 = this.FindControl<CalendarDatePicker>("DatePicker2");
-            var dp3 = this.FindControl<DatePicker>("DatePicker3");
+            var dp3 = this.FindControl<CalendarDatePicker>("DatePicker3");
-            var dp4 = this.FindControl<DatePicker>("DatePicker4");
+            var dp4 = this.FindControl<CalendarDatePicker>("DatePicker4");
-            var dp5 = this.FindControl<DatePicker>("DatePicker5");
+            var dp5 = this.FindControl<CalendarDatePicker>("DatePicker5");
 
             dp1.SelectedDate = DateTime.Today;
             dp2.SelectedDate = DateTime.Today.AddDays(10);

samples/ControlCatalog/Pages/ComboBoxPage.xaml

@@ -6,7 +6,7 @@
     <TextBlock Classes="h2">A drop-down list.</TextBlock>
 
     <StackPanel Orientation="Horizontal" HorizontalAlignment="Center" Margin="0 16 0 0" Spacing="8">
-      <ComboBox SelectedIndex="0">
+      <ComboBox PlaceholderText="Pick an Item">
         <ComboBoxItem>Inline Items</ComboBoxItem>
         <ComboBoxItem>Inline Item 2</ComboBoxItem>
         <ComboBoxItem>Inline Item 3</ComboBoxItem>

samples/ControlCatalog/Pages/DialogsPage.xaml

@@ -11,5 +11,7 @@
       <Button Name="DecoratedWindowDialog">Decorated window (dialog)</Button>
       <Button Name="Dialog">Dialog</Button>
       <Button Name="DialogNoTaskbar">Dialog (No taskbar icon)</Button>
+      <Button Name="OwnedWindow">Owned window</Button>
+      <Button Name="OwnedWindowNoTaskbar">Owned window (No taskbar icon)</Button>
   </StackPanel>
 </UserControl>

samples/ControlCatalog/Pages/DialogsPage.xaml.cs

@@ -93,6 +93,21 @@ namespace ControlCatalog.Pages
                 window.ShowInTaskbar = false;
                 window.ShowDialog(GetWindow());
             };
+            this.FindControl<Button>("OwnedWindow").Click += delegate
+            {
+                var window = CreateSampleWindow();
+
+                window.Show(GetWindow());
+            };
+
+            this.FindControl<Button>("OwnedWindowNoTaskbar").Click += delegate
+            {
+                var window = CreateSampleWindow();
+
+                window.ShowInTaskbar = false;
+
+                window.Show(GetWindow());
+            };
         }
 
         private Window CreateSampleWindow()

samples/ControlCatalog/Pages/DragAndDropPage.xaml

@@ -9,9 +9,15 @@
                 Margin="0,16,0,0"
                 HorizontalAlignment="Center"
                 Spacing="16">
-            <Border BorderBrush="{DynamicResource ThemeAccentBrush}" BorderThickness="2" Padding="16" Name="DragMe">
+            <StackPanel>
-                <TextBlock Name="DragState">Drag Me</TextBlock>
+                <Border BorderBrush="{DynamicResource ThemeAccentBrush}" BorderThickness="2" Padding="16" Name="DragMeText">
-            </Border>
+                  <TextBlock Name="DragStateText">Drag Me</TextBlock>
+                </Border>
+                <Border BorderBrush="{DynamicResource ThemeAccentBrush}" BorderThickness="2" Padding="16" Name="DragMeCustom">
+                  <TextBlock Name="DragStateCustom">Drag Me (custom)</TextBlock>
+                </Border>
+            </StackPanel>
+
             <Border Background="{DynamicResource ThemeAccentBrush2}" Padding="16" 
                     DragDrop.AllowDrop="True">
                 <TextBlock Name="DropState">Drop some text or files here</TextBlock>

samples/ControlCatalog/Pages/DragAndDropPage.xaml.cs

@@ -3,69 +3,85 @@ using Avalonia.Input;
 using Avalonia.Markup.Xaml;
 using System;
 using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Reflection;
 using System.Text;
 
 namespace ControlCatalog.Pages
 {
     public class DragAndDropPage : UserControl
     {
-        private TextBlock _DropState;
+        TextBlock _DropState;
-        private TextBlock _DragState;
+        private const string CustomFormat = "application/xxx-avalonia-controlcatalog-custom";
-        private Border _DragMe;
-        private int DragCount = 0;
-
         public DragAndDropPage()
         {
             this.InitializeComponent();
+            _DropState = this.Find<TextBlock>("DropState");
 
-            _DragMe.PointerPressed += DoDrag;
+            int textCount = 0;
+            SetupDnd("Text", d => d.Set(DataFormats.Text,
+                $"Text was dragged {++textCount} times"));
 
-            AddHandler(DragDrop.DropEvent, Drop);
+            SetupDnd("Custom", d => d.Set(CustomFormat, "Test123"));
-            AddHandler(DragDrop.DragOverEvent, DragOver);
         }
 
-        private async void DoDrag(object sender, Avalonia.Input.PointerPressedEventArgs e)
+        void SetupDnd(string suffix, Action<DataObject> factory, DragDropEffects effects = DragDropEffects.Copy)
         {
-            DataObject dragData = new DataObject();
+            var dragMe = this.Find<Border>("DragMe" + suffix);
-            dragData.Set(DataFormats.Text, $"You have dragged text {++DragCount} times");
+            var dragState = this.Find<TextBlock>("DragState"+suffix);
 
-            var result = await DragDrop.DoDragDrop(e, dragData, DragDropEffects.Copy);
+            async void DoDrag(object sender, Avalonia.Input.PointerPressedEventArgs e)
-            switch(result)
             {
-                case DragDropEffects.Copy:
+                var dragData = new DataObject();
-                    _DragState.Text = "The text was copied"; break;
+                factory(dragData);
-                case DragDropEffects.Link:
+
-                    _DragState.Text = "The text was linked"; break;
+                var result = await DragDrop.DoDragDrop(e, dragData, DragDropEffects.Copy);
-                case DragDropEffects.None:
+                switch (result)
-                    _DragState.Text = "The drag operation was canceled"; break;
+                {
+                    case DragDropEffects.Copy:
+                        dragState.Text = "Data was copied";
+                        break;
+                    case DragDropEffects.Link:
+                        dragState.Text = "Data was linked";
+                        break;
+                    case DragDropEffects.None:
+                        dragState.Text = "The drag operation was canceled";
+                        break;
+                }
             }
-        }
 
-        private void DragOver(object sender, DragEventArgs e)
+            void DragOver(object sender, DragEventArgs e)
-        {
+            {
-            // Only allow Copy or Link as Drop Operations.
+                // Only allow Copy or Link as Drop Operations.
-            e.DragEffects = e.DragEffects & (DragDropEffects.Copy | DragDropEffects.Link);
+                e.DragEffects = e.DragEffects & (DragDropEffects.Copy | DragDropEffects.Link);
 
-            // Only allow if the dragged data contains text or filenames.
+                // Only allow if the dragged data contains text or filenames.
-            if (!e.Data.Contains(DataFormats.Text) && !e.Data.Contains(DataFormats.FileNames))
+                if (!e.Data.Contains(DataFormats.Text)
-                e.DragEffects = DragDropEffects.None; 
+                    && !e.Data.Contains(DataFormats.FileNames)
-        }
+                    && !e.Data.Contains(CustomFormat))
+                    e.DragEffects = DragDropEffects.None;
+            }
 
-        private void Drop(object sender, DragEventArgs e)
+            void Drop(object sender, DragEventArgs e)
-        {
+            {
-            if (e.Data.Contains(DataFormats.Text))
+                if (e.Data.Contains(DataFormats.Text))
-                _DropState.Text = e.Data.GetText();
+                    _DropState.Text = e.Data.GetText();
-            else if (e.Data.Contains(DataFormats.FileNames))
+                else if (e.Data.Contains(DataFormats.FileNames))
-                _DropState.Text = string.Join(Environment.NewLine, e.Data.GetFileNames());
+                    _DropState.Text = string.Join(Environment.NewLine, e.Data.GetFileNames());
+                else if (e.Data.Contains(CustomFormat))
+                    _DropState.Text = "Custom: " + e.Data.Get(CustomFormat);
+            }
+
+            dragMe.PointerPressed += DoDrag;
+
+            AddHandler(DragDrop.DropEvent, Drop);
+            AddHandler(DragDrop.DragOverEvent, DragOver);
         }
 
         private void InitializeComponent()
         {
             AvaloniaXamlLoader.Load(this);
-
-            _DropState = this.Find<TextBlock>("DropState");
-            _DragState = this.Find<TextBlock>("DragState");
-            _DragMe = this.Find<Border>("DragMe");
         }
     }
 }

samples/ControlCatalog/Pages/NumericUpDownPage.xaml

@@ -50,22 +50,22 @@
         <TextBlock Grid.Row="4" Grid.Column="0" VerticalAlignment="Center" Margin="2">Text:</TextBlock>
         <TextBox Grid.Row="4" Grid.Column="1" Text="{Binding #upDown.Text}" VerticalAlignment="Center" Margin="2" />
       </Grid>
-      <Grid Grid.Row="0" Grid.Column="2" Margin="10,2,2,2" RowDefinitions="Auto,Auto,Auto,Auto,Auto" ColumnDefinitions="Auto, 120">
+      <Grid Grid.Row="0" Grid.Column="2" Margin="10,2,2,2" RowDefinitions="Auto,Auto,Auto,Auto,Auto" ColumnDefinitions="Auto, Auto">
         <TextBlock Grid.Row="0" Grid.Column="0" VerticalAlignment="Center" Margin="10,2,2,2">Minimum:</TextBlock>
         <NumericUpDown Grid.Row="0" Grid.Column="1" Value="{Binding #upDown.Minimum}"
-                       CultureInfo="{Binding #upDown.CultureInfo}" VerticalAlignment="Center" Margin="2" Width="70" HorizontalAlignment="Center"/>
+                       CultureInfo="{Binding #upDown.CultureInfo}" VerticalAlignment="Center" Margin="2" HorizontalAlignment="Center"/>
 
         <TextBlock Grid.Row="1" Grid.Column="0" VerticalAlignment="Center" Margin="10,2,2,2">Maximum:</TextBlock>
         <NumericUpDown Grid.Row="1" Grid.Column="1" Value="{Binding #upDown.Maximum}"
-                       CultureInfo="{Binding #upDown.CultureInfo}" VerticalAlignment="Center" Margin="2" Width="70" HorizontalAlignment="Center"/>
+                       CultureInfo="{Binding #upDown.CultureInfo}" VerticalAlignment="Center" Margin="2" HorizontalAlignment="Center"/>
 
         <TextBlock Grid.Row="2" Grid.Column="0" VerticalAlignment="Center" Margin="10,2,2,2">Increment:</TextBlock>
         <NumericUpDown Grid.Row="2" Grid.Column="1" Value="{Binding #upDown.Increment}" VerticalAlignment="Center"
-                       Margin="2" Width="70" HorizontalAlignment="Center"/>
+                       Margin="2" HorizontalAlignment="Center"/>
 
         <TextBlock Grid.Row="3" Grid.Column="0" VerticalAlignment="Center" Margin="10,2,2,2">Value:</TextBlock>
         <NumericUpDown Grid.Row="3" Grid.Column="1" Value="{Binding #upDown.Value}" VerticalAlignment="Center"
-                       Margin="2" Width="70" HorizontalAlignment="Center"/>
+                       Margin="2" HorizontalAlignment="Center"/>
 
       </Grid>
     </Grid>
@@ -73,7 +73,7 @@
     <StackPanel Margin="2,10,2,2" Orientation="Horizontal" Spacing="10">
       <TextBlock FontSize="14" FontWeight="Bold" VerticalAlignment="Center">Usage of NumericUpDown:</TextBlock>
       <NumericUpDown Name="upDown" Minimum="0" Maximum="10" Increment="0.5"
-                     CultureInfo="en-US" VerticalAlignment="Center" Width="100"
+                     CultureInfo="en-US" VerticalAlignment="Center"
                      Watermark="Enter text" FormatString="{Binding SelectedFormat.Value}"/>
     </StackPanel>
 

samples/ControlCatalog/Pages/SliderPage.xaml

@@ -9,12 +9,14 @@
       <Slider Value="0"
               Minimum="0"
               Maximum="100"
+              TickFrequency="10"
               Width="300"/>
       <Slider Value="0"
               Minimum="0"
               Maximum="100"
               Orientation="Vertical"
               IsSnapToTickEnabled="True"
+              TickPlacement="Outside"
               TickFrequency="10"
               Height="300"/>
     </StackPanel>

samples/ControlCatalog/Pages/ToolTipPage.xaml

@@ -18,7 +18,7 @@
                     ToolTip.Tip="This is a ToolTip">
                 <TextBlock>Hover Here</TextBlock>
             </Border>
-            <CheckBox Grid.Column="1"
+            <ToggleSwitch Grid.Column="1"
                       Margin="5"
                       Grid.Row="0"
                       IsChecked="{Binding ElementName=Border, Path=(ToolTip.IsOpen)}"

samples/ControlCatalog/Pages/TreeViewPage.xaml

@@ -19,8 +19,8 @@
         </TreeView>
 
         <Button Command="{Binding AddItemCommand}">Add</Button>
-
         <Button Command="{Binding RemoveItemCommand}">Remove</Button>
+        <Button Command="{Binding SelectRandomItemCommand}">Select Random</Button>
 
         <ComboBox SelectedIndex="{Binding SelectionMode, Mode=TwoWay}">
           <ComboBoxItem>Single</ComboBoxItem>

samples/ControlCatalog/Pages/TreeViewPage.xaml.cs

@@ -1,9 +1,6 @@
-using System.Collections.ObjectModel;
-using System.Linq;
-using System.Reactive;
 using Avalonia.Controls;
 using Avalonia.Markup.Xaml;
-using ReactiveUI;
+using ControlCatalog.ViewModels;
 
 namespace ControlCatalog.Pages
 {
@@ -12,105 +9,12 @@ namespace ControlCatalog.Pages
         public TreeViewPage()
         {
             InitializeComponent();
-            DataContext = new PageViewModel();
+            DataContext = new TreeViewPageViewModel();
         }
 
         private void InitializeComponent()
         {
             AvaloniaXamlLoader.Load(this);
         }
-
-        private class PageViewModel : ReactiveObject
-        {
-            private SelectionMode _selectionMode;
-
-            public PageViewModel()
-            {
-                Node root = new Node();
-                Items = root.Children;
-                Selection = new SelectionModel();
-
-                AddItemCommand = ReactiveCommand.Create(() =>
-                {
-                    Node parentItem = Selection.SelectedItems.Count > 0 ?
-                        (Node)Selection.SelectedItems[0] : root;
-                    parentItem.AddNewItem();
-                });
-
-                RemoveItemCommand = ReactiveCommand.Create(() =>
-                {
-                    while (Selection.SelectedItems.Count > 0)
-                    {
-                        Node lastItem = (Node)Selection.SelectedItems[0];
-                        RecursiveRemove(Items, lastItem);
-                        Selection.DeselectAt(Selection.SelectedIndices[0]);
-                    }
-
-                    bool RecursiveRemove(ObservableCollection<Node> items, Node selectedItem)
-                    {
-                        if (items.Remove(selectedItem))
-                        {
-                            return true;
-                        }
-
-                        foreach (Node item in items)
-                        {
-                            if (item.AreChildrenInitialized && RecursiveRemove(item.Children, selectedItem))
-                            {
-                                return true;
-                            }
-                        }
-
-                        return false;
-                    }
-                });
-            }
-
-            public ObservableCollection<Node> Items { get; }
-
-            public SelectionModel Selection { get; }
-
-            public ReactiveCommand<Unit, Unit> AddItemCommand { get; }
-
-            public ReactiveCommand<Unit, Unit> RemoveItemCommand { get; }
-
-            public SelectionMode SelectionMode
-            {
-                get => _selectionMode;
-                set
-                {
-                    Selection.ClearSelection();
-                    this.RaiseAndSetIfChanged(ref _selectionMode, value);
-                }
-            }
-        }
-
-        private class Node
-        {
-            private int _counter;
-            private ObservableCollection<Node> _children;
-
-            public string Header { get; private set; }
-
-            public bool AreChildrenInitialized => _children != null;
-
-            public ObservableCollection<Node> Children
-            {
-                get
-                {
-                    if (_children == null)
-                    {
-                        _children = new ObservableCollection<Node>(Enumerable.Range(1, 10).Select(i => CreateNewNode()));
-                    }
-                    return _children;
-                }
-            }
-
-            public void AddNewItem() => Children.Add(CreateNewNode());
-
-            public override string ToString() => Header;
-
-            private Node CreateNewNode() => new Node { Header = $"Item {_counter++}" };
-        }
     }
 }

samples/ControlCatalog/ViewModels/TreeViewPageViewModel.cs

@@ -0,0 +1,126 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Linq;
+using System.Reactive;
+using Avalonia.Controls;
+using ReactiveUI;
+
+namespace ControlCatalog.ViewModels
+{
+    public class TreeViewPageViewModel : ReactiveObject
+    {
+        private readonly Node _root;
+        private SelectionMode _selectionMode;
+
+        public TreeViewPageViewModel()
+        {
+            _root = new Node();
+
+            Items = _root.Children;
+            Selection = new SelectionModel();
+            Selection.SelectionChanged += SelectionChanged;
+
+            AddItemCommand = ReactiveCommand.Create(AddItem);
+            RemoveItemCommand = ReactiveCommand.Create(RemoveItem);
+            SelectRandomItemCommand = ReactiveCommand.Create(SelectRandomItem);
+        }
+
+        public ObservableCollection<Node> Items { get; }
+        public SelectionModel Selection { get; }
+        public ReactiveCommand<Unit, Unit> AddItemCommand { get; }
+        public ReactiveCommand<Unit, Unit> RemoveItemCommand { get; }
+        public ReactiveCommand<Unit, Unit> SelectRandomItemCommand { get; }
+
+        public SelectionMode SelectionMode
+        {
+            get => _selectionMode;
+            set
+            {
+                Selection.ClearSelection();
+                this.RaiseAndSetIfChanged(ref _selectionMode, value);
+            }
+        }
+
+        private void AddItem()
+        {
+            var parentItem = Selection.SelectedItems.Count > 0 ? (Node)Selection.SelectedItems[0] : _root;
+            parentItem.AddItem();
+        }
+
+        private void RemoveItem()
+        {
+            while (Selection.SelectedItems.Count > 0)
+            {
+                Node lastItem = (Node)Selection.SelectedItems[0];
+                RecursiveRemove(Items, lastItem);
+                Selection.DeselectAt(Selection.SelectedIndices[0]);
+            }
+
+            bool RecursiveRemove(ObservableCollection<Node> items, Node selectedItem)
+            {
+                if (items.Remove(selectedItem))
+                {
+                    return true;
+                }
+
+                foreach (Node item in items)
+                {
+                    if (item.AreChildrenInitialized && RecursiveRemove(item.Children, selectedItem))
+                    {
+                        return true;
+                    }
+                }
+
+                return false;
+            }
+        }
+
+        private void SelectRandomItem()
+        {
+            var random = new Random();
+            var depth = random.Next(4);
+            var indexes = Enumerable.Range(0, 4).Select(x => random.Next(10));
+            var path = new IndexPath(indexes);
+            Selection.SelectedIndex = path;
+        }
+
+        private void SelectionChanged(object sender, SelectionModelSelectionChangedEventArgs e)
+        {
+            var selected = string.Join(",", e.SelectedIndices);
+            var deselected = string.Join(",", e.DeselectedIndices);
+            System.Diagnostics.Debug.WriteLine($"Selected '{selected}', Deselected '{deselected}'");
+        }
+
+        public class Node
+        {
+            private ObservableCollection<Node> _children;
+            private int _childIndex = 10;
+
+            public Node()
+            {
+                Header = "Item";
+            }
+
+            public Node(Node parent, int index)
+            {
+                Parent = parent;
+                Header = parent.Header + ' ' + index;
+            }
+
+            public Node Parent { get; }
+            public string Header { get; }
+            public bool AreChildrenInitialized => _children != null;
+            public ObservableCollection<Node> Children => _children ??= CreateChildren();
+            public void AddItem() => Children.Add(new Node(this, _childIndex++));
+            public void RemoveItem(Node child) => Children.Remove(child);
+            public override string ToString() => Header;
+
+            private ObservableCollection<Node> CreateChildren()
+            {
+                return new ObservableCollection<Node>(
+                    Enumerable.Range(0, 10).Select(i => new Node(this, i)));
+            }
+        }
+    }
+}

samples/Directory.Build.props

@@ -1,6 +1,7 @@
 <Project>
   <PropertyGroup>
       <IsPackable>false</IsPackable>
+      <AvaloniaPreviewerNetCoreToolPath>$(MSBuildThisFileDirectory)..\src\tools\Avalonia.Designer.HostApp\bin\Debug\netcoreapp2.0\Avalonia.Designer.HostApp.dll</AvaloniaPreviewerNetCoreToolPath>
   </PropertyGroup>
   <Import Project="..\build\SharedVersion.props" />
 </Project>

samples/RenderDemo/Controls/LineBoundsDemoControl.cs

@@ -0,0 +1,53 @@
+using System;
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Media;
+using Avalonia.Rendering.SceneGraph;
+using Avalonia.Threading;
+
+namespace RenderDemo.Controls
+{
+    public class LineBoundsDemoControl : Control
+    {
+        static LineBoundsDemoControl()
+        {
+            AffectsRender<LineBoundsDemoControl>(AngleProperty);
+        }
+
+        public LineBoundsDemoControl()
+        {
+            var timer = new DispatcherTimer();
+            timer.Interval = TimeSpan.FromSeconds(1 / 60.0);
+            timer.Tick += (sender, e) => Angle += Math.PI / 360;
+            timer.Start();
+        }
+
+        public static readonly StyledProperty<double> AngleProperty =
+            AvaloniaProperty.Register<LineBoundsDemoControl, double>(nameof(Angle));        
+
+        public double Angle
+        {
+            get => GetValue(AngleProperty);
+            set => SetValue(AngleProperty, value);
+        }
+
+        public override void Render(DrawingContext drawingContext)
+        {
+            var lineLength = Math.Sqrt((100 * 100) + (100 * 100));
+
+            var diffX = LineBoundsHelper.CalculateAdjSide(Angle, lineLength);
+            var diffY = LineBoundsHelper.CalculateOppSide(Angle, lineLength);
+
+
+            var p1 = new Point(200, 200);
+            var p2 = new Point(p1.X + diffX, p1.Y + diffY);
+
+            var pen = new Pen(Brushes.Green, 20, lineCap: PenLineCap.Square);
+            var boundPen = new Pen(Brushes.Black);
+
+            drawingContext.DrawLine(pen, p1, p2);
+
+            drawingContext.DrawRectangle(boundPen, LineBoundsHelper.CalculateBounds(p1, p2, pen));
+        }
+    }
+}

samples/RenderDemo/MainWindow.xaml

@@ -29,6 +29,9 @@
       <TabItem Header="Animations">
         <pages:AnimationsPage/>
       </TabItem>
+      <TabItem Header="Transitions">
+        <pages:TransitionsPage/>
+      </TabItem>
       <TabItem Header="Clipping">
         <pages:ClippingPage/>
       </TabItem>
@@ -44,6 +47,9 @@
       <TabItem Header="GlyphRun">
         <pages:GlyphRunPage/>
       </TabItem>
+      <TabItem Header="LineBounds">
+        <pages:LineBoundsPage />
+      </TabItem>
     </TabControl>
   </DockPanel>
 </Window>

samples/RenderDemo/Pages/LineBoundsPage.xaml

@@ -0,0 +1,9 @@
+<UserControl xmlns="https://github.com/avaloniaui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+             mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
+             xmlns:controls="clr-namespace:RenderDemo.Controls"
+             x:Class="RenderDemo.Pages.LineBoundsPage">
+  <controls:LineBoundsDemoControl />
+</UserControl>

samples/RenderDemo/Pages/LineBoundsPage.xaml.cs

@@ -0,0 +1,19 @@
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Markup.Xaml;
+
+namespace RenderDemo.Pages
+{
+    public class LineBoundsPage : UserControl
+    {
+        public LineBoundsPage()
+        {
+            this.InitializeComponent();
+        }
+
+        private void InitializeComponent()
+        {
+            AvaloniaXamlLoader.Load(this);
+        }
+    }
+}

samples/RenderDemo/Pages/TransitionsPage.xaml

@@ -0,0 +1,101 @@
+<UserControl 
+  xmlns="https://github.com/avaloniaui" 
+  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
+  x:Class="RenderDemo.Pages.TransitionsPage">
+  <UserControl.Styles>
+    <Styles>
+      <Styles.Resources>
+        <Template x:Key="Acorn">
+          <Path Fill="White" Stretch="Uniform"
+                Data="F1 M 16.6309,18.6563C 17.1309,
+                8.15625 29.8809,14.1563 29.8809,
+                14.1563C 30.8809,11.1563 34.1308,
+                11.4063 34.1308,11.4063C 33.5,12 
+                34.6309,13.1563 34.6309,13.1563C 
+                32.1309,13.1562 31.1309,14.9062 
+                31.1309,14.9062C 41.1309,23.9062
+                32.6309,27.9063 32.6309,27.9062C 
+                24.6309,24.9063 21.1309,22.1562 
+                16.6309,18.6563 Z M 16.6309,19.9063C
+                21.6309,24.1563 25.1309,26.1562 
+                31.6309,28.6562C 31.6309,28.6562
+                26.3809,39.1562 18.3809,36.1563C
+                18.3809,36.1563 18,38 16.3809,36.9063C 
+                15,36 16.3809,34.9063 16.3809,34.9063C
+                16.3809,34.9063 10.1309,30.9062 16.6309,19.9063 Z"/>
+        </Template>
+        <Template x:Key="Heart">
+          <Path Fill="Red" Stretch="Uniform" Data="
+          M 272.70141,238.71731 
+          C 206.46141,238.71731 152.70146,292.4773 152.70146,358.71731 
+          C 152.70146,493.47282 288.63461,528.80461 381.26391,662.02535 
+          C 468.83815,529.62199 609.82641,489.17075 609.82641,358.71731 
+          C 609.82641,292.47731 556.06651,238.7173 489.82641,238.71731 
+          C 441.77851,238.71731 400.42481,267.08774 381.26391,307.90481 
+          C 362.10311,267.08773 320.74941,238.7173 272.70141,238.71731 z "/>
+        </Template>
+      </Styles.Resources>
+
+      <Style Selector="Border.Test">
+        <Setter Property="Margin" Value="15"/>
+        <Setter Property="Width" Value="100"/>
+        <Setter Property="Height" Value="100"/>
+        <Setter Property="Child" Value="{StaticResource Acorn}"/>
+        <Setter Property="Transitions">
+          <Transitions>
+            <TransformOperationsTransition Property="RenderTransform"  Duration="0:0:1" />
+          </Transitions>
+        </Setter>
+        <Setter Property="RenderTransform" Value="none" />
+      </Style>
+
+      <Style Selector="Border.Rect1:pointerover">
+        <Setter Property="RenderTransform" Value="rotate(120deg) scale(1.5)" />
+      </Style>
+
+      <Style Selector="Border.Rect2:pointerover">
+        <Setter Property="RenderTransform" Value="scale(0.8)" />
+      </Style>
+
+      <Style Selector="Border.Rect3">
+        <Setter Property="Child" Value="{StaticResource Heart}"/>
+      </Style>
+
+      <Style Selector="Border.Rect3:pointerover">
+        <Setter Property="RenderTransform" Value="rotate(1turn)" />
+      </Style>
+
+      <Style Selector="Border.Rect4:pointerover">
+        <Setter Property="RenderTransform" Value="translateY(-100px)" />
+      </Style>
+
+      <Style Selector="Border.Rect5:pointerover">
+        <Setter Property="RenderTransform" Value="skewX(-20deg)" />
+      </Style>
+
+      <Style Selector="Border.Rect5:pointerover">
+        <Setter Property="RenderTransform" Value="skewX(-20deg)" />
+      </Style>
+
+    </Styles>
+  </UserControl.Styles>
+
+  <Grid>
+    <StackPanel HorizontalAlignment="Center" VerticalAlignment="Center" ClipToBounds="False">
+      <StackPanel.Clock>
+        <Clock />
+      </StackPanel.Clock>
+      <StackPanel Orientation="Horizontal" VerticalAlignment="Center">
+        <TextBlock VerticalAlignment="Center">Hover to activate Transform Keyframe Animations.</TextBlock>
+        <Button Content="{Binding PlayStateText}" Command="{Binding TogglePlayState}" Click="ToggleClock" />
+      </StackPanel>
+      <WrapPanel ClipToBounds="False">
+        <Border Classes="Test Rect1" Background="DarkRed"/>
+        <Border Classes="Test Rect2" Background="Magenta"/>
+        <Border Classes="Test Rect3"/>
+        <Border Classes="Test Rect4" Background="Navy"/>
+        <Border Classes="Test Rect5" Background="SeaGreen"/>
+      </WrapPanel>
+    </StackPanel>
+  </Grid>
+</UserControl>

samples/RenderDemo/Pages/TransitionsPage.xaml.cs

@@ -0,0 +1,37 @@
+using Avalonia.Animation;
+using Avalonia.Controls;
+using Avalonia.Interactivity;
+using Avalonia.Markup.Xaml;
+using RenderDemo.ViewModels;
+
+namespace RenderDemo.Pages
+{
+    public class TransitionsPage : UserControl
+    {
+        public TransitionsPage()
+        {
+            InitializeComponent();
+            this.DataContext = new AnimationsPageViewModel();
+        }
+
+        private void InitializeComponent()
+        {
+            AvaloniaXamlLoader.Load(this);
+        }
+
+        private void ToggleClock(object sender, RoutedEventArgs args)
+        {
+            var button = sender as Button;
+            var clock = button.Clock;
+
+            if (clock.PlayState == PlayState.Run)
+            {
+                clock.PlayState = PlayState.Pause;
+            }
+            else if (clock.PlayState == PlayState.Pause)
+            {
+                clock.PlayState = PlayState.Run;
+            }
+        }
+    }
+}

samples/RenderDemo/RenderDemo.csproj

@@ -3,6 +3,9 @@
     <OutputType>Exe</OutputType>
     <TargetFramework>netcoreapp3.1</TargetFramework>
   </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="..\..\src\Avalonia.Visuals\Rendering\SceneGraph\LineBoundsHelper.cs" Link="LineBoundsHelper.cs" />
+  </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\src\Avalonia.Diagnostics\Avalonia.Diagnostics.csproj" />
     <ProjectReference Include="..\..\src\Linux\Avalonia.LinuxFramebuffer\Avalonia.LinuxFramebuffer.csproj" />

src/Android/Avalonia.Android/Platform/ClipboardImpl.cs

@@ -43,5 +43,11 @@ namespace Avalonia.Android.Platform
 
             return Task.FromResult<object>(null);
         }
+
+        public Task SetDataObjectAsync(IDataObject data) => throw new PlatformNotSupportedException();
+
+        public Task<string[]> GetFormatsAsync() => throw new PlatformNotSupportedException();
+
+        public Task<object> GetDataAsync(string format) => throw new PlatformNotSupportedException();
     }
 }

src/Avalonia.Animation/Animatable.cs

@@ -1,10 +1,10 @@
 using System;
+using System.Collections;
 using System.Collections.Generic;
-using System.Linq;
+using System.Collections.Specialized;
-using System.Reactive.Linq;
-using Avalonia.Collections;
 using Avalonia.Data;
-using Avalonia.Animation.Animators;
+
+#nullable enable
 
 namespace Avalonia.Animation
 {
@@ -13,9 +13,24 @@ namespace Avalonia.Animation
     /// </summary>
     public class Animatable : AvaloniaObject
     {
+        /// <summary>
+        /// Defines the <see cref="Clock"/> property.
+        /// </summary>
         public static readonly StyledProperty<IClock> ClockProperty =
             AvaloniaProperty.Register<Animatable, IClock>(nameof(Clock), inherits: true);
 
+        /// <summary>
+        /// Defines the <see cref="Transitions"/> property.
+        /// </summary>
+        public static readonly StyledProperty<Transitions?> TransitionsProperty =
+            AvaloniaProperty.Register<Animatable, Transitions?>(nameof(Transitions));
+
+        private bool _transitionsEnabled = true;
+        private Dictionary<ITransition, TransitionState>? _transitionState;
+
+        /// <summary>
+        /// Gets or sets the clock which controls the animations on the control.
+        /// </summary>
         public IClock Clock
         {
             get => GetValue(ClockProperty);
@@ -23,72 +38,196 @@ namespace Avalonia.Animation
         }
 
         /// <summary>
-        /// Defines the <see cref="Transitions"/> property.
+        /// Gets or sets the property transitions for the control.
         /// </summary>
-        public static readonly DirectProperty<Animatable, Transitions> TransitionsProperty =
+        public Transitions? Transitions
-            AvaloniaProperty.RegisterDirect<Animatable, Transitions>(
+        {
-                nameof(Transitions),
+            get => GetValue(TransitionsProperty);
-                o => o.Transitions,
+            set => SetValue(TransitionsProperty, value);
-                (o, v) => o.Transitions = v);
+        }
 
-        private Transitions _transitions;
+        /// <summary>
+        /// Enables transitions for the control.
+        /// </summary>
+        /// <remarks>
+        /// This method should not be called from user code, it will be called automatically by the framework
+        /// when a control is added to the visual tree.
+        /// </remarks>
+        protected void EnableTransitions()
+        {
+            if (!_transitionsEnabled)
+            {
+                _transitionsEnabled = true;
 
-        private Dictionary<AvaloniaProperty, IDisposable> _previousTransitions;
+                if (Transitions is object)
+                {
+                    AddTransitions(Transitions);
+                }
+            }
+        }
 
         /// <summary>
-        /// Gets or sets the property transitions for the control.
+        /// Disables transitions for the control.
         /// </summary>
-        public Transitions Transitions
+        /// <remarks>
+        /// This method should not be called from user code, it will be called automatically by the framework
+        /// when a control is added to the visual tree.
+        /// </remarks>
+        protected void DisableTransitions()
+        {
+            if (_transitionsEnabled)
+            {
+                _transitionsEnabled = false;
+
+                if (Transitions is object)
+                {
+                    RemoveTransitions(Transitions);
+                }
+            }
+        }
+
+        protected sealed override void OnPropertyChangedCore<T>(AvaloniaPropertyChangedEventArgs<T> change)
         {
-            get
+            if (change.Property == TransitionsProperty && change.IsEffectiveValueChange)
             {
-                if (_transitions is null)
+                var oldTransitions = change.OldValue.GetValueOrDefault<Transitions>();
-                    _transitions = new Transitions();
+                var newTransitions = change.NewValue.GetValueOrDefault<Transitions>();
 
-                if (_previousTransitions is null)
+                if (newTransitions is object)
-                    _previousTransitions = new Dictionary<AvaloniaProperty, IDisposable>();
+                {
+                    newTransitions.CollectionChanged += TransitionsCollectionChanged;
+                    AddTransitions(newTransitions);
+                }
 
-                return _transitions;
+                if (oldTransitions is object)
+                {
+                    oldTransitions.CollectionChanged -= TransitionsCollectionChanged;
+                    RemoveTransitions(oldTransitions);
+                }
             }
-            set
+            else if (_transitionsEnabled &&
+                     Transitions is object &&
+                     _transitionState is object &&
+                     !change.Property.IsDirect &&
+                     change.Priority > BindingPriority.Animation)
             {
-                if (value is null)
+                for (var i = Transitions.Count -1; i >= 0; --i)
-                    return;
+                {
+                    var transition = Transitions[i];
+
+                    if (transition.Property == change.Property)
+                    {
+                        var state = _transitionState[transition];
+                        var oldValue = state.BaseValue;
+                        var newValue = GetAnimationBaseValue(transition.Property);
 
-                if (_previousTransitions is null)
+                        if (!Equals(oldValue, newValue))
-                    _previousTransitions = new Dictionary<AvaloniaProperty, IDisposable>();
+                        {
+                            state.BaseValue = newValue;
 
-                SetAndRaise(TransitionsProperty, ref _transitions, value);
+                            // We need to transition from the current animated value if present,
+                            // instead of the old base value.
+                            var animatedValue = GetValue(transition.Property);
+
+                            if (!Equals(newValue, animatedValue))
+                            {
+                                oldValue = animatedValue;
+                            }
+
+                            state.Instance?.Dispose();
+                            state.Instance = transition.Apply(
+                                this,
+                                Clock ?? AvaloniaLocator.Current.GetService<IGlobalClock>(),
+                                oldValue,
+                                newValue);
+                            return;
+                        }
+                    }
+                }
+            }
+
+            base.OnPropertyChangedCore(change);
+        }
+
+        private void TransitionsCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
+        {
+            if (!_transitionsEnabled)
+            {
+                return;
+            }
+
+            switch (e.Action)
+            {
+                case NotifyCollectionChangedAction.Add:
+                    AddTransitions(e.NewItems);
+                    break;
+                case NotifyCollectionChangedAction.Remove:
+                    RemoveTransitions(e.OldItems);
+                    break;
+                case NotifyCollectionChangedAction.Replace:
+                    RemoveTransitions(e.OldItems);
+                    AddTransitions(e.NewItems);
+                    break;
+                case NotifyCollectionChangedAction.Reset:
+                    throw new NotSupportedException("Transitions collection cannot be reset.");
             }
         }
 
-        protected override void OnPropertyChanged<T>(
+        private void AddTransitions(IList items)
-            AvaloniaProperty<T> property,
-            Optional<T> oldValue,
-            BindingValue<T> newValue,
-            BindingPriority priority)
         {
-            if (_transitions is null || _previousTransitions is null || priority == BindingPriority.Animation)
+            if (!_transitionsEnabled)
+            {
                 return;
+            }
+
+            _transitionState ??= new Dictionary<ITransition, TransitionState>();
 
-            // PERF-SENSITIVE: Called on every property change. Don't use LINQ here (too many allocations).
+            for (var i = 0; i < items.Count; ++i)
-            foreach (var transition in _transitions)
             {
-                if (transition.Property == property)
+                var t = (ITransition)items[i];
+
+                _transitionState.Add(t, new TransitionState
                 {
-                    if (_previousTransitions.TryGetValue(property, out var dispose))
+                    BaseValue = GetAnimationBaseValue(t.Property),
-                        dispose.Dispose();
+                });
+            }
+        }
 
-                    var instance = transition.Apply(
+        private void RemoveTransitions(IList items)
-                        this,
+        {
-                        Clock ?? Avalonia.Animation.Clock.GlobalClock,
+            if (_transitionState is null)
-                        oldValue.GetValueOrDefault(),
+            {
-                        newValue.GetValueOrDefault());
+                return;
+            }
 
-                    _previousTransitions[property] = instance;
+            for (var i = 0; i < items.Count; ++i)
-                    return;
+            {
+                var t = (ITransition)items[i];
+
+                if (_transitionState.TryGetValue(t, out var state))
+                {
+                    state.Instance?.Dispose();
+                    _transitionState.Remove(t);
                 }
             }
         }
+
+        private object GetAnimationBaseValue(AvaloniaProperty property)
+        {
+            var value = this.GetBaseValue(property, BindingPriority.LocalValue);
+
+            if (value == AvaloniaProperty.UnsetValue)
+            {
+                value = GetValue(property);
+            }
+
+            return value;
+        }
+
+        private class TransitionState
+        {
+            public IDisposable? Instance { get; set; }
+            public object? BaseValue { get; set; }
+        }
     }
 }

src/Avalonia.Animation/TransitionInstance.cs

@@ -19,6 +19,8 @@ namespace Avalonia.Animation
 
         public TransitionInstance(IClock clock, TimeSpan Duration)
         {
+            clock = clock ?? throw new ArgumentNullException(nameof(clock));
+
             _duration = Duration;
             _baseClock = clock;
         }

src/Avalonia.Animation/Transitions.cs

@@ -1,4 +1,6 @@
+using System;
 using Avalonia.Collections;
+using Avalonia.Threading;
 
 namespace Avalonia.Animation
 {
@@ -13,6 +15,17 @@ namespace Avalonia.Animation
         public Transitions()
         {
             ResetBehavior = ResetBehavior.Remove;
+            Validate = ValidateTransition;
+        }
+
+        private void ValidateTransition(ITransition obj)
+        {
+            Dispatcher.UIThread.VerifyAccess();
+
+            if (obj.Property.IsDirect)
+            {
+                throw new InvalidOperationException("Cannot animate a direct property.");
+            }
         }
     }
 }

src/Avalonia.Base/AvaloniaObject.cs

@@ -259,6 +259,21 @@ namespace Avalonia
             return registered.InvokeGetter(this);
         }
 
+        /// <inheritdoc/>
+        public Optional<T> GetBaseValue<T>(StyledPropertyBase<T> property, BindingPriority maxPriority)
+        {
+            property = property ?? throw new ArgumentNullException(nameof(property));
+            VerifyAccess();
+
+            if (_values is object &&
+                _values.TryGetValue(property, maxPriority, out var value))
+            {
+                return value;
+            }
+
+            return default;
+        }
+
         /// <summary>
         /// Checks whether a <see cref="AvaloniaProperty"/> is animating.
         /// </summary>
@@ -458,29 +473,43 @@ namespace Avalonia
             return _propertyChanged?.GetInvocationList();
         }
 
-        void IValueSink.ValueChanged<T>(
+        void IValueSink.ValueChanged<T>(AvaloniaPropertyChangedEventArgs<T> change)
-            StyledPropertyBase<T> property,
-            BindingPriority priority,
-            Optional<T> oldValue,
-            BindingValue<T> newValue)
         {
-            oldValue = oldValue.HasValue ? oldValue : GetInheritedOrDefault(property);
+            var property = (StyledPropertyBase<T>)change.Property;
-            newValue = newValue.HasValue ? newValue : newValue.WithValue(GetInheritedOrDefault(property));
 
-            LogIfError(property, newValue);
+            LogIfError(property, change.NewValue);
 
-            if (!EqualityComparer<T>.Default.Equals(oldValue.Value, newValue.Value))
+            // If the change is to the effective value of the property and no old/new value is set
+            // then fill in the old/new value from property inheritance/default value. We don't do
+            // this for non-effective value changes because these are only needed for property
+            // transitions, where knowing e.g. that an inherited value is active at an arbitrary
+            // priority isn't of any use and would introduce overhead.
+            if (change.IsEffectiveValueChange && !change.OldValue.HasValue)
             {
-                RaisePropertyChanged(property, oldValue, newValue, priority);
+                change.SetOldValue(GetInheritedOrDefault<T>(property));
+            }
 
-                Logger.TryGet(LogEventLevel.Verbose)?.Log(
+            if (change.IsEffectiveValueChange && !change.NewValue.HasValue)
-                    LogArea.Property,
+            {
-                    this,
+                change.SetNewValue(GetInheritedOrDefault(property));
-                    "{Property} changed from {$Old} to {$Value} with priority {Priority}",
+            }
-                    property,
+
-                    oldValue,
+            if (!change.IsEffectiveValueChange ||
-                    newValue,
+                !EqualityComparer<T>.Default.Equals(change.OldValue.Value, change.NewValue.Value))
-                    (BindingPriority)priority);
+            {
+                RaisePropertyChanged(change);
+
+                if (change.IsEffectiveValueChange)
+                {
+                    Logger.TryGet(LogEventLevel.Verbose)?.Log(
+                        LogArea.Property,
+                        this,
+                        "{Property} changed from {$Old} to {$Value} with priority {Priority}",
+                        property,
+                        change.OldValue,
+                        change.NewValue,
+                        change.Priority);
+                }
             }
         }
 
@@ -489,7 +518,13 @@ namespace Avalonia
             IPriorityValueEntry entry,
             Optional<T> oldValue) 
         {
-            ((IValueSink)this).ValueChanged(property, BindingPriority.Unset, oldValue, default);
+            var change = new AvaloniaPropertyChangedEventArgs<T>(
+                this,
+                property,
+                oldValue,
+                default,
+                BindingPriority.Unset);
+            ((IValueSink)this).ValueChanged(change);
         }
 
         /// <summary>
@@ -575,15 +610,20 @@ namespace Avalonia
         /// <summary>
         /// Called when a avalonia property changes on the object.
         /// </summary>
-        /// <param name="property">The property whose value has changed.</param>
+        /// <param name="change">The property change details.</param>
-        /// <param name="oldValue">The old value of the property.</param>
+        protected virtual void OnPropertyChangedCore<T>(AvaloniaPropertyChangedEventArgs<T> change)
-        /// <param name="newValue">The new value of the property.</param>
+        {
-        /// <param name="priority">The priority of the new value.</param>
+            if (change.IsEffectiveValueChange)
-        protected virtual void OnPropertyChanged<T>(
+            {
-            AvaloniaProperty<T> property,
+                OnPropertyChanged(change);
-            Optional<T> oldValue,
+            }
-            BindingValue<T> newValue,
+        }
-            BindingPriority priority)
+
+        /// <summary>
+        /// Called when a avalonia property changes on the object.
+        /// </summary>
+        /// <param name="change">The property change details.</param>
+        protected virtual void OnPropertyChanged<T>(AvaloniaPropertyChangedEventArgs<T> change)
         {
         }
 
@@ -600,57 +640,12 @@ namespace Avalonia
             BindingValue<T> newValue,
             BindingPriority priority = BindingPriority.LocalValue)
         {
-            property = property ?? throw new ArgumentNullException(nameof(property));
+            RaisePropertyChanged(new AvaloniaPropertyChangedEventArgs<T>(
-
+                this,
-            VerifyAccess();
+                property,
-
+                oldValue,
-            property.Notifying?.Invoke(this, true);
+                newValue,
-
+                priority));
-            try
-            {
-                AvaloniaPropertyChangedEventArgs<T> e = null;
-                var hasChanged = property.HasChangedSubscriptions;
-
-                if (hasChanged || _propertyChanged != null)
-                {
-                    e = new AvaloniaPropertyChangedEventArgs<T>(
-                        this,
-                        property,
-                        oldValue,
-                        newValue,
-                        priority);
-                }
-
-                OnPropertyChanged(property, oldValue, newValue, priority);
-
-                if (hasChanged)
-                {
-                    property.NotifyChanged(e);
-                }
-
-                _propertyChanged?.Invoke(this, e);
-
-                if (_inpcChanged != null)
-                {
-                    var inpce = new PropertyChangedEventArgs(property.Name);
-                    _inpcChanged(this, inpce);
-                }
-
-                if (property.Inherits && _inheritanceChildren != null)
-                {
-                    foreach (var child in _inheritanceChildren)
-                    {
-                        child.InheritedPropertyChanged(
-                            property,
-                            oldValue,
-                            newValue.ToOptional());
-                    }
-                }
-            }
-            finally
-            {
-                property.Notifying?.Invoke(this, false);
-            }
         }
 
         /// <summary>
@@ -689,7 +684,9 @@ namespace Avalonia
             return property.GetDefaultValue(GetType());
         }
 
-        private T GetValueOrInheritedOrDefault<T>(StyledPropertyBase<T> property)
+        private T GetValueOrInheritedOrDefault<T>(
+            StyledPropertyBase<T> property,
+            BindingPriority maxPriority = BindingPriority.Animation)
         {
             var o = this;
             var inherits = property.Inherits;
@@ -699,7 +696,7 @@ namespace Avalonia
             {
                 var values = o._values;
 
-                if (values?.TryGetValue(property, out value) == true)
+                if (values?.TryGetValue(property, maxPriority, out value) == true)
                 {
                     return value;
                 }
@@ -715,6 +712,51 @@ namespace Avalonia
             return property.GetDefaultValue(GetType());
         }
 
+        protected internal void RaisePropertyChanged<T>(AvaloniaPropertyChangedEventArgs<T> change)
+        {
+            VerifyAccess();
+
+            if (change.IsEffectiveValueChange)
+            {
+                change.Property.Notifying?.Invoke(this, true);
+            }
+
+            try
+            {
+                OnPropertyChangedCore(change);
+
+                if (change.IsEffectiveValueChange)
+                {
+                    change.Property.NotifyChanged(change);
+                    _propertyChanged?.Invoke(this, change);
+
+                    if (_inpcChanged != null)
+                    {
+                        var inpce = new PropertyChangedEventArgs(change.Property.Name);
+                        _inpcChanged(this, inpce);
+                    }
+
+                    if (change.Property.Inherits && _inheritanceChildren != null)
+                    {
+                        foreach (var child in _inheritanceChildren)
+                        {
+                            child.InheritedPropertyChanged(
+                                change.Property,
+                                change.OldValue,
+                                change.NewValue.ToOptional());
+                        }
+                    }
+                }
+            }
+            finally
+            {
+                if (change.IsEffectiveValueChange)
+                {
+                    change.Property.Notifying?.Invoke(this, false);
+                }
+            }
+        }
+
         /// <summary>
         /// Sets the value of a direct property.
         /// </summary>

src/Avalonia.Base/AvaloniaObjectExtensions.cs

@@ -448,6 +448,65 @@ namespace Avalonia
             };
         }
 
+        /// <summary>
+        /// Gets an <see cref="AvaloniaProperty"/> base value.
+        /// </summary>
+        /// <param name="target">The object.</param>
+        /// <param name="property">The property.</param>
+        /// <param name="maxPriority">The maximum priority for the value.</param>
+        /// <remarks>
+        /// For styled properties, gets the value of the property if set on the object with a
+        /// priority equal or lower to <paramref name="maxPriority"/>, otherwise
+        /// <see cref="AvaloniaProperty.UnsetValue"/>. Note that this method does not return
+        /// property values that come from inherited or default values.
+        /// 
+        /// For direct properties returns <see cref="GetValue(IAvaloniaObject, AvaloniaProperty)"/>.
+        /// </remarks>
+        public static object GetBaseValue(
+            this IAvaloniaObject target,
+            AvaloniaProperty property,
+            BindingPriority maxPriority)
+        {
+            target = target ?? throw new ArgumentNullException(nameof(target));
+            property = property ?? throw new ArgumentNullException(nameof(property));
+
+            return property.RouteGetBaseValue(target, maxPriority);
+        }
+
+        /// <summary>
+        /// Gets an <see cref="AvaloniaProperty"/> base value.
+        /// </summary>
+        /// <param name="target">The object.</param>
+        /// <param name="property">The property.</param>
+        /// <param name="maxPriority">The maximum priority for the value.</param>
+        /// <remarks>
+        /// For styled properties, gets the value of the property if set on the object with a
+        /// priority equal or lower to <paramref name="maxPriority"/>, otherwise
+        /// <see cref="Optional{T}.Empty"/>. Note that this method does not return property values
+        /// that come from inherited or default values.
+        /// 
+        /// For direct properties returns
+        /// <see cref="IAvaloniaObject.GetValue{T}(DirectPropertyBase{T})"/>.
+        /// </remarks>
+        public static Optional<T> GetBaseValue<T>(
+            this IAvaloniaObject target,
+            AvaloniaProperty<T> property,
+            BindingPriority maxPriority)
+        {
+            target = target ?? throw new ArgumentNullException(nameof(target));
+            property = property ?? throw new ArgumentNullException(nameof(property));
+
+            target = target ?? throw new ArgumentNullException(nameof(target));
+            property = property ?? throw new ArgumentNullException(nameof(property));
+
+            return property switch
+            {
+                StyledPropertyBase<T> styled => target.GetBaseValue(styled, maxPriority),
+                DirectPropertyBase<T> direct => target.GetValue(direct),
+                _ => throw new NotSupportedException("Unsupported AvaloniaProperty type.")
+            };
+        }
+
         /// <summary>
         /// Sets a <see cref="AvaloniaProperty"/> value.
         /// </summary>

src/Avalonia.Base/AvaloniaProperty.cs

@@ -496,6 +496,13 @@ namespace Avalonia
         /// <param name="o">The object instance.</param>
         internal abstract object RouteGetValue(IAvaloniaObject o);
 
+        /// <summary>
+        /// Routes an untyped GetBaseValue call to a typed call.
+        /// </summary>
+        /// <param name="o">The object instance.</param>
+        /// <param name="maxPriority">The maximum priority for the value.</param>
+        internal abstract object RouteGetBaseValue(IAvaloniaObject o, BindingPriority maxPriority);
+
         /// <summary>
         /// Routes an untyped SetValue call to a typed call.
         /// </summary>

src/Avalonia.Base/AvaloniaPropertyChangedEventArgs.cs

@@ -16,6 +16,7 @@ namespace Avalonia
         {
             Sender = sender;
             Priority = priority;
+            IsEffectiveValueChange = true;
         }
 
         /// <summary>
@@ -35,19 +36,11 @@ namespace Avalonia
         /// <summary>
         /// Gets the old value of the property.
         /// </summary>
-        /// <value>
-        /// The old value of the property or <see cref="AvaloniaProperty.UnsetValue"/> if the
-        /// property previously had no value.
-        /// </value>
         public object? OldValue => GetOldValue();
 
         /// <summary>
         /// Gets the new value of the property.
         /// </summary>
-        /// <value>
-        /// The new value of the property or <see cref="AvaloniaProperty.UnsetValue"/> if the
-        /// property previously had no value.
-        /// </value>
         public object? NewValue => GetNewValue();
 
         /// <summary>
@@ -58,6 +51,20 @@ namespace Avalonia
         /// </value>
         public BindingPriority Priority { get; private set; }
 
+        /// <summary>
+        /// Gets a value indicating whether the change represents a change to the effective value of
+        /// the property.
+        /// </summary>
+        /// <remarks>
+        /// This will usually be true, except in
+        /// <see cref="AvaloniaObject.OnPropertyChangedCore{T}(AvaloniaPropertyChangedEventArgs{T})"/>
+        /// which recieves notifications for all changes to property values, whether a value with a higher
+        /// priority is present or not. When this property is false, the change that is being signalled
+        /// has not resulted in a change to the property value on the object.
+        /// </remarks>
+        public bool IsEffectiveValueChange { get; private set; }
+
+        internal void MarkNonEffectiveValue() => IsEffectiveValueChange = false;
         protected abstract AvaloniaProperty GetProperty();
         protected abstract object? GetOldValue();
         protected abstract object? GetNewValue();

src/Avalonia.Base/AvaloniaPropertyChangedEventArgs`1.cs

@@ -1,4 +1,3 @@
-using System;
 using Avalonia.Data;
 
 #nullable enable
@@ -6,7 +5,7 @@ using Avalonia.Data;
 namespace Avalonia
 {
     /// <summary>
-    /// Provides information for a avalonia property change.
+    /// Provides information for an Avalonia property change.
     /// </summary>
     public class AvaloniaPropertyChangedEventArgs<T> : AvaloniaPropertyChangedEventArgs
     {
@@ -42,19 +41,28 @@ namespace Avalonia
         /// <summary>
         /// Gets the old value of the property.
         /// </summary>
-        /// <value>
+        /// <remarks>
-        /// The old value of the property.
+        /// When <see cref="AvaloniaPropertyChangedEventArgs.IsEffectiveValueChange"/> is true, returns the
-        /// </value>
+        /// old value of the property on the object. 
+        /// When <see cref="AvaloniaPropertyChangedEventArgs.IsEffectiveValueChange"/> is false, returns
+        /// <see cref="Optional{T}.Empty"/>.
+        /// </remarks>
         public new Optional<T> OldValue { get; private set; }
 
         /// <summary>
         /// Gets the new value of the property.
         /// </summary>
-        /// <value>
+        /// <remarks>
-        /// The new value of the property.
+        /// When <see cref="AvaloniaPropertyChangedEventArgs.IsEffectiveValueChange"/> is true, returns the
-        /// </value>
+        /// value of the property on the object.
+        /// When <see cref="AvaloniaPropertyChangedEventArgs.IsEffectiveValueChange"/> is false returns the
+        /// changed value, or <see cref="Optional{T}.Empty"/> if the value was removed.
+        /// </remarks>
         public new BindingValue<T> NewValue { get; private set; }
 
+        internal void SetOldValue(Optional<T> value) => OldValue = value;
+        internal void SetNewValue(BindingValue<T> value) => NewValue = value;
+
         protected override AvaloniaProperty GetProperty() => Property;
 
         protected override object? GetOldValue() => OldValue.GetValueOrDefault(AvaloniaProperty.UnsetValue);

src/Avalonia.Base/Data/BindingValue.cs

@@ -348,8 +348,8 @@ namespace Avalonia.Data
 
             return new BindingValue<T>(
                 fallbackValue.HasValue ?
-                    BindingValueType.DataValidationError :
+                    BindingValueType.DataValidationErrorWithFallback :
-                    BindingValueType.DataValidationErrorWithFallback,
+                    BindingValueType.DataValidationError,
                 fallbackValue.HasValue ? fallbackValue.Value : default,
                 e);
         }

src/Avalonia.Base/Data/Converters/BoolConverters.cs

@@ -3,7 +3,7 @@ using System.Linq;
 namespace Avalonia.Data.Converters
 {
     /// <summary>
-    /// Provides a set of useful <see cref="IValueConverter"/>s for working with string values.
+    /// Provides a set of useful <see cref="IValueConverter"/>s for working with bool values.
     /// </summary>
     public static class BoolConverters
     {

src/Avalonia.Base/Data/Core/Plugins/InpcPropertyAccessorPlugin.cs

@@ -1,7 +1,5 @@
 using System;
 using System.ComponentModel;
-using System.Linq;
-using System.Reactive.Linq;
 using System.Reflection;
 using Avalonia.Utilities;
 
@@ -14,7 +12,7 @@ namespace Avalonia.Data.Core.Plugins
     public class InpcPropertyAccessorPlugin : IPropertyAccessorPlugin
     {
         /// <inheritdoc/>
-        public bool Match(object obj, string propertyName) => true;
+        public bool Match(object obj, string propertyName) => GetPropertyWithName(obj.GetType(), propertyName) != null;
 
         /// <summary>
         /// Starts monitoring the value of a property on an object.
@@ -31,7 +29,8 @@ namespace Avalonia.Data.Core.Plugins
             Contract.Requires<ArgumentNullException>(propertyName != null);
 
             reference.TryGetTarget(out object instance);
-            var p = instance.GetType().GetRuntimeProperties().FirstOrDefault(x => x.Name == propertyName);
+
+            var p = GetPropertyWithName(instance.GetType(), propertyName);
 
             if (p != null)
             {
@@ -45,6 +44,14 @@ namespace Avalonia.Data.Core.Plugins
             }
         }
 
+        private static PropertyInfo GetPropertyWithName(Type type, string propertyName)
+        {
+            const BindingFlags bindingFlags = BindingFlags.NonPublic | BindingFlags.Public |
+                                              BindingFlags.Static | BindingFlags.Instance;
+
+            return type.GetProperty(propertyName, bindingFlags);
+        }
+
         private class Accessor : PropertyAccessorBase, IWeakSubscriber<PropertyChangedEventArgs>
         {
             private readonly WeakReference<object> _reference;

src/Avalonia.Base/Data/Core/Plugins/MethodAccessorPlugin.cs

@@ -1,13 +1,16 @@
 using System;
-using System.Linq;
+using System.Collections.Generic;
+using System.Linq.Expressions;
 using System.Reflection;
 
 namespace Avalonia.Data.Core.Plugins
 {
-    class MethodAccessorPlugin : IPropertyAccessorPlugin
+    public class MethodAccessorPlugin : IPropertyAccessorPlugin
     {
-        public bool Match(object obj, string methodName)
+        private readonly Dictionary<(Type, string), MethodInfo> _methodLookup =
-            => obj.GetType().GetRuntimeMethods().Any(x => x.Name == methodName);
+            new Dictionary<(Type, string), MethodInfo>();
+
+        public bool Match(object obj, string methodName) => GetFirstMethodWithName(obj.GetType(), methodName) != null;
 
         public IPropertyAccessor Start(WeakReference<object> reference, string methodName)
         {
@@ -15,17 +18,22 @@ namespace Avalonia.Data.Core.Plugins
             Contract.Requires<ArgumentNullException>(methodName != null);
 
             reference.TryGetTarget(out object instance);
-            var method = instance.GetType().GetRuntimeMethods().FirstOrDefault(x => x.Name == methodName);
+
+            var method = GetFirstMethodWithName(instance.GetType(), methodName);
 
             if (method != null)
             {
-                if (method.GetParameters().Length + (method.ReturnType == typeof(void) ? 0 : 1) > 8)
+                var parameters = method.GetParameters();
+
+                if (parameters.Length + (method.ReturnType == typeof(void) ? 0 : 1) > 8)
                 {
-                    var exception = new ArgumentException("Cannot create a binding accessor for a method with more than 8 parameters or more than 7 parameters if it has a non-void return type.", nameof(methodName));
+                    var exception = new ArgumentException(
+                        "Cannot create a binding accessor for a method with more than 8 parameters or more than 7 parameters if it has a non-void return type.",
+                        nameof(methodName));
                     return new PropertyError(new BindingNotification(exception, BindingErrorType.Error));
                 }
 
-                return new Accessor(reference, method);
+                return new Accessor(reference, method, parameters);
             }
             else
             {
@@ -35,31 +43,72 @@ namespace Avalonia.Data.Core.Plugins
             }
         }
 
+        private MethodInfo GetFirstMethodWithName(Type type, string methodName)
+        {
+            var key = (type, methodName);
+
+            if (!_methodLookup.TryGetValue(key, out MethodInfo methodInfo))
+            {
+                methodInfo = TryFindAndCacheMethod(type, methodName);
+            }
+
+            return methodInfo;
+        }
+
+        private MethodInfo TryFindAndCacheMethod(Type type, string methodName)
+        {
+            MethodInfo found = null;
+
+            const BindingFlags bindingFlags =
+                BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Static | BindingFlags.Instance;
+
+            var methods = type.GetMethods(bindingFlags);
+
+            foreach (MethodInfo methodInfo in methods)
+            {
+                if (methodInfo.Name == methodName)
+                {
+                    found = methodInfo;
+
+                    break;
+                }
+            }
+
+            _methodLookup.Add((type, methodName), found);
+
+            return found;
+        }
+
         private sealed class Accessor : PropertyAccessorBase
         {
-            public Accessor(WeakReference<object> reference, MethodInfo method)
+            public Accessor(WeakReference<object> reference, MethodInfo method, ParameterInfo[] parameters)
             {
                 Contract.Requires<ArgumentNullException>(reference != null);
                 Contract.Requires<ArgumentNullException>(method != null);
 
-                var paramTypes = method.GetParameters().Select(param => param.ParameterType).ToArray();
                 var returnType = method.ReturnType;
-                
+                bool hasReturn = returnType != typeof(void);
-                if (returnType == typeof(void))
+
+                var signatureTypeCount = (hasReturn ? 1 : 0) + parameters.Length;
+
+                var paramTypes = new Type[signatureTypeCount];
+
+                for (var i = 0; i < parameters.Length; i++)
                 {
-                    if (paramTypes.Length == 0)
+                    ParameterInfo parameter = parameters[i];
-                    {
+
-                        PropertyType = typeof(Action);
+                    paramTypes[i] = parameter.ParameterType;
-                    }
+                }
-                    else
+
-                    {
+                if (hasReturn)
-                        PropertyType = Type.GetType($"System.Action`{paramTypes.Length}").MakeGenericType(paramTypes); 
+                {
-                    }
+                    paramTypes[paramTypes.Length - 1] = returnType;
+
+                    PropertyType = Expression.GetFuncType(paramTypes);
                 }
                 else
                 {
-                    var genericTypeParameters = paramTypes.Concat(new[] { returnType }).ToArray();
+                    PropertyType = Expression.GetActionType(paramTypes);
-                    PropertyType = Type.GetType($"System.Func`{genericTypeParameters.Length}").MakeGenericType(genericTypeParameters);
                 }
 
                 if (method.IsStatic)

src/Avalonia.Base/Data/Core/PropertyAccessorNode.cs

@@ -62,8 +62,13 @@ namespace Avalonia.Data.Core
 
             if (accessor == null)
             {
-                throw new NotSupportedException(
+                reference.TryGetTarget(out object instance);
-                    $"Could not find a matching property accessor for {PropertyName}.");
+
+                var message = $"Could not find a matching property accessor for '{PropertyName}' on '{instance}'";
+
+                var exception = new MissingMemberException(message);
+
+                accessor = new PropertyError(new BindingNotification(exception, BindingErrorType.Error));
             }
 
             _accessor = accessor;

src/Avalonia.Base/DirectPropertyBase.cs

@@ -120,6 +120,11 @@ namespace Avalonia
             return o.GetValue<TValue>(this);
         }
 
+        internal override object RouteGetBaseValue(IAvaloniaObject o, BindingPriority maxPriority)
+        {
+            return o.GetValue<TValue>(this);
+        }
+
         /// <inheritdoc/>
         internal override IDisposable? RouteSetValue(
             IAvaloniaObject o,

src/Avalonia.Base/IAvaloniaObject.cs

@@ -41,6 +41,19 @@ namespace Avalonia
         /// <returns>The value.</returns>
         T GetValue<T>(DirectPropertyBase<T> property);
 
+        /// <summary>
+        /// Gets an <see cref="AvaloniaProperty"/> base value.
+        /// </summary>
+        /// <typeparam name="T">The type of the property.</typeparam>
+        /// <param name="property">The property.</param>
+        /// <param name="maxPriority">The maximum priority for the value.</param>
+        /// <remarks>
+        /// Gets the value of the property, if set on this object with a priority equal or lower to
+        /// <paramref name="maxPriority"/>, otherwise <see cref="Optional{T}.Empty"/>. Note that
+        /// this method does not return property values that come from inherited or default values.
+        /// </remarks>
+        Optional<T> GetBaseValue<T>(StyledPropertyBase<T> property, BindingPriority maxPriority);
+
         /// <summary>
         /// Checks whether a <see cref="AvaloniaProperty"/> is animating.
         /// </summary>

src/Avalonia.Base/Properties/AssemblyInfo.cs

@@ -7,4 +7,5 @@ using Avalonia.Metadata;
 [assembly: XmlnsDefinition("https://github.com/avaloniaui", "Avalonia.Data.Converters")]
 [assembly: InternalsVisibleTo("Avalonia.Base.UnitTests")]
 [assembly: InternalsVisibleTo("Avalonia.UnitTests")]
-[assembly: InternalsVisibleTo("DynamicProxyGenAssembly2")] 
+[assembly: InternalsVisibleTo("DynamicProxyGenAssembly2")]
+[assembly: InternalsVisibleTo("Avalonia.Controls.DataGrid")]

src/Avalonia.Base/PropertyStore/BindingEntry.cs

@@ -22,6 +22,7 @@ namespace Avalonia.PropertyStore
         private readonly IAvaloniaObject _owner;
         private IValueSink _sink;
         private IDisposable? _subscription;
+        private Optional<T> _value;
 
         public BindingEntry(
             IAvaloniaObject owner,
@@ -40,18 +41,21 @@ namespace Avalonia.PropertyStore
         public StyledPropertyBase<T> Property { get; }
         public BindingPriority Priority { get; }
         public IObservable<BindingValue<T>> Source { get; }
-        public Optional<T> Value { get; private set; }
+        Optional<object> IValue.GetValue() => _value.ToObject();
-        Optional<object> IValue.Value => Value.ToObject();
+
-        BindingPriority IValue.ValuePriority => Priority;
+        public Optional<T> GetValue(BindingPriority maxPriority)
+        {
+            return Priority >= maxPriority ? _value : Optional<T>.Empty;
+        }
 
         public void Dispose()
         {
             _subscription?.Dispose();
             _subscription = null;
-            _sink.Completed(Property, this, Value);
+            _sink.Completed(Property, this, _value);
         }
 
-        public void OnCompleted() => _sink.Completed(Property, this, Value);
+        public void OnCompleted() => _sink.Completed(Property, this, _value);
 
         public void OnError(Exception error)
         {
@@ -94,14 +98,14 @@ namespace Avalonia.PropertyStore
                 return;
             }
 
-            var old = Value;
+            var old = _value;
 
             if (value.Type != BindingValueType.DataValidationError)
             {
-                Value = value.ToOptional();
+                _value = value.ToOptional();
             }
 
-            _sink.ValueChanged(Property, Priority, old, value);
+            _sink.ValueChanged(new AvaloniaPropertyChangedEventArgs<T>(_owner, Property, old, value, Priority));
         }
     }
 }

src/Avalonia.Base/PropertyStore/ConstantValueEntry.cs

@@ -13,6 +13,7 @@ namespace Avalonia.PropertyStore
     internal class ConstantValueEntry<T> : IPriorityValueEntry<T>, IDisposable
     {
         private IValueSink _sink;
+        private Optional<T> _value;
 
         public ConstantValueEntry(
             StyledPropertyBase<T> property,
@@ -21,18 +22,21 @@ namespace Avalonia.PropertyStore
             IValueSink sink)
         {
             Property = property;
-            Value = value;
+            _value = value;
             Priority = priority;
             _sink = sink;
         }
 
         public StyledPropertyBase<T> Property { get; }
         public BindingPriority Priority { get; }
-        public Optional<T> Value { get; }
+        Optional<object> IValue.GetValue() => _value.ToObject();
-        Optional<object> IValue.Value => Value.ToObject();
-        BindingPriority IValue.ValuePriority => Priority;
 
-        public void Dispose() => _sink.Completed(Property, this, Value);
+        public Optional<T> GetValue(BindingPriority maxPriority = BindingPriority.Animation)
+        {
+            return Priority >= maxPriority ? _value : Optional<T>.Empty;
+        }
+
+        public void Dispose() => _sink.Completed(Property, this, _value);
         public void Reparent(IValueSink sink) => _sink = sink;
     }
 }

src/Avalonia.Base/PropertyStore/IValue.cs

@@ -9,8 +9,8 @@ namespace Avalonia.PropertyStore
     /// </summary>
     internal interface IValue
     {
-        Optional<object> Value { get; }
+        Optional<object> GetValue();
-        BindingPriority ValuePriority { get; }
+        BindingPriority Priority { get; }
     }
 
     /// <summary>
@@ -19,6 +19,6 @@ namespace Avalonia.PropertyStore
     /// <typeparam name="T">The property type.</typeparam>
     internal interface IValue<T> : IValue
     {
-        new Optional<T> Value { get; }
+        Optional<T> GetValue(BindingPriority maxPriority = BindingPriority.Animation);
     }
 }

src/Avalonia.Base/PropertyStore/IValueSink.cs

@@ -9,11 +9,7 @@ namespace Avalonia.PropertyStore
     /// </summary>
     internal interface IValueSink
     {
-        void ValueChanged<T>(
+        void ValueChanged<T>(AvaloniaPropertyChangedEventArgs<T> change);
-            StyledPropertyBase<T> property,
-            BindingPriority priority,
-            Optional<T> oldValue,
-            BindingValue<T> newValue);
 
         void Completed<T>(
             StyledPropertyBase<T> property,

src/Avalonia.Base/PropertyStore/LocalValueEntry.cs

@@ -14,9 +14,14 @@ namespace Avalonia.PropertyStore
         private T _value;
 
         public LocalValueEntry(T value) => _value = value;
-        public Optional<T> Value => _value;
+        public BindingPriority Priority => BindingPriority.LocalValue;
-        public BindingPriority ValuePriority => BindingPriority.LocalValue;
+        Optional<object> IValue.GetValue() => new Optional<object>(_value);
-        Optional<object> IValue.Value => Value.ToObject();
+        
+        public Optional<T> GetValue(BindingPriority maxPriority)
+        {
+            return BindingPriority.LocalValue >= maxPriority ? _value : Optional<T>.Empty;
+        }
+
         public void SetValue(T value) => _value = value;
     }
 }

src/Avalonia.Base/PropertyStore/PriorityValue.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.ComponentModel;
 using Avalonia.Data;
 
 #nullable enable
@@ -24,6 +25,7 @@ namespace Avalonia.PropertyStore
         private readonly List<IPriorityValueEntry<T>> _entries = new List<IPriorityValueEntry<T>>();
         private readonly Func<IAvaloniaObject, T, T>? _coerceValue;
         private Optional<T> _localValue;
+        private Optional<T> _value;
 
         public PriorityValue(
             IAvaloniaObject owner,
@@ -50,11 +52,13 @@ namespace Avalonia.PropertyStore
         {
             existing.Reparent(this);
             _entries.Add(existing);
+
+            var v = existing.GetValue();
             
-            if (existing.Value.HasValue)
+            if (v.HasValue)
             {
-                Value = existing.Value;
+                _value = v;
-                ValuePriority = existing.Priority;
+                Priority = existing.Priority;
             }
         }
 
@@ -65,18 +69,39 @@ namespace Avalonia.PropertyStore
             LocalValueEntry<T> existing)
             : this(owner, property, sink)
         {
-            _localValue = existing.Value;
+            _value = _localValue = existing.GetValue(BindingPriority.LocalValue);
-            Value = _localValue;
+            Priority = BindingPriority.LocalValue;
-            ValuePriority = BindingPriority.LocalValue;
         }
 
         public StyledPropertyBase<T> Property { get; }
-        public Optional<T> Value { get; private set; }
+        public BindingPriority Priority { get; private set; } = BindingPriority.Unset;
-        public BindingPriority ValuePriority { get; private set; }
         public IReadOnlyList<IPriorityValueEntry<T>> Entries => _entries;
-        Optional<object> IValue.Value => Value.ToObject();
+        Optional<object> IValue.GetValue() => _value.ToObject();
+
+        public void ClearLocalValue()
+        {
+            UpdateEffectiveValue(new AvaloniaPropertyChangedEventArgs<T>(
+                _owner,
+                Property,
+                default,
+                default,
+                BindingPriority.LocalValue));
+        }
+
+        public Optional<T> GetValue(BindingPriority maxPriority = BindingPriority.Animation)
+        {
+            if (Priority == BindingPriority.Unset)
+            {
+                return default;
+            }
 
-        public void ClearLocalValue() => UpdateEffectiveValue();
+            if (Priority >= maxPriority)
+            {
+                return _value;
+            }
+
+            return CalculateValue(maxPriority).Item1;
+        }
 
         public IDisposable? SetValue(T value, BindingPriority priority)
         {
@@ -94,7 +119,13 @@ namespace Avalonia.PropertyStore
                 result = entry;
             }
 
-            UpdateEffectiveValue();
+            UpdateEffectiveValue(new AvaloniaPropertyChangedEventArgs<T>(
+                _owner,
+                Property,
+                default,
+                value,
+                priority));
+
             return result;
         }
 
@@ -106,20 +137,19 @@ namespace Avalonia.PropertyStore
             return binding;
         }
 
-        public void CoerceValue() => UpdateEffectiveValue();
+        public void CoerceValue() => UpdateEffectiveValue(null);
 
-        void IValueSink.ValueChanged<TValue>(
+        void IValueSink.ValueChanged<TValue>(AvaloniaPropertyChangedEventArgs<TValue> change)
-            StyledPropertyBase<TValue> property,
-            BindingPriority priority,
-            Optional<TValue> oldValue,
-            BindingValue<TValue> newValue)
         {
-            if (priority == BindingPriority.LocalValue)
+            if (change.Priority == BindingPriority.LocalValue)
             {
                 _localValue = default;
             }
 
-            UpdateEffectiveValue();
+            if (change is AvaloniaPropertyChangedEventArgs<T> c)
+            {
+                UpdateEffectiveValue(c);
+            }
         }
 
         void IValueSink.Completed<TValue>(
@@ -128,7 +158,16 @@ namespace Avalonia.PropertyStore
             Optional<TValue> oldValue)
         {
             _entries.Remove((IPriorityValueEntry<T>)entry);
-            UpdateEffectiveValue();
+
+            if (oldValue is Optional<T> o)
+            {
+                UpdateEffectiveValue(new AvaloniaPropertyChangedEventArgs<T>(
+                    _owner,
+                    Property,
+                    o,
+                    default,
+                    entry.Priority));
+            }
         }
 
         private int FindInsertPoint(BindingPriority priority)
@@ -147,53 +186,73 @@ namespace Avalonia.PropertyStore
             return result;
         }
 
-        private void UpdateEffectiveValue()
+        public (Optional<T>, BindingPriority) CalculateValue(BindingPriority maxPriority)
         {
             var reachedLocalValues = false;
-            var value = default(Optional<T>);
 
-            if (_entries.Count > 0)
+            for (var i = _entries.Count - 1; i >= 0; --i)
             {
-                for (var i = _entries.Count - 1; i >= 0; --i)
+                var entry = _entries[i];
+
+                if (entry.Priority < maxPriority)
+                {
+                    continue;
+                }
+
+                if (!reachedLocalValues &&
+                    entry.Priority >= BindingPriority.LocalValue &&
+                    maxPriority <= BindingPriority.LocalValue &&
+                    _localValue.HasValue)
+                {
+                    return (_localValue, BindingPriority.LocalValue);
+                }
+
+                var entryValue = entry.GetValue();
+
+                if (entryValue.HasValue)
                 {
-                    var entry = _entries[i];
+                    return (entryValue, entry.Priority);
-
-                    if (!reachedLocalValues && entry.Priority >= BindingPriority.LocalValue)
-                    {
-                        reachedLocalValues = true;
-
-                        if (_localValue.HasValue)
-                        {
-                            value = _localValue;
-                            ValuePriority = BindingPriority.LocalValue;
-                            break;
-                        }
-                    }
-
-                    if (entry.Value.HasValue)
-                    {
-                        value = entry.Value;
-                        ValuePriority = entry.Priority;
-                        break;
-                    }
                 }
             }
-            else if (_localValue.HasValue)
+
+            if (!reachedLocalValues &&
+                maxPriority <= BindingPriority.LocalValue &&
+                _localValue.HasValue)
             {
-                value = _localValue;
+                return (_localValue, BindingPriority.LocalValue);
-                ValuePriority = BindingPriority.LocalValue;
             }
 
+            return (default, BindingPriority.Unset);
+        }
+
+        private void UpdateEffectiveValue(AvaloniaPropertyChangedEventArgs<T>? change)
+        {
+            var (value, priority) = CalculateValue(BindingPriority.Animation);
+
             if (value.HasValue && _coerceValue != null)
             {
                 value = _coerceValue(_owner, value.Value);
             }
 
-            if (value != Value)
+            Priority = priority;
+
+            if (value != _value)
+            {
+                var old = _value;
+                _value = value;
+
+                _sink.ValueChanged(new AvaloniaPropertyChangedEventArgs<T>(
+                    _owner,
+                    Property,
+                    old,
+                    value,
+                    Priority));
+            }
+            else if (change is object)
             {
-                var old = Value;
+                change.MarkNonEffectiveValue();
-                Value = value;
+                change.SetOldValue(default);
-                _sink.ValueChanged(Property, ValuePriority, old, value);
+                _sink.ValueChanged(change);
             }
         }
     }

src/Avalonia.Base/StyledPropertyBase.cs

@@ -197,6 +197,13 @@ namespace Avalonia
             return o.GetValue<TValue>(this);
         }
 
+        /// <inheritdoc/>
+        internal override object RouteGetBaseValue(IAvaloniaObject o, BindingPriority maxPriority)
+        {
+            var value = o.GetBaseValue<TValue>(this, maxPriority);
+            return value.HasValue ? value.Value : AvaloniaProperty.UnsetValue;
+        }
+
         /// <inheritdoc/>
         internal override IDisposable RouteSetValue(
             IAvaloniaObject o,

src/Avalonia.Base/Utilities/MathUtilities.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Runtime.InteropServices;
 
 namespace Avalonia.Utilities
 {
@@ -8,6 +7,11 @@ namespace Avalonia.Utilities
     /// </summary>
     public static class MathUtilities
     {
+        // smallest such that 1.0+DoubleEpsilon != 1.0
+        internal static readonly double DoubleEpsilon = 2.2204460492503131e-016;
+
+        private const float FloatEpsilon = 1.192092896e-07F;
+
         /// <summary>
         /// AreClose - Returns whether or not two doubles are "close".  That is, whether or 
         /// not they are within epsilon of each other.
@@ -18,11 +22,26 @@ namespace Avalonia.Utilities
         {
             //in case they are Infinities (then epsilon check does not work)
             if (value1 == value2) return true;
-            double eps = (Math.Abs(value1) + Math.Abs(value2) + 10.0) * double.Epsilon;
+            double eps = (Math.Abs(value1) + Math.Abs(value2) + 10.0) * DoubleEpsilon;
             double delta = value1 - value2;
             return (-eps < delta) && (eps > delta);
         }
 
+        /// <summary>
+        /// AreClose - Returns whether or not two floats are "close".  That is, whether or 
+        /// not they are within epsilon of each other.
+        /// </summary> 
+        /// <param name="value1"> The first float to compare. </param>
+        /// <param name="value2"> The second float to compare. </param>
+        public static bool AreClose(float value1, float value2)
+        {
+            //in case they are Infinities (then epsilon check does not work)
+            if (value1 == value2) return true;
+            float eps = (Math.Abs(value1) + Math.Abs(value2) + 10.0f) * FloatEpsilon;
+            float delta = value1 - value2;
+            return (-eps < delta) && (eps > delta);
+        }
+
         /// <summary>
         /// LessThan - Returns whether or not the first double is less than the second double.
         /// That is, whether or not the first is strictly less than *and* not within epsilon of
@@ -35,6 +54,18 @@ namespace Avalonia.Utilities
             return (value1 < value2) && !AreClose(value1, value2);
         }
 
+        /// <summary>
+        /// LessThan - Returns whether or not the first float is less than the second float.
+        /// That is, whether or not the first is strictly less than *and* not within epsilon of
+        /// the other number.
+        /// </summary>
+        /// <param name="value1"> The first single float to compare. </param>
+        /// <param name="value2"> The second single float to compare. </param>
+        public static bool LessThan(float value1, float value2)
+        {
+            return (value1 < value2) && !AreClose(value1, value2);
+        }
+
         /// <summary>
         /// GreaterThan - Returns whether or not the first double is greater than the second double.
         /// That is, whether or not the first is strictly greater than *and* not within epsilon of
@@ -47,6 +78,18 @@ namespace Avalonia.Utilities
             return (value1 > value2) && !AreClose(value1, value2);
         }
 
+        /// <summary>
+        /// GreaterThan - Returns whether or not the first float is greater than the second float.
+        /// That is, whether or not the first is strictly greater than *and* not within epsilon of
+        /// the other number.
+        /// </summary>
+        /// <param name="value1"> The first float to compare. </param>
+        /// <param name="value2"> The second float to compare. </param>
+        public static bool GreaterThan(float value1, float value2)
+        {
+            return (value1 > value2) && !AreClose(value1, value2);
+        }
+
         /// <summary>
         /// LessThanOrClose - Returns whether or not the first double is less than or close to
         /// the second double.  That is, whether or not the first is strictly less than or within
@@ -59,6 +102,18 @@ namespace Avalonia.Utilities
             return (value1 < value2) || AreClose(value1, value2);
         }
 
+        /// <summary>
+        /// LessThanOrClose - Returns whether or not the first float is less than or close to
+        /// the second float.  That is, whether or not the first is strictly less than or within
+        /// epsilon of the other number.
+        /// </summary>
+        /// <param name="value1"> The first float to compare. </param>
+        /// <param name="value2"> The second float to compare. </param>
+        public static bool LessThanOrClose(float value1, float value2)
+        {
+            return (value1 < value2) || AreClose(value1, value2);
+        }
+
         /// <summary>
         /// GreaterThanOrClose - Returns whether or not the first double is greater than or close to
         /// the second double.  That is, whether or not the first is strictly greater than or within
@@ -71,6 +126,18 @@ namespace Avalonia.Utilities
             return (value1 > value2) || AreClose(value1, value2);
         }
 
+        /// <summary>
+        /// GreaterThanOrClose - Returns whether or not the first float is greater than or close to
+        /// the second float.  That is, whether or not the first is strictly greater than or within
+        /// epsilon of the other number.
+        /// </summary>
+        /// <param name="value1"> The first float to compare. </param>
+        /// <param name="value2"> The second float to compare. </param>
+        public static bool GreaterThanOrClose(float value1, float value2)
+        {
+            return (value1 > value2) || AreClose(value1, value2);
+        }
+
         /// <summary>
         /// IsOne - Returns whether or not the double is "close" to 1.  Same as AreClose(double, 1),
         /// but this is faster.
@@ -78,7 +145,17 @@ namespace Avalonia.Utilities
         /// <param name="value"> The double to compare to 1. </param>
         public static bool IsOne(double value)
         {
-            return Math.Abs(value - 1.0) < 10.0 * double.Epsilon;
+            return Math.Abs(value - 1.0) < 10.0 * DoubleEpsilon;
+        }
+
+        /// <summary>
+        /// IsOne - Returns whether or not the float is "close" to 1.  Same as AreClose(float, 1),
+        /// but this is faster.
+        /// </summary>
+        /// <param name="value"> The float to compare to 1. </param>
+        public static bool IsOne(float value)
+        {
+            return Math.Abs(value - 1.0f) < 10.0f * FloatEpsilon;
         }
 
         /// <summary>
@@ -88,7 +165,17 @@ namespace Avalonia.Utilities
         /// <param name="value"> The double to compare to 0. </param>
         public static bool IsZero(double value)
         {
-            return Math.Abs(value) < 10.0 * double.Epsilon;
+            return Math.Abs(value) < 10.0 * DoubleEpsilon;
+        }
+
+        /// <summary>
+        /// IsZero - Returns whether or not the float is "close" to 0.  Same as AreClose(float, 0),
+        /// but this is faster.
+        /// </summary>
+        /// <param name="value"> The float to compare to 0. </param>
+        public static bool IsZero(float value)
+        {
+            return Math.Abs(value) < 10.0f * FloatEpsilon;
         }
 
         /// <summary>
@@ -100,6 +187,11 @@ namespace Avalonia.Utilities
         /// <returns>The clamped value.</returns>
         public static double Clamp(double val, double min, double max)
         {
+            if (min > max)
+            {
+                ThrowCannotBeGreaterThanException(min, max);
+            }
+
             if (val < min)
             {
                 return min;
@@ -128,7 +220,7 @@ namespace Avalonia.Utilities
             double newValue;
 
             // If DPI == 1, don't use DPI-aware rounding.
-            if (!MathUtilities.AreClose(dpiScale, 1.0))
+            if (!MathUtilities.IsOne(dpiScale))
             {
                 newValue = Math.Round(value * dpiScale) / dpiScale;
                 // If rounding produces a value unacceptable to layout (NaN, Infinity or MaxValue), use the original value.
@@ -158,7 +250,7 @@ namespace Avalonia.Utilities
         {
             if (min > max)
             {
-                throw new ArgumentException($"{min} cannot be greater than {max}.");
+                ThrowCannotBeGreaterThanException(min, max);
             }
 
             if (val < min)
@@ -174,5 +266,40 @@ namespace Avalonia.Utilities
                 return val;
             }
         }
+
+        /// <summary>
+        /// Converts an angle in degrees to radians.
+        /// </summary>
+        /// <param name="angle">The angle in degrees.</param>
+        /// <returns>The angle in radians.</returns>
+        public static double Deg2Rad(double angle)
+        {
+            return angle * (Math.PI / 180d);
+        }
+
+        /// <summary>
+        /// Converts an angle in gradians to radians.
+        /// </summary>
+        /// <param name="angle">The angle in gradians.</param>
+        /// <returns>The angle in radians.</returns>
+        public static double Grad2Rad(double angle)
+        {
+            return angle * (Math.PI / 200d);
+        }
+
+        /// <summary>
+        /// Converts an angle in turns to radians.
+        /// </summary>
+        /// <param name="angle">The angle in turns.</param>
+        /// <returns>The angle in radians.</returns>
+        public static double Turn2Rad(double angle)
+        {
+            return angle * 2 * Math.PI;
+        }
+        
+        private static void ThrowCannotBeGreaterThanException(double min, double max)
+        {
+            throw new ArgumentException($"{min} cannot be greater than {max}.");
+        }
     }
 }

src/Avalonia.Base/Utilities/TypeUtilities.cs

@@ -115,45 +115,46 @@ namespace Avalonia.Utilities
                 return true;
             }
 
+            var toUnderl = Nullable.GetUnderlyingType(to) ?? to;
             var from = value.GetType();
 
-            if (to.IsAssignableFrom(from))
+            if (toUnderl.IsAssignableFrom(from))
             {
                 result = value;
                 return true;
             }
 
-            if (to == typeof(string))
+            if (toUnderl == typeof(string))
             {
-                result = Convert.ToString(value);
+                result = Convert.ToString(value, culture);
                 return true;
             }
 
-            if (to.IsEnum && from == typeof(string))
+            if (toUnderl.IsEnum && from == typeof(string))
             {
-                if (Enum.IsDefined(to, (string)value))
+                if (Enum.IsDefined(toUnderl, (string)value))
                 {
-                    result = Enum.Parse(to, (string)value);
+                    result = Enum.Parse(toUnderl, (string)value);
                     return true;
                 }
             }
 
-            if (!from.IsEnum && to.IsEnum)
+            if (!from.IsEnum && toUnderl.IsEnum)
             {
                 result = null;
 
-                if (TryConvert(Enum.GetUnderlyingType(to), value, culture, out object enumValue))
+                if (TryConvert(Enum.GetUnderlyingType(toUnderl), value, culture, out object enumValue))
                 {
-                    result = Enum.ToObject(to, enumValue);
+                    result = Enum.ToObject(toUnderl, enumValue);
                     return true;
                 }
             }
 
-            if (from.IsEnum && IsNumeric(to))
+            if (from.IsEnum && IsNumeric(toUnderl))
             {
                 try
                 {
-                    result = Convert.ChangeType((int)value, to, culture);
+                    result = Convert.ChangeType((int)value, toUnderl, culture);
                     return true;
                 }
                 catch
@@ -164,7 +165,7 @@ namespace Avalonia.Utilities
             }
 
             var convertableFrom = Array.IndexOf(InbuiltTypes, from);
-            var convertableTo = Array.IndexOf(InbuiltTypes, to);
+            var convertableTo = Array.IndexOf(InbuiltTypes, toUnderl);
 
             if (convertableFrom != -1 && convertableTo != -1)
             {
@@ -172,7 +173,7 @@ namespace Avalonia.Utilities
                 {
                     try
                     {
-                        result = Convert.ChangeType(value, to, culture);
+                        result = Convert.ChangeType(value, toUnderl, culture);
                         return true;
                     }
                     catch
@@ -183,15 +184,23 @@ namespace Avalonia.Utilities
                 }
             }
 
-            var typeConverter = TypeDescriptor.GetConverter(to);
+            var toTypeConverter = TypeDescriptor.GetConverter(toUnderl);
+
+            if (toTypeConverter.CanConvertFrom(from) == true)
+            {
+                result = toTypeConverter.ConvertFrom(null, culture, value);
+                return true;
+            }
+
+            var fromTypeConverter = TypeDescriptor.GetConverter(from);
 
-            if (typeConverter.CanConvertFrom(from) == true)
+            if (fromTypeConverter.CanConvertTo(toUnderl) == true)
             {
-                result = typeConverter.ConvertFrom(null, culture, value);
+                result = fromTypeConverter.ConvertTo(null, culture, value, toUnderl);
                 return true;
             }
 
-            var cast = FindTypeConversionOperatorMethod(from, to, OperatorType.Implicit | OperatorType.Explicit);
+            var cast = FindTypeConversionOperatorMethod(from, toUnderl, OperatorType.Implicit | OperatorType.Explicit);
 
             if (cast != null)
             {

src/Avalonia.Base/ValueStore.cs

@@ -37,7 +37,7 @@ namespace Avalonia
         {
             if (_values.TryGetValue(property, out var slot))
             {
-                return slot.ValuePriority < BindingPriority.LocalValue;
+                return slot.Priority < BindingPriority.LocalValue;
             }
 
             return false;
@@ -47,21 +47,24 @@ namespace Avalonia
         {
             if (_values.TryGetValue(property, out var slot))
             {
-                return slot.Value.HasValue;
+                return slot.GetValue().HasValue;
             }
 
             return false;
         }
 
-        public bool TryGetValue<T>(StyledPropertyBase<T> property, out T value)
+        public bool TryGetValue<T>(
+            StyledPropertyBase<T> property,
+            BindingPriority maxPriority,
+            out T value)
         {
             if (_values.TryGetValue(property, out var slot))
             {
-                var v = (IValue<T>)slot;
+                var v = ((IValue<T>)slot).GetValue(maxPriority);
 
-                if (v.Value.HasValue)
+                if (v.HasValue)
                 {
-                    value = v.Value.Value;
+                    value = v.Value;
                     return true;
                 }
             }
@@ -90,17 +93,22 @@ namespace Avalonia
                 _values.AddValue(property, entry);
                 result = entry.SetValue(value, priority);
             }
-            else if (priority == BindingPriority.LocalValue)
-            {
-                _values.AddValue(property, new LocalValueEntry<T>(value));
-                _sink.ValueChanged(property, priority, default, value);
-            }
             else
             {
-                var entry = new ConstantValueEntry<T>(property, value, priority, this);
+                var change = new AvaloniaPropertyChangedEventArgs<T>(_owner, property, default, value, priority);
-                _values.AddValue(property, entry);
+
-                _sink.ValueChanged(property, priority, default, value);
+                if (priority == BindingPriority.LocalValue)
-                result = entry;
+                {
+                    _values.AddValue(property, new LocalValueEntry<T>(value));
+                    _sink.ValueChanged(change);
+                }
+                else
+                {
+                    var entry = new ConstantValueEntry<T>(property, value, priority, this);
+                    _values.AddValue(property, entry);
+                    _sink.ValueChanged(change);
+                    result = entry;
+                }
             }
 
             return result;
@@ -149,13 +157,14 @@ namespace Avalonia
 
                     if (remove)
                     {
-                        var old = TryGetValue(property, out var value) ? value : default;
+                        var old = TryGetValue(property, BindingPriority.LocalValue, out var value) ? value : default;
                         _values.Remove(property);
-                        _sink.ValueChanged(
+                        _sink.ValueChanged(new AvaloniaPropertyChangedEventArgs<T>(
+                            _owner,
                             property,
-                            BindingPriority.Unset,
                             old,
-                            BindingValue<T>.Unset);
+                            default,
+                            BindingPriority.Unset));
                     }
                 }
             }
@@ -176,23 +185,20 @@ namespace Avalonia
         {
             if (_values.TryGetValue(property, out var slot))
             {
+                var slotValue = slot.GetValue();
                 return new Diagnostics.AvaloniaPropertyValue(
                     property,
-                    slot.Value.HasValue ? slot.Value.Value : AvaloniaProperty.UnsetValue,
+                    slotValue.HasValue ? slotValue.Value : AvaloniaProperty.UnsetValue,
-                    slot.ValuePriority,
+                    slot.Priority,
                     null);
             }
 
             return null;
         }
 
-        void IValueSink.ValueChanged<T>(
+        void IValueSink.ValueChanged<T>(AvaloniaPropertyChangedEventArgs<T> change)
-            StyledPropertyBase<T> property,
-            BindingPriority priority,
-            Optional<T> oldValue,
-            BindingValue<T> newValue)
         {
-            _sink.ValueChanged(property, priority, oldValue, newValue);
+            _sink.ValueChanged(change);
         }
 
         void IValueSink.Completed<T>(
@@ -232,9 +238,14 @@ namespace Avalonia
             {
                 if (priority == BindingPriority.LocalValue)
                 {
-                    var old = l.Value;
+                    var old = l.GetValue(BindingPriority.LocalValue);
                     l.SetValue(value);
-                    _sink.ValueChanged(property, priority, old, value);
+                    _sink.ValueChanged(new AvaloniaPropertyChangedEventArgs<T>(
+                        _owner,
+                        property,
+                        old,
+                        value,
+                        priority));
                 }
                 else
                 {

src/Avalonia.Build.Tasks/CompileAvaloniaXamlTask.cs

@@ -12,6 +12,8 @@ namespace Avalonia.Build.Tasks
     {
         public bool Execute()
         {
+            Enum.TryParse(ReportImportance, true, out MessageImportance outputImportance);
+
             OutputPath = OutputPath ?? AssemblyFile;
             var outputPdb = GetPdbPath(OutputPath);
             var input = AssemblyFile;
@@ -32,9 +34,12 @@ namespace Avalonia.Build.Tasks
                 }
             }
 
+            var msg = $"CompileAvaloniaXamlTask -> AssemblyFile:{AssemblyFile}, ProjectDirectory:{ProjectDirectory}, OutputPath:{OutputPath}";
+            BuildEngine.LogMessage(msg, outputImportance < MessageImportance.Low ? MessageImportance.High : outputImportance);
+
             var res = XamlCompilerTaskExecutor.Compile(BuildEngine, input,
                 File.ReadAllLines(ReferencesFilePath).Where(l => !string.IsNullOrWhiteSpace(l)).ToArray(),
-                ProjectDirectory, OutputPath, VerifyIl);
+                ProjectDirectory, OutputPath, VerifyIl, outputImportance);
             if (!res.Success)
                 return false;
             if (!res.WrittenFile)
@@ -68,7 +73,9 @@ namespace Avalonia.Build.Tasks
         public string OutputPath { get; set; }
 
         public bool VerifyIl { get; set; }
-        
+
+        public string ReportImportance { get; set; }
+
         public IBuildEngine BuildEngine { get; set; }
         public ITaskHost HostObject { get; set; }
     }

src/Avalonia.Build.Tasks/Extensions.cs

@@ -9,14 +9,19 @@ namespace Avalonia.Build.Tasks
 
         public static void LogError(this IBuildEngine engine, BuildEngineErrorCode code, string file, string message)
         {
-            engine.LogErrorEvent(new BuildErrorEventArgs("Avalonia", FormatErrorCode(code), file ?? "", 0, 0, 0, 0, message, 
+            engine.LogErrorEvent(new BuildErrorEventArgs("Avalonia", FormatErrorCode(code), file ?? "", 0, 0, 0, 0, message,
                 "", "Avalonia"));
         }
-        
+
         public static void LogWarning(this IBuildEngine engine, BuildEngineErrorCode code, string file, string message)
         {
             engine.LogWarningEvent(new BuildWarningEventArgs("Avalonia", FormatErrorCode(code), file ?? "", 0, 0, 0, 0, message,
                 "", "Avalonia"));
         }
+
+        public static void LogMessage(this IBuildEngine engine, string message, MessageImportance imp)
+        {
+            engine.LogMessageEvent(new BuildMessageEventArgs(message, "", "Avalonia", imp));
+        }
     }
 }

src/Avalonia.Build.Tasks/GenerateAvaloniaResourcesTask.cs

@@ -22,6 +22,10 @@ namespace Avalonia.Build.Tasks
         [Required]
         public ITaskItem[] EmbeddedResources { get; set; }
 
+        public string ReportImportance { get; set; }
+
+        private MessageImportance _reportImportance;
+
         class Source
         {
             public string Path { get; set; }
@@ -29,15 +33,11 @@ namespace Avalonia.Build.Tasks
             private byte[] _data;
             private string _sourcePath;
 
-            public Source(string file, string root)
+            public Source(string relativePath, string root)
             {
-                file = SPath.GetFullPath(file);
                 root = SPath.GetFullPath(root);
-                var fileUri = new Uri(file, UriKind.Absolute);
+                Path = "/" + relativePath.Replace('\\', '/');
-                var rootUri = new Uri(root, UriKind.Absolute);
+                _sourcePath = SPath.Combine(root, relativePath);
-                rootUri = new Uri(rootUri.ToString().TrimEnd('/') + '/');
-                Path = '/' + rootUri.MakeRelativeUri(fileUri).ToString().TrimStart('/');
-                _sourcePath = file;
                 Size = (int)new FileInfo(_sourcePath).Length;
             }
 
@@ -65,7 +65,14 @@ namespace Avalonia.Build.Tasks
             }
         }
 
-        List<Source> BuildResourceSources() => Resources.Select(r => new Source(r.ItemSpec, Root)).ToList();
+        List<Source> BuildResourceSources()
+           => Resources.Select(r =>
+           {
+              
+               var src = new Source(r.ItemSpec, Root);
+               BuildEngine.LogMessage($"avares -> name:{src.Path}, path: {src.SystemPath}, size:{src.Size}, ItemSpec:{r.ItemSpec}", _reportImportance);
+               return src;
+           }).ToList();
 
         private void Pack(Stream output, List<Source> sources)
         {
@@ -136,10 +143,14 @@ namespace Avalonia.Build.Tasks
             sources.Add(new Source("/!AvaloniaResourceXamlInfo", ms.ToArray()));
             return true;
         }
-        
+
         public bool Execute()
         {
-            foreach(var r in EmbeddedResources.Where(r=>r.ItemSpec.EndsWith(".xaml")||r.ItemSpec.EndsWith(".paml")))
+            Enum.TryParse<MessageImportance>(ReportImportance, out _reportImportance);
+
+            BuildEngine.LogMessage($"GenerateAvaloniaResourcesTask -> Root: {Root}, {Resources?.Count()} resources, Output:{Output}", _reportImportance < MessageImportance.Low ? MessageImportance.High : _reportImportance);
+
+            foreach (var r in EmbeddedResources.Where(r => r.ItemSpec.EndsWith(".xaml") || r.ItemSpec.EndsWith(".paml")))
                 BuildEngine.LogWarning(BuildEngineErrorCode.LegacyResmScheme, r.ItemSpec,
                     "XAML file is packed using legacy EmbeddedResource/resm scheme, relative URIs won't work");
             var resources = BuildResourceSources();

src/Avalonia.Build.Tasks/XamlCompilerTaskExecutor.cs

@@ -40,7 +40,7 @@ namespace Avalonia.Build.Tasks
         }
         
         public static CompileResult Compile(IBuildEngine engine, string input, string[] references, string projectDirectory,
-            string output, bool verifyIl)
+            string output, bool verifyIl, MessageImportance logImportance)
         {
             var typeSystem = new CecilTypeSystem(references.Concat(new[] {input}), input);
             var asm = typeSystem.TargetAssemblyDefinition;
@@ -121,6 +121,8 @@ namespace Avalonia.Build.Tasks
                 {
                     try
                     {
+                        engine.LogMessage($"XAMLIL: {res.Name} -> {res.Uri}", logImportance);
+
                         // StreamReader is needed here to handle BOM
                         var xaml = new StreamReader(new MemoryStream(res.FileContents)).ReadToEnd();
                         var parsed = XDocumentXamlIlParser.Parse(xaml);

src/Avalonia.Controls.DataGrid/DataGrid.cs

@@ -1,5 +1,4 @@
-// (c) Copyright Microsoft Corporation.
+// This source is subject to the Microsoft Public License (Ms-PL).
-// This source is subject to the Microsoft Public License (Ms-PL).
 // Please see http://go.microsoft.com/fwlink/?LinkID=131993 for details.
 // All other rights reserved. 
 
@@ -767,7 +766,7 @@ namespace Avalonia.Controls
         /// <summary>
         /// ItemsProperty property changed handler.
         /// </summary>
-        /// <param name="e">AvaloniaPropertyChangedEventArgs.</param>
+        /// <param name="e">The event arguments.</param>
         private void OnItemsPropertyChanged(AvaloniaPropertyChangedEventArgs e)
         {
             if (!_areHandlersSuspended)
@@ -2682,7 +2681,7 @@ namespace Avalonia.Controls
             {
                 return;
             }
-            Debug.Assert(DoubleUtil.LessThanOrClose(_vScrollBar.Value, _vScrollBar.Maximum));
+            Debug.Assert(MathUtilities.LessThanOrClose(_vScrollBar.Value, _vScrollBar.Maximum));
 
             _verticalScrollChangesIgnored++;
             try
@@ -2699,7 +2698,7 @@ namespace Avalonia.Controls
                 }
                 else if (scrollEventType == ScrollEventType.SmallDecrement)
                 {
-                    if (DoubleUtil.GreaterThan(NegVerticalOffset, 0))
+                    if (MathUtilities.GreaterThan(NegVerticalOffset, 0))
                     {
                         DisplayData.PendingVerticalScrollHeight -= NegVerticalOffset;
                     }
@@ -2718,7 +2717,7 @@ namespace Avalonia.Controls
                     DisplayData.PendingVerticalScrollHeight = _vScrollBar.Value - _verticalOffset;
                 }
 
-                if (!DoubleUtil.IsZero(DisplayData.PendingVerticalScrollHeight))
+                if (!MathUtilities.IsZero(DisplayData.PendingVerticalScrollHeight))
                 {
                     // Invalidate so the scroll happens on idle
                     InvalidateRowsMeasure(invalidateIndividualElements: false);
@@ -3347,22 +3346,22 @@ namespace Avalonia.Controls
                 bool needHorizScrollbarWithoutVertScrollbar = false;
 
                 if (allowHorizScrollbar &&
-                    DoubleUtil.GreaterThan(totalVisibleWidth, cellsWidth) &&
+                    MathUtilities.GreaterThan(totalVisibleWidth, cellsWidth) &&
-                    DoubleUtil.LessThan(totalVisibleFrozenWidth, cellsWidth) &&
+                    MathUtilities.LessThan(totalVisibleFrozenWidth, cellsWidth) &&
-                    DoubleUtil.LessThanOrClose(horizScrollBarHeight, cellsHeight))
+                    MathUtilities.LessThanOrClose(horizScrollBarHeight, cellsHeight))
                 {
                     double oldDataHeight = cellsHeight;
                     cellsHeight -= horizScrollBarHeight;
                     Debug.Assert(cellsHeight >= 0);
                     needHorizScrollbarWithoutVertScrollbar = needHorizScrollbar = true;
-                    if (allowVertScrollbar && (DoubleUtil.LessThanOrClose(totalVisibleWidth - cellsWidth, vertScrollBarWidth) ||
+                    if (allowVertScrollbar && (MathUtilities.LessThanOrClose(totalVisibleWidth - cellsWidth, vertScrollBarWidth) ||
-                        DoubleUtil.LessThanOrClose(cellsWidth - totalVisibleFrozenWidth, vertScrollBarWidth)))
+                        MathUtilities.LessThanOrClose(cellsWidth - totalVisibleFrozenWidth, vertScrollBarWidth)))
                     {
                         // Would we still need a horizontal scrollbar without the vertical one?
                         UpdateDisplayedRows(DisplayData.FirstScrollingSlot, cellsHeight);
                         if (DisplayData.NumTotallyDisplayedScrollingElements != VisibleSlotCount)
                         {
-                            needHorizScrollbar = DoubleUtil.LessThan(totalVisibleFrozenWidth, cellsWidth - vertScrollBarWidth);
+                            needHorizScrollbar = MathUtilities.LessThan(totalVisibleFrozenWidth, cellsWidth - vertScrollBarWidth);
                         }
                     }
 
@@ -3375,8 +3374,8 @@ namespace Avalonia.Controls
 
                 UpdateDisplayedRows(DisplayData.FirstScrollingSlot, cellsHeight);
                 if (allowVertScrollbar &&
-                    DoubleUtil.GreaterThan(cellsHeight, 0) &&
+                    MathUtilities.GreaterThan(cellsHeight, 0) &&
-                    DoubleUtil.LessThanOrClose(vertScrollBarWidth, cellsWidth) &&
+                    MathUtilities.LessThanOrClose(vertScrollBarWidth, cellsWidth) &&
                     DisplayData.NumTotallyDisplayedScrollingElements != VisibleSlotCount)
                 {
                     cellsWidth -= vertScrollBarWidth;
@@ -3390,9 +3389,9 @@ namespace Avalonia.Controls
 
                 if (allowHorizScrollbar &&
                     needVertScrollbar && !needHorizScrollbar &&
-                    DoubleUtil.GreaterThan(totalVisibleWidth, cellsWidth) &&
+                    MathUtilities.GreaterThan(totalVisibleWidth, cellsWidth) &&
-                    DoubleUtil.LessThan(totalVisibleFrozenWidth, cellsWidth) &&
+                    MathUtilities.LessThan(totalVisibleFrozenWidth, cellsWidth) &&
-                    DoubleUtil.LessThanOrClose(horizScrollBarHeight, cellsHeight))
+                    MathUtilities.LessThanOrClose(horizScrollBarHeight, cellsHeight))
                 {
                     cellsWidth += vertScrollBarWidth;
                     cellsHeight -= horizScrollBarHeight;
@@ -3423,7 +3422,7 @@ namespace Avalonia.Controls
                 if (allowVertScrollbar)
                 {
                     if (cellsHeight > 0 &&
-                        DoubleUtil.LessThanOrClose(vertScrollBarWidth, cellsWidth) &&
+                        MathUtilities.LessThanOrClose(vertScrollBarWidth, cellsWidth) &&
                         DisplayData.NumTotallyDisplayedScrollingElements != VisibleSlotCount)
                     {
                         cellsWidth -= vertScrollBarWidth;
@@ -3440,9 +3439,9 @@ namespace Avalonia.Controls
                 if (allowHorizScrollbar)
                 {
                     if (cellsWidth > 0 &&
-                        DoubleUtil.LessThanOrClose(horizScrollBarHeight, cellsHeight) &&
+                        MathUtilities.LessThanOrClose(horizScrollBarHeight, cellsHeight) &&
-                        DoubleUtil.GreaterThan(totalVisibleWidth, cellsWidth) &&
+                        MathUtilities.GreaterThan(totalVisibleWidth, cellsWidth) &&
-                        DoubleUtil.LessThan(totalVisibleFrozenWidth, cellsWidth))
+                        MathUtilities.LessThan(totalVisibleFrozenWidth, cellsWidth))
                     {
                         cellsHeight -= horizScrollBarHeight;
                         Debug.Assert(cellsHeight >= 0);
@@ -5388,7 +5387,7 @@ namespace Avalonia.Controls
         private void SetVerticalOffset(double newVerticalOffset)
         {
             _verticalOffset = newVerticalOffset;
-            if (_vScrollBar != null && !DoubleUtil.AreClose(newVerticalOffset, _vScrollBar.Value))
+            if (_vScrollBar != null && !MathUtilities.AreClose(newVerticalOffset, _vScrollBar.Value))
             {
                 _vScrollBar.Value = _verticalOffset;
             }

src/Avalonia.Controls.DataGrid/DataGridColumnHeader.cs

@@ -301,7 +301,7 @@ namespace Avalonia.Controls
         private static bool CanResizeColumn(DataGridColumn column)
         {
             if (column.OwningGrid != null && column.OwningGrid.ColumnsInternal != null && column.OwningGrid.UsesStarSizing &&
-                (column.OwningGrid.ColumnsInternal.LastVisibleColumn == column || !DoubleUtil.AreClose(column.OwningGrid.ColumnsInternal.VisibleEdgedColumnsWidth, column.OwningGrid.CellsWidth)))
+                (column.OwningGrid.ColumnsInternal.LastVisibleColumn == column || !MathUtilities.AreClose(column.OwningGrid.ColumnsInternal.VisibleEdgedColumnsWidth, column.OwningGrid.CellsWidth)))
             {
                 return false;
             }

src/Avalonia.Controls.DataGrid/DataGridColumns.cs

@@ -44,7 +44,7 @@ namespace Avalonia.Controls
         /// <returns>The remaining amount of adjustment.</returns>
         internal double AdjustColumnWidths(int displayIndex, double amount, bool userInitiated)
         {
-            if (!DoubleUtil.IsZero(amount))
+            if (!MathUtilities.IsZero(amount))
             {
                 if (amount < 0)
                 {
@@ -777,7 +777,7 @@ namespace Avalonia.Controls
         private double AdjustStarColumnWidths(int displayIndex, double adjustment, bool userInitiated)
         {
             double remainingAdjustment = adjustment;
-            if (DoubleUtil.IsZero(remainingAdjustment))
+            if (MathUtilities.IsZero(remainingAdjustment))
             {
                 return remainingAdjustment;
             }
@@ -843,7 +843,7 @@ namespace Avalonia.Controls
         /// <returns>The remaining amount of adjustment.</returns>
         private double AdjustStarColumnWidths(int displayIndex, double remainingAdjustment, bool userInitiated, Func<DataGridColumn, double> targetWidth)
         {
-            if (DoubleUtil.IsZero(remainingAdjustment))
+            if (MathUtilities.IsZero(remainingAdjustment))
             {
                 return remainingAdjustment;
             }
@@ -1244,7 +1244,7 @@ namespace Avalonia.Controls
             Debug.Assert(amount < 0);
             Debug.Assert(column.Width.UnitType != DataGridLengthUnitType.Star);
 
-            if (DoubleUtil.GreaterThanOrClose(targetWidth, column.Width.DisplayValue))
+            if (MathUtilities.GreaterThanOrClose(targetWidth, column.Width.DisplayValue))
             {
                 return amount;
             }
@@ -1271,7 +1271,7 @@ namespace Avalonia.Controls
         /// <returns>The remaining amount of adjustment.</returns>
         private double DecreaseNonStarColumnWidths(int displayIndex, Func<DataGridColumn, double> targetWidth, double amount, bool reverse, bool affectNewColumns)
         {
-            if (DoubleUtil.GreaterThanOrClose(amount, 0))
+            if (MathUtilities.GreaterThanOrClose(amount, 0))
             {
                 return amount;
             }
@@ -1285,7 +1285,7 @@ namespace Avalonia.Controls
                     (affectNewColumns || column.IsInitialDesiredWidthDetermined)))
             {
                 amount = DecreaseNonStarColumnWidth(column, Math.Max(column.ActualMinWidth, targetWidth(column)), amount);
-                if (DoubleUtil.IsZero(amount))
+                if (MathUtilities.IsZero(amount))
                 {
                     break;
                 }
@@ -1392,7 +1392,7 @@ namespace Avalonia.Controls
         /// <returns>The remaining amount of adjustment.</returns>
         private double IncreaseNonStarColumnWidths(int displayIndex, Func<DataGridColumn, double> targetWidth, double amount, bool reverse, bool affectNewColumns)
         {
-            if (DoubleUtil.LessThanOrClose(amount, 0))
+            if (MathUtilities.LessThanOrClose(amount, 0))
             {
                 return amount;
             }
@@ -1406,7 +1406,7 @@ namespace Avalonia.Controls
                     (affectNewColumns || column.IsInitialDesiredWidthDetermined)))
             {
                 amount = IncreaseNonStarColumnWidth(column, Math.Min(column.ActualMaxWidth, targetWidth(column)), amount);
-                if (DoubleUtil.IsZero(amount))
+                if (MathUtilities.IsZero(amount))
                 {
                     break;
                 }

src/Avalonia.Controls.DataGrid/DataGridLength.cs

@@ -529,7 +529,7 @@ namespace Avalonia.Controls
                     //  in this case drop value part and print only "Star"
                     case DataGridLengthUnitType.Star:
                         return (
-                            DoubleUtil.AreClose(1.0, dataGridLength.Value.Value)
+                            MathUtilities.AreClose(1.0, dataGridLength.Value.Value)
                             ? _starSuffix
                             : Convert.ToString(dataGridLength.Value.Value, culture ?? CultureInfo.CurrentCulture) + DataGridLengthConverter._starSuffix);
 

src/Avalonia.Controls.DataGrid/DataGridRow.cs

@@ -879,7 +879,7 @@ namespace Avalonia.Controls
                 && (double.IsNaN(_detailsContent.Height))
                 && (AreDetailsVisible)
                 && (!double.IsNaN(_detailsDesiredHeight))
-                && !DoubleUtil.AreClose(_detailsContent.Bounds.Inflate(_detailsContent.Margin).Height, _detailsDesiredHeight)
+                && !MathUtilities.AreClose(_detailsContent.Bounds.Inflate(_detailsContent.Margin).Height, _detailsDesiredHeight)
                 && Slot != -1)
             {
                 _detailsDesiredHeight = _detailsContent.Bounds.Inflate(_detailsContent.Margin).Height;

src/Avalonia.Controls.DataGrid/DataGridRows.cs

@@ -329,7 +329,7 @@ namespace Avalonia.Controls
 
         internal void OnRowsMeasure()
         {
-            if (!DoubleUtil.IsZero(DisplayData.PendingVerticalScrollHeight))
+            if (!MathUtilities.IsZero(DisplayData.PendingVerticalScrollHeight))
             {
                 ScrollSlotsByHeight(DisplayData.PendingVerticalScrollHeight);
                 DisplayData.PendingVerticalScrollHeight = 0;
@@ -432,7 +432,7 @@ namespace Avalonia.Controls
             }
             else if (DisplayData.FirstScrollingSlot == slot && slot != -1)
             {
-                if (!DoubleUtil.IsZero(NegVerticalOffset))
+                if (!MathUtilities.IsZero(NegVerticalOffset))
                 {
                     // First displayed row is partially scrolled of. Let's scroll it so that NegVerticalOffset becomes 0.
                     DisplayData.PendingVerticalScrollHeight = -NegVerticalOffset;
@@ -447,7 +447,7 @@ namespace Avalonia.Controls
             {
                 // Scroll up to the new row so it becomes the first displayed row
                 firstFullSlot = DisplayData.FirstScrollingSlot - 1;
-                if (DoubleUtil.GreaterThan(NegVerticalOffset, 0))
+                if (MathUtilities.GreaterThan(NegVerticalOffset, 0))
                 {
                     deltaY = -NegVerticalOffset;
                 }
@@ -470,7 +470,7 @@ namespace Avalonia.Controls
                 // Figure out how much of the last row is cut off
                 double rowHeight = GetExactSlotElementHeight(DisplayData.LastScrollingSlot);
                 double availableHeight = AvailableSlotElementRoom + rowHeight;
-                if (DoubleUtil.AreClose(rowHeight, availableHeight))
+                if (MathUtilities.AreClose(rowHeight, availableHeight))
                 {
                     if (DisplayData.LastScrollingSlot == slot)
                     {
@@ -499,7 +499,7 @@ namespace Avalonia.Controls
                 {
                     ResetDisplayedRows();
                 }
-                if (DoubleUtil.GreaterThanOrClose(GetExactSlotElementHeight(slot), CellsHeight))
+                if (MathUtilities.GreaterThanOrClose(GetExactSlotElementHeight(slot), CellsHeight))
                 {
                     // The entire row won't fit in the DataGrid so we start showing it from the top
                     NegVerticalOffset = 0;
@@ -519,7 +519,7 @@ namespace Avalonia.Controls
             }
 
             // 
-            Debug.Assert(DoubleUtil.LessThanOrClose(NegVerticalOffset, _verticalOffset));
+            Debug.Assert(MathUtilities.LessThanOrClose(NegVerticalOffset, _verticalOffset));
 
             SetVerticalOffset(_verticalOffset);
 
@@ -1660,7 +1660,7 @@ namespace Avalonia.Controls
         private void ScrollSlotsByHeight(double height)
         {
             Debug.Assert(DisplayData.FirstScrollingSlot >= 0);
-            Debug.Assert(!DoubleUtil.IsZero(height));
+            Debug.Assert(!MathUtilities.IsZero(height));
 
             _scrollingByHeight = true;
             try
@@ -1672,7 +1672,7 @@ namespace Avalonia.Controls
                 {
                     // Scrolling Down
                     int lastVisibleSlot = GetPreviousVisibleSlot(SlotCount);
-                    if (_vScrollBar != null && DoubleUtil.AreClose(_vScrollBar.Maximum, newVerticalOffset))
+                    if (_vScrollBar != null && MathUtilities.AreClose(_vScrollBar.Maximum, newVerticalOffset))
                     {
                         // We've scrolled to the bottom of the ScrollBar, automatically place the user at the very bottom
                         // of the DataGrid.  If this produces very odd behavior, evaluate the coping strategy used by
@@ -1684,7 +1684,7 @@ namespace Avalonia.Controls
                     else
                     {
                         deltaY = GetSlotElementHeight(newFirstScrollingSlot) - NegVerticalOffset;
-                        if (DoubleUtil.LessThan(height, deltaY))
+                        if (MathUtilities.LessThan(height, deltaY))
                         {
                             // We've merely covered up more of the same row we're on
                             NegVerticalOffset += height;
@@ -1707,7 +1707,7 @@ namespace Avalonia.Controls
                             }
                             else
                             {
-                                while (DoubleUtil.LessThanOrClose(deltaY, height))
+                                while (MathUtilities.LessThanOrClose(deltaY, height))
                                 {
                                     if (newFirstScrollingSlot < lastVisibleSlot)
                                     {
@@ -1727,7 +1727,7 @@ namespace Avalonia.Controls
 
                                     double rowHeight = GetExactSlotElementHeight(newFirstScrollingSlot);
                                     double remainingHeight = height - deltaY;
-                                    if (DoubleUtil.LessThanOrClose(rowHeight, remainingHeight))
+                                    if (MathUtilities.LessThanOrClose(rowHeight, remainingHeight))
                                     {
                                         deltaY += rowHeight;
                                     }
@@ -1744,7 +1744,7 @@ namespace Avalonia.Controls
                 else
                 {
                     // Scrolling Up
-                    if (DoubleUtil.GreaterThanOrClose(height + NegVerticalOffset, 0))
+                    if (MathUtilities.GreaterThanOrClose(height + NegVerticalOffset, 0))
                     {
                         // We've merely exposing more of the row we're on
                         NegVerticalOffset += height;
@@ -1778,7 +1778,7 @@ namespace Avalonia.Controls
                         else
                         {
                             int lastScrollingSlot = DisplayData.LastScrollingSlot;
-                            while (DoubleUtil.GreaterThan(deltaY, height))
+                            while (MathUtilities.GreaterThan(deltaY, height))
                             {
                                 if (newFirstScrollingSlot > 0)
                                 {
@@ -1797,7 +1797,7 @@ namespace Avalonia.Controls
                                 }
                                 double rowHeight = GetExactSlotElementHeight(newFirstScrollingSlot);
                                 double remainingHeight = height - deltaY;
-                                if (DoubleUtil.LessThanOrClose(rowHeight + remainingHeight, 0))
+                                if (MathUtilities.LessThanOrClose(rowHeight + remainingHeight, 0))
                                 {
                                     deltaY -= rowHeight;
                                 }
@@ -1809,7 +1809,7 @@ namespace Avalonia.Controls
                             }
                         }
                     }
-                    if (DoubleUtil.GreaterThanOrClose(0, newVerticalOffset) && newFirstScrollingSlot != 0)
+                    if (MathUtilities.GreaterThanOrClose(0, newVerticalOffset) && newFirstScrollingSlot != 0)
                     {
                         // We've scrolled to the top of the ScrollBar, automatically place the user at the very top
                         // of the DataGrid.  If this produces very odd behavior, evaluate the RowHeight estimate.  
@@ -1822,7 +1822,7 @@ namespace Avalonia.Controls
                 }
 
                 double firstRowHeight = GetExactSlotElementHeight(newFirstScrollingSlot);
-                if (DoubleUtil.LessThan(firstRowHeight, NegVerticalOffset))
+                if (MathUtilities.LessThan(firstRowHeight, NegVerticalOffset))
                 {
                     // We've scrolled off more of the first row than what's possible.  This can happen
                     // if the first row got shorter (Ex: Collpasing RowDetails) or if the user has a recycling
@@ -1838,11 +1838,11 @@ namespace Avalonia.Controls
                 UpdateDisplayedRows(newFirstScrollingSlot, CellsHeight);
 
                 double firstElementHeight = GetExactSlotElementHeight(DisplayData.FirstScrollingSlot);
-                if (DoubleUtil.GreaterThan(NegVerticalOffset, firstElementHeight))
+                if (MathUtilities.GreaterThan(NegVerticalOffset, firstElementHeight))
                 {
                     int firstElementSlot = DisplayData.FirstScrollingSlot;
                     // We filled in some rows at the top and now we have a NegVerticalOffset that's greater than the first element
-                    while (newFirstScrollingSlot > 0 && DoubleUtil.GreaterThan(NegVerticalOffset, firstElementHeight))
+                    while (newFirstScrollingSlot > 0 && MathUtilities.GreaterThan(NegVerticalOffset, firstElementHeight))
                     {
                         int previousSlot = GetPreviousVisibleSlot(firstElementSlot);
                         if (previousSlot == -1)
@@ -1872,7 +1872,7 @@ namespace Avalonia.Controls
                 {
                     _verticalOffset = NegVerticalOffset;
                 }
-                else if (DoubleUtil.GreaterThan(NegVerticalOffset, newVerticalOffset))
+                else if (MathUtilities.GreaterThan(NegVerticalOffset, newVerticalOffset))
                 {
                     // The scrolled-in row was larger than anticipated. Adjust the DataGrid so the ScrollBar thumb
                     // can stay in the same place
@@ -1890,8 +1890,8 @@ namespace Avalonia.Controls
 
                 DisplayData.FullyRecycleElements();
 
-                Debug.Assert(DoubleUtil.GreaterThanOrClose(NegVerticalOffset, 0));
+                Debug.Assert(MathUtilities.GreaterThanOrClose(NegVerticalOffset, 0));
-                Debug.Assert(DoubleUtil.GreaterThanOrClose(_verticalOffset, NegVerticalOffset));
+                Debug.Assert(MathUtilities.GreaterThanOrClose(_verticalOffset, NegVerticalOffset));
             }
             finally
             {
@@ -2032,7 +2032,7 @@ namespace Avalonia.Controls
             double deltaY = -NegVerticalOffset;
             int visibleScrollingRows = 0;
 
-            if (DoubleUtil.LessThanOrClose(displayHeight, 0) || SlotCount == 0 || ColumnsItemsInternal.Count == 0)
+            if (MathUtilities.LessThanOrClose(displayHeight, 0) || SlotCount == 0 || ColumnsItemsInternal.Count == 0)
             {
                 return;
             }
@@ -2044,7 +2044,7 @@ namespace Avalonia.Controls
             }
 
             int slot = firstDisplayedScrollingSlot;
-            while (slot < SlotCount && !DoubleUtil.GreaterThanOrClose(deltaY, displayHeight))
+            while (slot < SlotCount && !MathUtilities.GreaterThanOrClose(deltaY, displayHeight))
             {
                 deltaY += GetExactSlotElementHeight(slot);
                 visibleScrollingRows++;
@@ -2052,7 +2052,7 @@ namespace Avalonia.Controls
                 slot = GetNextVisibleSlot(slot);
             }
 
-            while (DoubleUtil.LessThan(deltaY, displayHeight) && slot >= 0)
+            while (MathUtilities.LessThan(deltaY, displayHeight) && slot >= 0)
             {
                 slot = GetPreviousVisibleSlot(firstDisplayedScrollingSlot);
                 if (slot >= 0)
@@ -2063,14 +2063,14 @@ namespace Avalonia.Controls
                 }
             }
             // If we're up to the first row, and we still have room left, uncover as much of the first row as we can
-            if (firstDisplayedScrollingSlot == 0 && DoubleUtil.LessThan(deltaY, displayHeight))
+            if (firstDisplayedScrollingSlot == 0 && MathUtilities.LessThan(deltaY, displayHeight))
             {
                 double newNegVerticalOffset = Math.Max(0, NegVerticalOffset - displayHeight + deltaY);
                 deltaY += NegVerticalOffset - newNegVerticalOffset;
                 NegVerticalOffset = newNegVerticalOffset;
             }
 
-            if (DoubleUtil.GreaterThan(deltaY, displayHeight) || (DoubleUtil.AreClose(deltaY, displayHeight) && DoubleUtil.GreaterThan(NegVerticalOffset, 0)))
+            if (MathUtilities.GreaterThan(deltaY, displayHeight) || (MathUtilities.AreClose(deltaY, displayHeight) && MathUtilities.GreaterThan(NegVerticalOffset, 0)))
             {
                 DisplayData.NumTotallyDisplayedScrollingElements = visibleScrollingRows - 1;
             }
@@ -2108,7 +2108,7 @@ namespace Avalonia.Controls
             double deltaY = 0;
             int visibleScrollingRows = 0;
 
-            if (DoubleUtil.LessThanOrClose(displayHeight, 0) || SlotCount == 0 || ColumnsItemsInternal.Count == 0)
+            if (MathUtilities.LessThanOrClose(displayHeight, 0) || SlotCount == 0 || ColumnsItemsInternal.Count == 0)
             {
                 ResetDisplayedRows();
                 return;
@@ -2120,7 +2120,7 @@ namespace Avalonia.Controls
             }
 
             int slot = lastDisplayedScrollingRow;
-            while (DoubleUtil.LessThan(deltaY, displayHeight) && slot >= 0)
+            while (MathUtilities.LessThan(deltaY, displayHeight) && slot >= 0)
             {
                 deltaY += GetExactSlotElementHeight(slot);
                 visibleScrollingRows++;
@@ -2542,7 +2542,7 @@ namespace Avalonia.Controls
                             double heightChange = UpdateRowGroupVisibility(rowGroupInfo, isVisible, isDisplayed: false);
                             // Use epsilon instead of 0 here so that in the off chance that our estimates put the vertical offset negative
                             // the user can still scroll to the top since the offset is non-zero
-                            SetVerticalOffset(Math.Max(DoubleUtil.DBL_EPSILON, _verticalOffset + heightChange));
+                            SetVerticalOffset(Math.Max(MathUtilities.DoubleEpsilon, _verticalOffset + heightChange));
                         }
                         else
                         {
@@ -3024,4 +3024,4 @@ namespace Avalonia.Controls
         }
 #endif
     }
-}
+}

src/Avalonia.Controls.DataGrid/Primitives/DataGridCellsPresenter.cs

@@ -310,9 +310,9 @@ namespace Avalonia.Controls.Primitives
             double leftEdge = column.IsFrozen ? frozenLeftEdge : scrollingLeftEdge;
             double rightEdge = leftEdge + column.ActualWidth;
             return 
-                DoubleUtil.GreaterThan(rightEdge, 0) &&
+                MathUtilities.GreaterThan(rightEdge, 0) &&
-                DoubleUtil.LessThanOrClose(leftEdge, OwningGrid.CellsWidth) &&
+                MathUtilities.LessThanOrClose(leftEdge, OwningGrid.CellsWidth) &&
-                DoubleUtil.GreaterThan(rightEdge, frozenLeftEdge); // scrolling column covered up by frozen column(s)
+                MathUtilities.GreaterThan(rightEdge, frozenLeftEdge); // scrolling column covered up by frozen column(s)
         }
     }
 }

src/Avalonia.Controls.DataGrid/Utils/DoubleUtil.cs

@@ -1,136 +0,0 @@
-// (c) Copyright Microsoft Corporation.
-// This source is subject to the Microsoft Public License (Ms-PL).
-// Please see http://go.microsoft.com/fwlink/?LinkID=131993 for details.
-// All other rights reserved.
-
-using System;
-
-namespace Avalonia.Controls.Utils
-{
-    internal static class DoubleUtil
-    {
-        internal const double DBL_EPSILON = 1e-6;
-
-        /// <summary>
-        /// AreClose - Returns whether or not two doubles are "close".  That is, whether or 
-        /// not they are within epsilon of each other.  Note that this epsilon is proportional
-        /// to the numbers themselves to that AreClose survives scalar multiplication.
-        /// There are plenty of ways for this to return false even for numbers which
-        /// are theoretically identical, so no code calling this should fail to work if this 
-        /// returns false.  This is important enough to repeat:
-        /// NB: NO CODE CALLING THIS FUNCTION SHOULD DEPEND ON ACCURATE RESULTS - this should be
-        /// used for optimizations *only*.
-        /// </summary>
-        /// <returns>
-        /// bool - the result of the AreClose comparison.
-        /// </returns>
-        /// <param name="value1"> The first double to compare. </param>
-        /// <param name="value2"> The second double to compare. </param>
-        public static bool AreClose(double value1, double value2)
-        {
-            //in case they are Infinities (then epsilon check does not work)
-            if (value1 == value2) return true;
-            // This computes (|value1-value2| / (|value1| + |value2| + 10.0)) < DBL_EPSILON
-            double eps = (Math.Abs(value1) + Math.Abs(value2) + 10.0) * DBL_EPSILON;
-            double delta = value1 - value2;
-            return (-eps < delta) && (eps > delta);
-        }
-
-        /// <summary>
-        /// GreaterThan - Returns whether or not the first double is greater than the second double.
-        /// That is, whether or not the first is strictly greater than *and* not within epsilon of
-        /// the other number.  Note that this epsilon is proportional to the numbers themselves
-        /// to that AreClose survives scalar multiplication.  Note,
-        /// There are plenty of ways for this to return false even for numbers which
-        /// are theoretically identical, so no code calling this should fail to work if this 
-        /// returns false.  This is important enough to repeat:
-        /// NB: NO CODE CALLING THIS FUNCTION SHOULD DEPEND ON ACCURATE RESULTS - this should be
-        /// used for optimizations *only*.
-        /// </summary>
-        /// <returns>
-        /// bool - the result of the GreaterThan comparison.
-        /// </returns>
-        /// <param name="value1"> The first double to compare. </param>
-        /// <param name="value2"> The second double to compare. </param>
-        public static bool GreaterThan(double value1, double value2)
-        {
-            return (value1 > value2) && !AreClose(value1, value2);
-        }
-
-        /// <summary>
-        /// GreaterThanOrClose - Returns whether or not the first double is greater than or close to
-        /// the second double.  That is, whether or not the first is strictly greater than or within
-        /// epsilon of the other number.  Note that this epsilon is proportional to the numbers 
-        /// themselves to that AreClose survives scalar multiplication.  Note,
-        /// There are plenty of ways for this to return false even for numbers which
-        /// are theoretically identical, so no code calling this should fail to work if this 
-        /// returns false.  This is important enough to repeat:
-        /// NB: NO CODE CALLING THIS FUNCTION SHOULD DEPEND ON ACCURATE RESULTS - this should be
-        /// used for optimizations *only*.
-        /// </summary>
-        /// <returns>
-        /// bool - the result of the GreaterThanOrClose comparison.
-        /// </returns>
-        /// <param name="value1"> The first double to compare. </param>
-        /// <param name="value2"> The second double to compare. </param>
-        public static bool GreaterThanOrClose(double value1, double value2)
-        {
-            return (value1 > value2) || AreClose(value1, value2);
-        }
-
-        /// <summary>
-        /// IsZero - Returns whether or not the double is "close" to 0.  Same as AreClose(double, 0),
-        /// but this is faster.
-        /// </summary>
-        /// <returns>
-        /// bool - the result of the IsZero comparison.
-        /// </returns>
-        /// <param name="value"> The double to compare to 0. </param>
-        public static bool IsZero(double value)
-        {
-            return Math.Abs(value) < 10.0 * DBL_EPSILON;
-        }
-
-        /// <summary>
-        /// LessThan - Returns whether or not the first double is less than the second double.
-        /// That is, whether or not the first is strictly less than *and* not within epsilon of
-        /// the other number.  Note that this epsilon is proportional to the numbers themselves
-        /// to that AreClose survives scalar multiplication.  Note,
-        /// There are plenty of ways for this to return false even for numbers which
-        /// are theoretically identical, so no code calling this should fail to work if this 
-        /// returns false.  This is important enough to repeat:
-        /// NB: NO CODE CALLING THIS FUNCTION SHOULD DEPEND ON ACCURATE RESULTS - this should be
-        /// used for optimizations *only*.
-        /// </summary>
-        /// <returns>
-        /// bool - the result of the LessThan comparison.
-        /// </returns>
-        /// <param name="value1"> The first double to compare. </param>
-        /// <param name="value2"> The second double to compare. </param>
-        public static bool LessThan(double value1, double value2)
-        {
-            return (value1 < value2) && !AreClose(value1, value2);
-        }
-
-        /// <summary>
-        /// LessThanOrClose - Returns whether or not the first double is less than or close to
-        /// the second double.  That is, whether or not the first is strictly less than or within
-        /// epsilon of the other number.  Note that this epsilon is proportional to the numbers 
-        /// themselves to that AreClose survives scalar multiplication.  Note,
-        /// There are plenty of ways for this to return false even for numbers which
-        /// are theoretically identical, so no code calling this should fail to work if this 
-        /// returns false.  This is important enough to repeat:
-        /// NB: NO CODE CALLING THIS FUNCTION SHOULD DEPEND ON ACCURATE RESULTS - this should be
-        /// used for optimizations *only*.
-        /// </summary>
-        /// <returns>
-        /// bool - the result of the LessThanOrClose comparison.
-        /// </returns>
-        /// <param name="value1"> The first double to compare. </param>
-        /// <param name="value2"> The second double to compare. </param>
-        public static bool LessThanOrClose(double value1, double value2)
-        {
-            return (value1 < value2) || AreClose(value1, value2);
-        }
-    }
-}

src/Avalonia.Controls/Application.cs

@@ -30,7 +30,7 @@ namespace Avalonia
     /// method.
     /// - Tracks the lifetime of the application.
     /// </remarks>
-    public class Application : AvaloniaObject, IDataContextProvider, IGlobalDataTemplates, IGlobalStyles, IResourceNode
+    public class Application : AvaloniaObject, IDataContextProvider, IGlobalDataTemplates, IGlobalStyles, IResourceHost
     {
         /// <summary>
         /// The application-global data templates.
@@ -129,26 +129,13 @@ namespace Avalonia
         /// </summary>
         public IResourceDictionary Resources
         {
-            get => _resources ?? (Resources = new ResourceDictionary());
+            get => _resources ??= new ResourceDictionary(this);
             set
             {
-                Contract.Requires<ArgumentNullException>(value != null);
+                value = value ?? throw new ArgumentNullException(nameof(value));
-
+                _resources?.RemoveOwner(this);
-                var hadResources = false;
-
-                if (_resources != null)
-                {
-                    hadResources = _resources.Count > 0;
-                    _resources.ResourcesChanged -= ThisResourcesChanged;
-                }
-
                 _resources = value;
-                _resources.ResourcesChanged += ThisResourcesChanged;
+                _resources.AddOwner(this);
-
-                if (hadResources || _resources.Count > 0)
-                {
-                    ResourcesChanged?.Invoke(this, new ResourcesChangedEventArgs());
-                }
             }
         }
 
@@ -161,23 +148,15 @@ namespace Avalonia
         /// <remarks>
         /// Global styles apply to all windows in the application.
         /// </remarks>
-        public Styles Styles
+        public Styles Styles => _styles ??= new Styles(this);
-        {
-            get
-            {
-                if (_styles == null)
-                {
-                    _styles = new Styles(this);
-                    _styles.ResourcesChanged += ThisResourcesChanged;
-                }
-
-                return _styles;
-            }
-        }
 
         /// <inheritdoc/>
         bool IDataTemplateHost.IsDataTemplatesInitialized => _dataTemplates != null;
 
+        /// <inheritdoc/>
+        bool IResourceNode.HasResources => (_resources?.HasResources ?? false) ||
+            (((IResourceNode?)_styles)?.HasResources ?? false);
+
         /// <summary>
         /// Gets the styling parent of the application, which is null.
         /// </summary>
@@ -185,13 +164,7 @@ namespace Avalonia
 
         /// <inheritdoc/>
         bool IStyleHost.IsStylesInitialized => _styles != null;
-
+       
-        /// <inheritdoc/>
-        bool IResourceProvider.HasResources => _resources?.Count > 0;
-
-        /// <inheritdoc/>
-        IResourceNode IResourceNode.ResourceParent => null;
-        
         /// <summary>
         /// Application lifetime, use it for things like setting the main window and exiting the app from code
         /// Currently supported lifetimes are:
@@ -219,13 +192,18 @@ namespace Avalonia
         public virtual void Initialize() { }
 
         /// <inheritdoc/>
-        bool IResourceProvider.TryGetResource(object key, out object value)
+        bool IResourceNode.TryGetResource(object key, out object value)
         {
             value = null;
             return (_resources?.TryGetResource(key, out value) ?? false) ||
                    Styles.TryGetResource(key, out value);
         }
 
+        void IResourceHost.NotifyHostedResourcesChanged(ResourcesChangedEventArgs e)
+        {
+            ResourcesChanged?.Invoke(this, e);
+        }
+
         void IStyleHost.StylesAdded(IReadOnlyList<IStyle> styles)
         {
             _stylesAdded?.Invoke(styles);
@@ -254,8 +232,12 @@ namespace Avalonia
                 .Bind<IKeyboardNavigationHandler>().ToTransient<KeyboardNavigationHandler>()
                 .Bind<IStyler>().ToConstant(_styler)
                 .Bind<IScheduler>().ToConstant(AvaloniaScheduler.Instance)
-                .Bind<IDragDropDevice>().ToConstant(DragDropDevice.Instance)
+                .Bind<IDragDropDevice>().ToConstant(DragDropDevice.Instance);
-                .Bind<IPlatformDragSource>().ToTransient<InProcessDragSource>();
+            
+            // TODO: Fix this, for now we keep this behavior since someone might be relying on it in 0.9.x
+            if (AvaloniaLocator.Current.GetService<IPlatformDragSource>() == null)
+                AvaloniaLocator.CurrentMutable
+                    .Bind<IPlatformDragSource>().ToTransient<InProcessDragSource>();
 
             var clock = new RenderLoopClock();
             AvaloniaLocator.CurrentMutable
@@ -278,9 +260,7 @@ namespace Avalonia
             try
             {
                 _notifyingResourcesChanged = true;
-                (_resources as ISetResourceParent)?.ParentResourcesChanged(e);
+                ResourcesChanged?.Invoke(this, ResourcesChangedEventArgs.Empty);
-                (_styles as ISetResourceParent)?.ParentResourcesChanged(e);
-                ResourcesChanged?.Invoke(this, new ResourcesChangedEventArgs());
             }
             finally
             {

src/Avalonia.Controls/AutoCompleteBox.cs

@@ -10,6 +10,7 @@ using System.Collections.ObjectModel;
 using System.Collections.Specialized;
 using System.ComponentModel;
 using System.Linq;
+using System.Reactive.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using Avalonia.Collections;
@@ -467,10 +468,11 @@ namespace Avalonia.Controls
         /// <see cref="P:Avalonia.Controls.AutoCompleteBox.Text" />
         /// dependency property.</value>
         public static readonly DirectProperty<AutoCompleteBox, string> TextProperty =
-            AvaloniaProperty.RegisterDirect<AutoCompleteBox, string>(
+            TextBlock.TextProperty.AddOwnerWithDataValidation<AutoCompleteBox>(
-                nameof(Text),
                 o => o.Text,
-                (o, v) => o.Text = v);
+                (o, v) => o.Text = v,
+                defaultBindingMode: BindingMode.TwoWay,
+                enableDataValidation: true);
 
         /// <summary>
         /// Identifies the
@@ -1100,6 +1102,7 @@ namespace Avalonia.Controls
                 {
                     _textBoxSubscriptions =
                         _textBox.GetObservable(TextBox.TextProperty)
+                                .Skip(1)
                                 .Subscribe(_ => OnTextBoxTextChanged());
 
                     if (Text != null)
@@ -1242,6 +1245,20 @@ namespace Avalonia.Controls
 
             base.OnApplyTemplate(e);
         }
+        
+        /// <summary>
+        /// Called to update the validation state for properties for which data validation is
+        /// enabled.
+        /// </summary>
+        /// <param name="property">The property.</param>
+        /// <param name="value">The new binding value for the property.</param>
+        protected override void UpdateDataValidation<T>(AvaloniaProperty<T> property, BindingValue<T> value)
+        {
+            if (property == TextProperty)
+            {
+                DataValidationErrors.SetError(this, value.Error);
+            }
+        }
 
         /// <summary>
         /// Provides handling for the

src/Avalonia.Controls/Button.cs

@@ -313,17 +313,13 @@ namespace Avalonia.Controls
             IsPressed = false;
         }
 
-        protected override void OnPropertyChanged<T>(
+        protected override void OnPropertyChanged<T>(AvaloniaPropertyChangedEventArgs<T> change)
-            AvaloniaProperty<T> property,
-            Optional<T> oldValue,
-            BindingValue<T> newValue,
-            BindingPriority priority)
         {
-            base.OnPropertyChanged(property, oldValue, newValue, priority);
+            base.OnPropertyChanged(change);
 
-            if (property == IsPressedProperty)
+            if (change.Property == IsPressedProperty)
             {
-                UpdatePseudoClasses(newValue.GetValueOrDefault<bool>());
+                UpdatePseudoClasses(change.NewValue.GetValueOrDefault<bool>());
             }
         }
 

src/Avalonia.Controls/ButtonSpinner.cs

@@ -205,17 +205,13 @@ namespace Avalonia.Controls
             }
         }
 
-        protected override void OnPropertyChanged<T>(
+        protected override void OnPropertyChanged<T>(AvaloniaPropertyChangedEventArgs<T> change)
-            AvaloniaProperty<T> property,
-            Optional<T> oldValue,
-            BindingValue<T> newValue,
-            BindingPriority priority)
         {
-            base.OnPropertyChanged(property, oldValue, newValue, priority);
+            base.OnPropertyChanged(change);
 
-            if (property == ButtonSpinnerLocationProperty)
+            if (change.Property == ButtonSpinnerLocationProperty)
             {
-                UpdatePseudoClasses(newValue.GetValueOrDefault<Location>());
+                UpdatePseudoClasses(change.NewValue.GetValueOrDefault<Location>());
             }
         }
 

src/Avalonia.Controls/Calendar/Calendar.cs

@@ -998,10 +998,10 @@ namespace Avalonia.Controls
 
 
         /// <summary>
-        /// Gets or sets a value indicating whether DatePicker should change its 
+        /// Gets or sets a value indicating whether CalendarDatePicker should change its 
         /// DisplayDate because of a SelectedDate change on its Calendar.
         /// </summary>
-        internal bool DatePickerDisplayDateFlag { get; set; }
+        internal bool CalendarDatePickerDisplayDateFlag { get; set; }
 
         internal CalendarDayButton FindDayButtonFromDay(DateTime day)
         {

src/Avalonia.Controls/Calendar/DatePicker.cs → src/Avalonia.Controls/Calendar/CalendarDatePicker.cs

@@ -16,29 +16,29 @@ namespace Avalonia.Controls
 {
     /// <summary>
     /// Provides data for the
-    /// <see cref="E:Avalonia.Controls.DatePicker.DateValidationError" />
+    /// <see cref="E:Avalonia.Controls.CalendarDatePicker.DateValidationError" />
     /// event.
     /// </summary>
-    public class DatePickerDateValidationErrorEventArgs : EventArgs
+    public class CalendarDatePickerDateValidationErrorEventArgs : EventArgs
     {
         private bool _throwException;
 
         /// <summary>
         /// Initializes a new instance of the
-        /// <see cref="T:Avalonia.Controls.DatePickerDateValidationErrorEventArgs" />
+        /// <see cref="T:Avalonia.Controls.CalendarDatePickerDateValidationErrorEventArgs" />
         /// class.
         /// </summary>
         /// <param name="exception">
         /// The initial exception from the
-        /// <see cref="E:Avalonia.Controls.DatePicker.DateValidationError" />
+        /// <see cref="E:Avalonia.Controls.CalendarDatePicker.DateValidationError" />
         /// event.
         /// </param>
         /// <param name="text">
         /// The text that caused the
-        /// <see cref="E:Avalonia.Controls.DatePicker.DateValidationError" />
+        /// <see cref="E:Avalonia.Controls.CalendarDatePicker.DateValidationError" />
         /// event.
         /// </param>
-        public DatePickerDateValidationErrorEventArgs(Exception exception, string text)
+        public CalendarDatePickerDateValidationErrorEventArgs(Exception exception, string text)
         {
             this.Text = text;
             this.Exception = exception;
@@ -46,7 +46,7 @@ namespace Avalonia.Controls
 
         /// <summary>
         /// Gets the initial exception associated with the
-        /// <see cref="E:Avalonia.Controls.DatePicker.DateValidationError" />
+        /// <see cref="E:Avalonia.Controls.CalendarDatePicker.DateValidationError" />
         /// event.
         /// </summary>
         /// <value>
@@ -56,7 +56,7 @@ namespace Avalonia.Controls
 
         /// <summary>
         /// Gets the text that caused the
-        /// <see cref="E:Avalonia.Controls.DatePicker.DateValidationError" />
+        /// <see cref="E:Avalonia.Controls.CalendarDatePicker.DateValidationError" />
         /// event.
         /// </summary>
         /// <value>
@@ -66,7 +66,7 @@ namespace Avalonia.Controls
 
         /// <summary>
         /// Gets or sets a value indicating whether
-        /// <see cref="P:Avalonia.Controls.DatePickerDateValidationErrorEventArgs.Exception" />
+        /// <see cref="P:Avalonia.Controls.CalendarDatePickerDateValidationErrorEventArgs.Exception" />
         /// should be thrown.
         /// </summary>
         /// <value>
@@ -74,7 +74,7 @@ namespace Avalonia.Controls
         /// </value>
         /// <exception cref="T:System.ArgumentException">
         /// If set to true and
-        /// <see cref="P:Avalonia.Controls.DatePickerDateValidationErrorEventArgs.Exception" />
+        /// <see cref="P:Avalonia.Controls.CalendarDatePickerDateValidationErrorEventArgs.Exception" />
         /// is null.
         /// </exception>
         public bool ThrowException
@@ -93,9 +93,9 @@ namespace Avalonia.Controls
 
     /// <summary>
     /// Specifies date formats for a
-    /// <see cref="T:Avalonia.Controls.DatePicker" />.
+    /// <see cref="T:Avalonia.Controls.CalendarDatePicker" />.
     /// </summary>
-    public enum DatePickerFormat
+    public enum CalendarDatePickerFormat
     {
         /// <summary>
         /// Specifies that the date should be displayed using unabbreviated days
@@ -115,7 +115,7 @@ namespace Avalonia.Controls
         Custom = 2
     }
 
-    public class DatePicker : TemplatedControl
+    public class CalendarDatePicker : TemplatedControl
     {
         private const string ElementTextBox = "PART_TextBox";
         private const string ElementButton = "PART_Button";
@@ -154,59 +154,59 @@ namespace Avalonia.Controls
         /// </value>
         public CalendarBlackoutDatesCollection BlackoutDates { get; private set; }
 
-        public static readonly DirectProperty<DatePicker, DateTime> DisplayDateProperty =
+        public static readonly DirectProperty<CalendarDatePicker, DateTime> DisplayDateProperty =
-            AvaloniaProperty.RegisterDirect<DatePicker, DateTime>(
+            AvaloniaProperty.RegisterDirect<CalendarDatePicker, DateTime>(
                 nameof(DisplayDate),
                 o => o.DisplayDate,
                 (o, v) => o.DisplayDate = v);
-        public static readonly DirectProperty<DatePicker, DateTime?> DisplayDateStartProperty =
+        public static readonly DirectProperty<CalendarDatePicker, DateTime?> DisplayDateStartProperty =
-            AvaloniaProperty.RegisterDirect<DatePicker, DateTime?>(
+            AvaloniaProperty.RegisterDirect<CalendarDatePicker, DateTime?>(
                 nameof(DisplayDateStart),
                 o => o.DisplayDateStart,
                 (o, v) => o.DisplayDateStart = v);
-        public static readonly DirectProperty<DatePicker, DateTime?> DisplayDateEndProperty =
+        public static readonly DirectProperty<CalendarDatePicker, DateTime?> DisplayDateEndProperty =
-            AvaloniaProperty.RegisterDirect<DatePicker, DateTime?>(
+            AvaloniaProperty.RegisterDirect<CalendarDatePicker, DateTime?>(
                 nameof(DisplayDateEnd),
                 o => o.DisplayDateEnd,
                 (o, v) => o.DisplayDateEnd = v);
         public static readonly StyledProperty<DayOfWeek> FirstDayOfWeekProperty =
-            AvaloniaProperty.Register<DatePicker, DayOfWeek>(nameof(FirstDayOfWeek));
+            AvaloniaProperty.Register<CalendarDatePicker, DayOfWeek>(nameof(FirstDayOfWeek));
 
-        public static readonly DirectProperty<DatePicker, bool> IsDropDownOpenProperty =
+        public static readonly DirectProperty<CalendarDatePicker, bool> IsDropDownOpenProperty =
-            AvaloniaProperty.RegisterDirect<DatePicker, bool>(
+            AvaloniaProperty.RegisterDirect<CalendarDatePicker, bool>(
                 nameof(IsDropDownOpen),
                 o => o.IsDropDownOpen,
                 (o, v) => o.IsDropDownOpen = v);
 
         public static readonly StyledProperty<bool> IsTodayHighlightedProperty =
-            AvaloniaProperty.Register<DatePicker, bool>(nameof(IsTodayHighlighted));
+            AvaloniaProperty.Register<CalendarDatePicker, bool>(nameof(IsTodayHighlighted));
-        public static readonly DirectProperty<DatePicker, DateTime?> SelectedDateProperty =
+        public static readonly DirectProperty<CalendarDatePicker, DateTime?> SelectedDateProperty =
-            AvaloniaProperty.RegisterDirect<DatePicker, DateTime?>(
+            AvaloniaProperty.RegisterDirect<CalendarDatePicker, DateTime?>(
                 nameof(SelectedDate),
                 o => o.SelectedDate,
                 (o, v) => o.SelectedDate = v);
 
-        public static readonly StyledProperty<DatePickerFormat> SelectedDateFormatProperty =
+        public static readonly StyledProperty<CalendarDatePickerFormat> SelectedDateFormatProperty =
-            AvaloniaProperty.Register<DatePicker, DatePickerFormat>(
+            AvaloniaProperty.Register<CalendarDatePicker, CalendarDatePickerFormat>(
                 nameof(SelectedDateFormat),
-                defaultValue: DatePickerFormat.Short,
+                defaultValue: CalendarDatePickerFormat.Short,
                 validate: IsValidSelectedDateFormat);
 
         public static readonly StyledProperty<string> CustomDateFormatStringProperty =
-            AvaloniaProperty.Register<DatePicker, string>(
+            AvaloniaProperty.Register<CalendarDatePicker, string>(
                 nameof(CustomDateFormatString),
                 defaultValue: "d",
                 validate: IsValidDateFormatString);
 
-        public static readonly DirectProperty<DatePicker, string> TextProperty =
+        public static readonly DirectProperty<CalendarDatePicker, string> TextProperty =
-            AvaloniaProperty.RegisterDirect<DatePicker, string>(
+            AvaloniaProperty.RegisterDirect<CalendarDatePicker, string>(
                 nameof(Text),
                 o => o.Text,
                 (o, v) => o.Text = v);
         public static readonly StyledProperty<string> WatermarkProperty =
-            TextBox.WatermarkProperty.AddOwner<DatePicker>();
+            TextBox.WatermarkProperty.AddOwner<CalendarDatePicker>();
         public static readonly StyledProperty<bool> UseFloatingWatermarkProperty =
-            TextBox.UseFloatingWatermarkProperty.AddOwner<DatePicker>();
+            TextBox.UseFloatingWatermarkProperty.AddOwner<CalendarDatePicker>();
 
 
         /// <summary>
@@ -218,9 +218,9 @@ namespace Avalonia.Controls
         /// </value>
         /// <exception cref="T:System.ArgumentOutOfRangeException">
         /// The specified date is not in the range defined by
-        /// <see cref="P:Avalonia.Controls.DatePicker.DisplayDateStart" />
+        /// <see cref="P:Avalonia.Controls.CalendarDatePicker.DisplayDateStart" />
         /// and
-        /// <see cref="P:Avalonia.Controls.DatePicker.DisplayDateEnd" />.
+        /// <see cref="P:Avalonia.Controls.CalendarDatePicker.DisplayDateEnd" />.
         /// </exception>
         public DateTime DisplayDate
         {
@@ -320,7 +320,7 @@ namespace Avalonia.Controls
         /// <exception cref="T:System.ArgumentOutOfRangeException">
         /// An specified format is not valid.
         /// </exception>
-        public DatePickerFormat SelectedDateFormat
+        public CalendarDatePickerFormat SelectedDateFormat
         {
             get { return GetValue(SelectedDateFormatProperty); }
             set { SetValue(SelectedDateFormatProperty, value); }
@@ -380,33 +380,33 @@ namespace Avalonia.Controls
         /// Occurs when <see cref="P:Avalonia.Controls.DatePicker.Text" />
         /// is assigned a value that cannot be interpreted as a date.
         /// </summary>
-        public event EventHandler<DatePickerDateValidationErrorEventArgs> DateValidationError;
+        public event EventHandler<CalendarDatePickerDateValidationErrorEventArgs> DateValidationError;
 
         /// <summary>
         /// Occurs when the
-        /// <see cref="P:Avalonia.Controls.DatePicker.SelectedDate" />
+        /// <see cref="P:Avalonia.Controls.CalendarDatePicker.SelectedDate" />
         /// property is changed.
         /// </summary>
         public event EventHandler<SelectionChangedEventArgs> SelectedDateChanged;
 
-        static DatePicker()
+        static CalendarDatePicker()
         {
-            FocusableProperty.OverrideDefaultValue<DatePicker>(true);
+            FocusableProperty.OverrideDefaultValue<CalendarDatePicker>(true);
-
+
-            DisplayDateProperty.Changed.AddClassHandler<DatePicker>((x,e) => x.OnDisplayDateChanged(e));
+            DisplayDateProperty.Changed.AddClassHandler<CalendarDatePicker>((x,e) => x.OnDisplayDateChanged(e));
-            DisplayDateStartProperty.Changed.AddClassHandler<DatePicker>((x,e) => x.OnDisplayDateStartChanged(e));
+            DisplayDateStartProperty.Changed.AddClassHandler<CalendarDatePicker>((x,e) => x.OnDisplayDateStartChanged(e));
-            DisplayDateEndProperty.Changed.AddClassHandler<DatePicker>((x,e) => x.OnDisplayDateEndChanged(e));
+            DisplayDateEndProperty.Changed.AddClassHandler<CalendarDatePicker>((x,e) => x.OnDisplayDateEndChanged(e));
-            IsDropDownOpenProperty.Changed.AddClassHandler<DatePicker>((x,e) => x.OnIsDropDownOpenChanged(e));
+            IsDropDownOpenProperty.Changed.AddClassHandler<CalendarDatePicker>((x,e) => x.OnIsDropDownOpenChanged(e));
-            SelectedDateProperty.Changed.AddClassHandler<DatePicker>((x,e) => x.OnSelectedDateChanged(e));
+            SelectedDateProperty.Changed.AddClassHandler<CalendarDatePicker>((x,e) => x.OnSelectedDateChanged(e));
-            SelectedDateFormatProperty.Changed.AddClassHandler<DatePicker>((x,e) => x.OnSelectedDateFormatChanged(e));
+            SelectedDateFormatProperty.Changed.AddClassHandler<CalendarDatePicker>((x,e) => x.OnSelectedDateFormatChanged(e));
-            CustomDateFormatStringProperty.Changed.AddClassHandler<DatePicker>((x,e) => x.OnCustomDateFormatStringChanged(e));
+            CustomDateFormatStringProperty.Changed.AddClassHandler<CalendarDatePicker>((x,e) => x.OnCustomDateFormatStringChanged(e));
-            TextProperty.Changed.AddClassHandler<DatePicker>((x,e) => x.OnTextChanged(e));
+            TextProperty.Changed.AddClassHandler<CalendarDatePicker>((x,e) => x.OnTextChanged(e));
         }
         /// <summary>
         /// Initializes a new instance of the
         /// <see cref="T:Avalonia.Controls.DatePicker" /> class.
         /// </summary>
-        public DatePicker()
+        public CalendarDatePicker()
         {
             FirstDayOfWeek = DateTimeHelper.GetCurrentDateFormat().FirstDayOfWeek;
             _defaultText = string.Empty;
@@ -510,17 +510,13 @@ namespace Avalonia.Controls
             }
         }
 
-        protected override void OnPropertyChanged<T>(
+        protected override void OnPropertyChanged<T>(AvaloniaPropertyChangedEventArgs<T> change)
-            AvaloniaProperty<T> property,
-            Optional<T> oldValue,
-            BindingValue<T> newValue,
-            BindingPriority priority)
         {
-            base.OnPropertyChanged(property, oldValue, newValue, priority);
+            base.OnPropertyChanged(change);
 
-            if (property == SelectedDateProperty)
+            if (change.Property == SelectedDateProperty)
             {
-                DataValidationErrors.SetError(this, newValue.Error);
+                DataValidationErrors.SetError(this, change.NewValue.Error);
             }
         }
 
@@ -666,12 +662,12 @@ namespace Avalonia.Controls
                 // change is coming from the Calendar UI itself, so, we
                 // shouldn't change the DisplayDate since it will automatically
                 // be changed by the Calendar
-                if ((day.Month != DisplayDate.Month || day.Year != DisplayDate.Year) && (_calendar == null || !_calendar.DatePickerDisplayDateFlag))
+                if ((day.Month != DisplayDate.Month || day.Year != DisplayDate.Year) && (_calendar == null || !_calendar.CalendarDatePickerDisplayDateFlag))
                 {
                     DisplayDate = day;
                 }
                 if(_calendar != null)
-                    _calendar.DatePickerDisplayDateFlag = false;
+                    _calendar.CalendarDatePickerDisplayDateFlag = false;
             }
             else
             {
@@ -711,7 +707,7 @@ namespace Avalonia.Controls
         }
         private void OnCustomDateFormatStringChanged(AvaloniaPropertyChangedEventArgs e)
         {
-            if(SelectedDateFormat == DatePickerFormat.Custom)
+            if(SelectedDateFormat == CalendarDatePickerFormat.Custom)
             {
                 OnDateFormatChanged();
             }
@@ -756,15 +752,15 @@ namespace Avalonia.Controls
 
         /// <summary>
         /// Raises the
-        /// <see cref="E:Avalonia.Controls.DatePicker.DateValidationError" />
+        /// <see cref="E:Avalonia.Controls.CalendarDatePicker.DateValidationError" />
         /// event.
         /// </summary>
         /// <param name="e">
         /// A
-        /// <see cref="T:Avalonia.Controls.DatePickerDateValidationErrorEventArgs" />
+        /// <see cref="T:Avalonia.Controls.CalendarDatePickerDateValidationErrorEventArgs" />
         /// that contains the event data.
         /// </param>
-        protected virtual void OnDateValidationError(DatePickerDateValidationErrorEventArgs e)
+        protected virtual void OnDateValidationError(CalendarDatePickerDateValidationErrorEventArgs e)
         {
             DateValidationError?.Invoke(this, e);
         }
@@ -963,7 +959,7 @@ namespace Avalonia.Controls
                 }
                 else
                 {
-                    var dateValidationError = new DatePickerDateValidationErrorEventArgs(new ArgumentOutOfRangeException(nameof(text), "SelectedDate value is not valid."), text);
+                    var dateValidationError = new CalendarDatePickerDateValidationErrorEventArgs(new ArgumentOutOfRangeException(nameof(text), "SelectedDate value is not valid."), text);
                     OnDateValidationError(dateValidationError);
 
                     if (dateValidationError.ThrowException)
@@ -974,7 +970,7 @@ namespace Avalonia.Controls
             }
             catch (FormatException ex)
             {
-                DatePickerDateValidationErrorEventArgs textParseError = new DatePickerDateValidationErrorEventArgs(ex, text);
+                CalendarDatePickerDateValidationErrorEventArgs textParseError = new CalendarDatePickerDateValidationErrorEventArgs(ex, text);
                 OnDateValidationError(textParseError);
 
                 if (textParseError.ThrowException)
@@ -990,11 +986,11 @@ namespace Avalonia.Controls
 
             switch (SelectedDateFormat)
             {
-                case DatePickerFormat.Short:
+                case CalendarDatePickerFormat.Short:
                     return string.Format(CultureInfo.CurrentCulture, d.ToString(dtfi.ShortDatePattern, dtfi));
-                case DatePickerFormat.Long:
+                case CalendarDatePickerFormat.Long:
                     return string.Format(CultureInfo.CurrentCulture, d.ToString(dtfi.LongDatePattern, dtfi));
-                case DatePickerFormat.Custom:
+                case CalendarDatePickerFormat.Custom:
                     return string.Format(CultureInfo.CurrentCulture, d.ToString(CustomDateFormatString, dtfi));
             }
             return null;
@@ -1122,12 +1118,12 @@ namespace Avalonia.Controls
 
                     switch (SelectedDateFormat)
                     {
-                        case DatePickerFormat.Long:
+                        case CalendarDatePickerFormat.Long:
                             {
                                 watermarkText = string.Format(CultureInfo.CurrentCulture, watermarkFormat, dtfi.LongDatePattern.ToString());
                                 break;
                             }
-                        case DatePickerFormat.Short:
+                        case CalendarDatePickerFormat.Short:
                         default:
                             {
                                 watermarkText = string.Format(CultureInfo.CurrentCulture, watermarkFormat, dtfi.ShortDatePattern.ToString());
@@ -1143,11 +1139,11 @@ namespace Avalonia.Controls
             }
         }
 
-        private static bool IsValidSelectedDateFormat(DatePickerFormat value)
+        private static bool IsValidSelectedDateFormat(CalendarDatePickerFormat value)
         {
-            return value == DatePickerFormat.Long
+            return value == CalendarDatePickerFormat.Long
-                || value == DatePickerFormat.Short
+                || value == CalendarDatePickerFormat.Short
-                || value == DatePickerFormat.Custom;
+                || value == CalendarDatePickerFormat.Custom;
         }
         private static bool IsValidDateFormatString(string formatString)
         {

src/Avalonia.Controls/Calendar/CalendarItem.cs

@@ -909,7 +909,7 @@ namespace Avalonia.Controls.Primitives
                         case CalendarSelectionMode.SingleDate:
                             {
                                 DateTime selectedDate = (DateTime)b.DataContext;
-                                Owner.DatePickerDisplayDateFlag = true;
+                                Owner.CalendarDatePickerDisplayDateFlag = true;
                                 if (Owner.SelectedDates.Count == 0)
                                 {
                                     Owner.SelectedDates.Add(selectedDate);
@@ -981,7 +981,7 @@ namespace Avalonia.Controls.Primitives
                                 }
                             case CalendarSelectionMode.SingleDate:
                                 {
-                                    Owner.DatePickerDisplayDateFlag = true;
+                                    Owner.CalendarDatePickerDisplayDateFlag = true;
                                     if (Owner.SelectedDates.Count == 0)
                                     {
                                         Owner.SelectedDates.Add(selectedDate);

src/Avalonia.Controls/ComboBox.cs

@@ -51,6 +51,18 @@ namespace Avalonia.Controls
         public static readonly StyledProperty<ItemVirtualizationMode> VirtualizationModeProperty =
             ItemsPresenter.VirtualizationModeProperty.AddOwner<ComboBox>();
 
+        /// <summary>
+        /// Defines the <see cref="PlaceholderText"/> property.
+        /// </summary>
+        public static readonly StyledProperty<string> PlaceholderTextProperty =
+            AvaloniaProperty.Register<ComboBox, string>(nameof(PlaceholderText));
+
+        /// <summary>
+        /// Defines the <see cref="PlaceholderForeground"/> property.
+        /// </summary>
+        public static readonly StyledProperty<IBrush> PlaceholderForegroundProperty =
+            AvaloniaProperty.Register<ComboBox, IBrush>(nameof(PlaceholderForeground));
+
         private bool _isDropDownOpen;
         private Popup _popup;
         private object _selectionBoxItem;
@@ -94,6 +106,24 @@ namespace Avalonia.Controls
             set { SetAndRaise(SelectionBoxItemProperty, ref _selectionBoxItem, value); }
         }
 
+        /// <summary>
+        /// Gets or sets the PlaceHolder text.
+        /// </summary>
+        public string PlaceholderText
+        {
+            get { return GetValue(PlaceholderTextProperty); }
+            set { SetValue(PlaceholderTextProperty, value); }
+        }
+
+        /// <summary>
+        /// Gets or sets the Brush that renders the placeholder text.
+        /// </summary>
+        public IBrush PlaceholderForeground
+        {
+            get { return GetValue(PlaceholderForegroundProperty); }
+            set { SetValue(PlaceholderForegroundProperty, value); }
+        }
+
         /// <summary>
         /// Gets or sets the virtualization mode for the items.
         /// </summary>

src/Avalonia.Controls/ContextMenu.cs

@@ -1,27 +1,78 @@
 using System;
+using System.Collections.Generic;
 using System.ComponentModel;
-using System.Linq;
 using Avalonia.Controls.Generators;
 using Avalonia.Controls.Platform;
 using Avalonia.Controls.Primitives;
+using Avalonia.Controls.Primitives.PopupPositioning;
 using Avalonia.Controls.Templates;
 using Avalonia.Input;
 using Avalonia.Interactivity;
 using Avalonia.Layout;
-using Avalonia.LogicalTree;
+using Avalonia.Styling;
+
+#nullable enable
 
 namespace Avalonia.Controls
 {
     /// <summary>
     /// A control context menu.
     /// </summary>
-    public class ContextMenu : MenuBase
+    public class ContextMenu : MenuBase, ISetterValue
     {
+        /// <summary>
+        /// Defines the <see cref="HorizontalOffset"/> property.
+        /// </summary>
+        public static readonly StyledProperty<double> HorizontalOffsetProperty =
+            Popup.HorizontalOffsetProperty.AddOwner<ContextMenu>();
+
+        /// <summary>
+        /// Defines the <see cref="VerticalOffset"/> property.
+        /// </summary>
+        public static readonly StyledProperty<double> VerticalOffsetProperty =
+            Popup.VerticalOffsetProperty.AddOwner<ContextMenu>();
+
+        /// <summary>
+        /// Defines the <see cref="PlacementAnchor"/> property.
+        /// </summary>
+        public static readonly StyledProperty<PopupAnchor> PlacementAnchorProperty =
+            Popup.PlacementAnchorProperty.AddOwner<ContextMenu>();
+
+        /// <summary>
+        /// Defines the <see cref="PlacementConstraintAdjustment"/> property.
+        /// </summary>
+        public static readonly StyledProperty<PopupPositionerConstraintAdjustment> PlacementConstraintAdjustmentProperty =
+            Popup.PlacementConstraintAdjustmentProperty.AddOwner<ContextMenu>();
+
+        /// <summary>
+        /// Defines the <see cref="PlacementGravity"/> property.
+        /// </summary>
+        public static readonly StyledProperty<PopupGravity> PlacementGravityProperty =
+            Popup.PlacementGravityProperty.AddOwner<ContextMenu>();
+
+        /// <summary>
+        /// Defines the <see cref="PlacementMode"/> property.
+        /// </summary>
+        public static readonly StyledProperty<PlacementMode> PlacementModeProperty =
+            Popup.PlacementModeProperty.AddOwner<ContextMenu>();
+
+        /// <summary>
+        /// Defines the <see cref="PlacementRect"/> property.
+        /// </summary>
+        public static readonly StyledProperty<Rect?> PlacementRectProperty =
+            AvaloniaProperty.Register<Popup, Rect?>(nameof(PlacementRect));
+
+        /// <summary>
+        /// Defines the <see cref="PlacementTarget"/> property.
+        /// </summary>
+        public static readonly StyledProperty<Control?> PlacementTargetProperty =
+            Popup.PlacementTargetProperty.AddOwner<ContextMenu>();
+
         private static readonly ITemplate<IPanel> DefaultPanel =
             new FuncTemplate<IPanel>(() => new StackPanel { Orientation = Orientation.Vertical });
-        private Popup _popup;
+        private Popup? _popup;
-        private Control _attachedControl;
+        private List<Control>? _attachedControls;
-        private IInputElement _previousFocus;
+        private IInputElement? _previousFocus;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="ContextMenu"/> class.
@@ -45,23 +96,107 @@ namespace Avalonia.Controls
         /// </summary>
         static ContextMenu()
         {
-            ItemsPanelProperty.OverrideDefaultValue(typeof(ContextMenu), DefaultPanel);
+            ItemsPanelProperty.OverrideDefaultValue<ContextMenu>(DefaultPanel);
+            PlacementModeProperty.OverrideDefaultValue<ContextMenu>(PlacementMode.Pointer);
             ContextMenuProperty.Changed.Subscribe(ContextMenuChanged);
         }
 
+        /// <summary>
+        /// Gets or sets the Horizontal offset of the context menu in relation to the <see cref="PlacementTarget"/>.
+        /// </summary>
+        public double HorizontalOffset
+        {
+            get { return GetValue(HorizontalOffsetProperty); }
+            set { SetValue(HorizontalOffsetProperty, value); }
+        }
+
+        /// <summary>
+        /// Gets or sets the Vertical offset of the context menu in relation to the <see cref="PlacementTarget"/>.
+        /// </summary>
+        public double VerticalOffset
+        {
+            get { return GetValue(VerticalOffsetProperty); }
+            set { SetValue(VerticalOffsetProperty, value); }
+        }
+
+        /// <summary>
+        /// Gets or sets the anchor point on the <see cref="PlacementRect"/> when <see cref="PlacementMode"/>
+        /// is <see cref="PlacementMode.AnchorAndGravity"/>.
+        /// </summary>
+        public PopupAnchor PlacementAnchor
+        {
+            get { return GetValue(PlacementAnchorProperty); }
+            set { SetValue(PlacementAnchorProperty, value); }
+        }
+
+        /// <summary>
+        /// Gets or sets a value describing how the context menu position will be adjusted if the
+        /// unadjusted position would result in the context menu being partly constrained.
+        /// </summary>
+        public PopupPositionerConstraintAdjustment PlacementConstraintAdjustment
+        {
+            get { return GetValue(PlacementConstraintAdjustmentProperty); }
+            set { SetValue(PlacementConstraintAdjustmentProperty, value); }
+        }
+
+        /// <summary>
+        /// Gets or sets a value which defines in what direction the context menu should open
+        /// when <see cref="PlacementMode"/> is <see cref="PlacementMode.AnchorAndGravity"/>.
+        /// </summary>
+        public PopupGravity PlacementGravity
+        {
+            get { return GetValue(PlacementGravityProperty); }
+            set { SetValue(PlacementGravityProperty, value); }
+        }
+
+        /// <summary>
+        /// Gets or sets the placement mode of the context menu in relation to the<see cref="PlacementTarget"/>.
+        /// </summary>
+        public PlacementMode PlacementMode
+        {
+            get { return GetValue(PlacementModeProperty); }
+            set { SetValue(PlacementModeProperty, value); }
+        }
+
+        /// <summary>
+        /// Gets or sets the the anchor rectangle within the parent that the context menu will be placed
+        /// relative to when <see cref="PlacementMode"/> is <see cref="PlacementMode.AnchorAndGravity"/>.
+        /// </summary>
+        /// <remarks>
+        /// The placement rect defines a rectangle relative to <see cref="PlacementTarget"/> around
+        /// which the popup will be opened, with <see cref="PlacementAnchor"/> determining which edge
+        /// of the placement target is used.
+        /// 
+        /// If unset, the anchor rectangle will be the bounds of the <see cref="PlacementTarget"/>.
+        /// </remarks>
+        public Rect? PlacementRect
+        {
+            get { return GetValue(PlacementRectProperty); }
+            set { SetValue(PlacementRectProperty, value); }
+        }
+
+        /// <summary>
+        /// Gets or sets the control that is used to determine the popup's position.
+        /// </summary>
+        public Control? PlacementTarget
+        {
+            get { return GetValue(PlacementTargetProperty); }
+            set { SetValue(PlacementTargetProperty, value); }
+        }
+
         /// <summary>
         /// Occurs when the value of the
         /// <see cref="P:Avalonia.Controls.ContextMenu.IsOpen" />
         /// property is changing from false to true.
         /// </summary>
-        public event CancelEventHandler ContextMenuOpening;
+        public event CancelEventHandler? ContextMenuOpening;
 
         /// <summary>
         /// Occurs when the value of the
         /// <see cref="P:Avalonia.Controls.ContextMenu.IsOpen" />
         /// property is changing from true to false.
         /// </summary>
-        public event CancelEventHandler ContextMenuClosing;
+        public event CancelEventHandler? ContextMenuClosing;
 
         /// <summary>
         /// Called when the <see cref="Control.ContextMenu"/> property changes on a control.
@@ -74,13 +209,14 @@ namespace Avalonia.Controls
             if (e.OldValue is ContextMenu oldMenu)
             {
                 control.PointerReleased -= ControlPointerReleased;
-                oldMenu._attachedControl = null;
+                oldMenu._attachedControls?.Remove(control);
-                ((ISetLogicalParent)oldMenu._popup)?.SetParent(null);
+                ((ISetLogicalParent?)oldMenu._popup)?.SetParent(null);
             }
 
             if (e.NewValue is ContextMenu newMenu)
             {
-                newMenu._attachedControl = control;
+                newMenu._attachedControls ??= new List<Control>();
+                newMenu._attachedControls.Add(control);
                 control.PointerReleased += ControlPointerReleased;
             }
         }
@@ -94,20 +230,24 @@ namespace Avalonia.Controls
         /// Opens a context menu on the specified control.
         /// </summary>
         /// <param name="control">The control.</param>
-        public void Open(Control control)
+        public void Open(Control? control)
         {
-            if (control is null && _attachedControl is null)
+            if (control is null && (_attachedControls is null || _attachedControls.Count == 0))
             {
                 throw new ArgumentNullException(nameof(control));
             }
 
-            if (control is object && _attachedControl is object && control != _attachedControl)
+            if (control is object &&
+                _attachedControls is object &&
+                !_attachedControls.Contains(control))
             {
                 throw new ArgumentException(
                     "Cannot show ContentMenu on a different control to the one it is attached to.",
                     nameof(control));
             }
 
+            control ??= _attachedControls![0];
+
             if (IsOpen)
             {
                 return;
@@ -117,8 +257,14 @@ namespace Avalonia.Controls
             {
                 _popup = new Popup
                 {
-                    PlacementMode = PlacementMode.Pointer,
+                    HorizontalOffset = HorizontalOffset,
-                    PlacementTarget = control,
+                    VerticalOffset = VerticalOffset,
+                    PlacementAnchor = PlacementAnchor,
+                    PlacementConstraintAdjustment = PlacementConstraintAdjustment,
+                    PlacementGravity = PlacementGravity,
+                    PlacementMode = PlacementMode,
+                    PlacementRect = PlacementRect,
+                    PlacementTarget = PlacementTarget ?? control,
                     StaysOpen = false
                 };
 
@@ -126,7 +272,12 @@ namespace Avalonia.Controls
                 _popup.Closed += PopupClosed;
             }
 
-            ((ISetLogicalParent)_popup).SetParent(control);
+            if (_popup.Parent != control)
+            {
+                ((ISetLogicalParent)_popup).SetParent(null);
+                ((ISetLogicalParent)_popup).SetParent(control);
+            }
+
             _popup.Child = this;
             _popup.IsOpen = true;
 
@@ -155,6 +306,17 @@ namespace Avalonia.Controls
             }
         }
 
+        void ISetterValue.Initialize(ISetter setter)
+        {
+            // ContextMenu can be assigned to the ContextMenu property in a setter. This overrides
+            // the behavior defined in Control which requires controls to be wrapped in a <template>.
+            if (!(setter is Setter s && s.Property == ContextMenuProperty))
+            {
+                throw new InvalidOperationException(
+                    "Cannot use a control as a Setter value. Wrap the control in a <Template>.");
+            }
+        }
+
         protected override IItemContainerGenerator CreateItemContainerGenerator()
         {
             return new MenuItemContainerGenerator(this);
@@ -179,9 +341,9 @@ namespace Avalonia.Controls
             SelectedIndex = -1;
             IsOpen = false;
 
-            if (_attachedControl is null)
+            if (_attachedControls is null || _attachedControls.Count == 0)
             {
-                ((ISetLogicalParent)_popup).SetParent(null);
+                ((ISetLogicalParent)_popup!).SetParent(null);
             }
 
             // HACK: Reset the focus when the popup is closed. We need to fix this so it's automatic.

src/Avalonia.Controls/Converters/MarginMultiplierConverter.cs

@@ -18,10 +18,24 @@ namespace Avalonia.Controls.Converters
 
         public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
         {
-            if (!(value is int depth))
+            if (value is int scalarDepth)
-                return new Thickness(0);
+            {
-
+                return new Thickness(
-            return new Thickness(Left ? Indent * depth : 0, Top ? Indent * depth : 0, Right ? Indent * depth : 0, Bottom ? Indent * depth : 0);
+                    Left ? Indent * scalarDepth : 0,
+                    Top ? Indent * scalarDepth : 0,
+                    Right ? Indent * scalarDepth : 0,
+                    Bottom ? Indent * scalarDepth : 0);
+            }
+            else if (value is Thickness thinknessDepth)
+            {
+                return new Thickness(
+                    Left ? Indent * thinknessDepth.Left : 0,
+                    Top ? Indent * thinknessDepth.Top : 0,
+                    Right ? Indent * thinknessDepth.Right : 0,
+                    Bottom ? Indent * thinknessDepth.Bottom : 0);
+            }
+            return new Thickness(0);
+            
         }
 
         public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)

src/Avalonia.Controls/Converters/MenuScrollingVisibilityConverter.cs

@@ -0,0 +1,64 @@
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using Avalonia.Controls.Primitives;
+using Avalonia.Data.Converters;
+using Avalonia.Utilities;
+
+namespace Avalonia.Controls.Converters
+{
+    public class MenuScrollingVisibilityConverter : IMultiValueConverter
+    {
+        public static readonly MenuScrollingVisibilityConverter Instance = new MenuScrollingVisibilityConverter();
+
+        public object Convert(IList<object> values, Type targetType, object parameter, CultureInfo culture)
+        {
+            if (parameter == null ||
+                values == null ||
+                values.Count != 4 ||
+                !(values[0] is ScrollBarVisibility visiblity) ||
+                !(values[1] is double offset) ||
+                !(values[2] is double extent) ||
+                !(values[3] is double viewport))
+            {
+                return AvaloniaProperty.UnsetValue;
+            }
+
+            if (visiblity == ScrollBarVisibility.Auto)
+            {
+                if (extent == viewport)
+                {
+                    return false;
+                }
+
+                double target;
+
+                if (parameter is double d)
+                {
+                    target = d;
+                }
+                else if (parameter is string s)
+                {
+                    target = double.Parse(s, NumberFormatInfo.InvariantInfo);
+                }
+                else
+                {
+                    return AvaloniaProperty.UnsetValue;
+                }
+
+                // Calculate the percent so that we can see if we are near the edge of the range
+                double percent = MathUtilities.Clamp(offset * 100.0 / (extent - viewport), 0, 100);
+
+                if (MathUtilities.AreClose(percent, target))
+                {
+                    // We are at the end of the range, so no need for this button to be shown
+                    return false;
+                }
+
+                return true;
+            }
+
+            return false;
+        }
+    }
+}

src/Avalonia.Controls/Embedding/Offscreen/OffscreenTopLevelImpl.cs

@@ -49,6 +49,9 @@ namespace Avalonia.Controls.Embedding.Offscreen
         public Action<Rect> Paint { get; set; }
         public Action<Size> Resized { get; set; }
         public Action<double> ScalingChanged { get; set; }
+
+        public Action<WindowTransparencyLevel> TransparencyLevelChanged { get; set; }
+
         public void SetInputRoot(IInputRoot inputRoot) => InputRoot = inputRoot;
 
         public virtual Point PointToClient(PixelPoint point) => point.ToPoint(1);
@@ -61,6 +64,11 @@ namespace Avalonia.Controls.Embedding.Offscreen
 
         public Action Closed { get; set; }
         public abstract IMouseDevice MouseDevice { get; }
+
+        public void SetTransparencyLevelHint(WindowTransparencyLevel transparencyLevel) { }
+
+        public WindowTransparencyLevel TransparencyLevel { get; private set; }
+
         public IPopupImpl CreatePopup() => null;
     }
 }

src/Avalonia.Controls/Expander.cs

@@ -78,17 +78,13 @@ namespace Avalonia.Controls
             }
         }
 
-        protected override void OnPropertyChanged<T>(
+        protected override void OnPropertyChanged<T>(AvaloniaPropertyChangedEventArgs<T> change)
-            AvaloniaProperty<T> property,
-            Optional<T> oldValue,
-            BindingValue<T> newValue,
-            BindingPriority priority)
         {
-            base.OnPropertyChanged(property, oldValue, newValue, priority);
+            base.OnPropertyChanged(change);
 
-            if (property == ExpandDirectionProperty)
+            if (change.Property == ExpandDirectionProperty)
             {
-                UpdatePseudoClasses(newValue.GetValueOrDefault<ExpandDirection>());
+                UpdatePseudoClasses(change.NewValue.GetValueOrDefault<ExpandDirection>());
             }
         }
 

src/Avalonia.Controls/Grid.cs

@@ -1228,7 +1228,7 @@ namespace Avalonia.Controls
             Debug.Assert(1 < count && 0 <= start && (start + count) <= definitions.Count);
 
             //  avoid processing when asked to distribute "0"
-            if (!_IsZero(requestedSize))
+            if (!MathUtilities.IsZero(requestedSize))
             {
                 DefinitionBase[] tempDefinitions = TempDefinitions; //  temp array used to remember definitions for sorting
                 int end = start + count;
@@ -1306,7 +1306,7 @@ namespace Avalonia.Controls
                         }
 
                         //  sanity check: requested size must all be distributed
-                        Debug.Assert(_IsZero(sizeToDistribute));
+                        Debug.Assert(MathUtilities.IsZero(sizeToDistribute));
                     }
                     else if (requestedSize <= rangeMaxSize)
                     {
@@ -1346,7 +1346,7 @@ namespace Avalonia.Controls
                         }
 
                         //  sanity check: requested size must all be distributed
-                        Debug.Assert(_IsZero(sizeToDistribute));
+                        Debug.Assert(MathUtilities.IsZero(sizeToDistribute));
                     }
                     else
                     {
@@ -1358,7 +1358,7 @@ namespace Avalonia.Controls
                         double equalSize = requestedSize / count;
 
                         if (equalSize < maxMaxSize
-                            && !_AreClose(equalSize, maxMaxSize))
+                            && !MathUtilities.AreClose(equalSize, maxMaxSize))
                         {
                             //  equi-size is less than maximum of maxSizes.
                             //  in this case distribute so that smaller definitions grow faster than
@@ -2151,7 +2151,7 @@ namespace Avalonia.Controls
                 // and precision of floating-point computation.  (However, the resulting
                 // display is subject to anti-aliasing problems.   TANSTAAFL.)
 
-                if (!_AreClose(roundedTakenSize, finalSize))
+                if (!MathUtilities.AreClose(roundedTakenSize, finalSize))
                 {
                     // Compute deltas
                     for (int i = 0; i < definitions.Count; ++i)
@@ -2168,7 +2168,7 @@ namespace Avalonia.Controls
                     if (roundedTakenSize > finalSize)
                     {
                         int i = definitions.Count - 1;
-                        while ((adjustedSize > finalSize && !_AreClose(adjustedSize, finalSize)) && i >= 0)
+                        while ((adjustedSize > finalSize && !MathUtilities.AreClose(adjustedSize, finalSize)) && i >= 0)
                         {
                             DefinitionBase definition = definitions[definitionIndices[i]];
                             double final = definition.SizeCache - dpiIncrement;
@@ -2184,7 +2184,7 @@ namespace Avalonia.Controls
                     else if (roundedTakenSize < finalSize)
                     {
                         int i = 0;
-                        while ((adjustedSize < finalSize && !_AreClose(adjustedSize, finalSize)) && i < definitions.Count)
+                        while ((adjustedSize < finalSize && !MathUtilities.AreClose(adjustedSize, finalSize)) && i < definitions.Count)
                         {
                             DefinitionBase definition = definitions[definitionIndices[i]];
                             double final = definition.SizeCache + dpiIncrement;
@@ -2595,27 +2595,6 @@ namespace Avalonia.Controls
             set { SetFlags(value, Flags.HasGroup3CellsInAutoRows); }
         }
 
-        /// <summary>
-        /// fp version of <c>d == 0</c>.
-        /// </summary>
-        /// <param name="d">Value to check.</param>
-        /// <returns><c>true</c> if d == 0.</returns>
-        private static bool _IsZero(double d)
-        {
-            return (Math.Abs(d) < double.Epsilon);
-        }
-
-        /// <summary>
-        /// fp version of <c>d1 == d2</c>
-        /// </summary>
-        /// <param name="d1">First value to compare</param>
-        /// <param name="d2">Second value to compare</param>
-        /// <returns><c>true</c> if d1 == d2</returns>
-        private static bool _AreClose(double d1, double d2)
-        {
-            return (Math.Abs(d1 - d2) < double.Epsilon);
-        }
-
         /// <summary>
         /// Returns reference to extended data bag.
         /// </summary>

src/Avalonia.Controls/IndexPath.cs

@@ -123,6 +123,26 @@ namespace Avalonia.Controls
             }
         }
 
+        public bool IsAncestorOf(in IndexPath other)
+        {
+            if (other.GetSize() <= GetSize())
+            {
+                return false;
+            }
+
+            var size = GetSize();
+
+            for (int i = 0; i < size; i++)
+            {
+                if (GetAt(i) != other.GetAt(i))
+                {
+                    return false;
+                }
+            }
+
+            return true;
+        }
+
         public override string ToString()
         {
             if (_path != null)

src/Avalonia.Controls/IndexRange.cs

@@ -132,6 +132,53 @@ namespace Avalonia.Controls
             return result;
         }
 
+        public static int Intersect(
+            IList<IndexRange> ranges,
+            IndexRange range,
+            IList<IndexRange>? removed = null)
+        {
+            var result = 0;
+
+            for (var i = 0; i < ranges.Count && range != s_invalid; ++i)
+            {
+                var existing = ranges[i];
+
+                if (existing.End < range.Begin || existing.Begin > range.End)
+                {
+                    removed?.Add(existing);
+                    ranges.RemoveAt(i--);
+                    result += existing.Count;
+                }
+                else
+                {
+                    if (existing.Begin < range.Begin)
+                    {
+                        var except = new IndexRange(existing.Begin, range.Begin - 1);
+                        removed?.Add(except);
+                        ranges[i] = existing = new IndexRange(range.Begin, existing.End);
+                        result += except.Count;
+                    }
+
+                    if (existing.End > range.End)
+                    {
+                        var except = new IndexRange(range.End + 1, existing.End);
+                        removed?.Add(except);
+                        ranges[i] = new IndexRange(existing.Begin, range.End);
+                        result += except.Count;
+                    }
+                }
+            }
+
+            MergeRanges(ranges);
+
+            if (removed is object)
+            {
+                MergeRanges(removed);
+            }
+
+            return result;
+        }
+
         public static int Remove(
             IList<IndexRange> ranges,
             IndexRange range,

src/Avalonia.Controls/LayoutTransformControl.cs

@@ -14,8 +14,8 @@ namespace Avalonia.Controls
     /// </summary>
     public class LayoutTransformControl : Decorator
     {
-        public static readonly StyledProperty<Transform> LayoutTransformProperty =
+        public static readonly StyledProperty<ITransform> LayoutTransformProperty =
-            AvaloniaProperty.Register<LayoutTransformControl, Transform>(nameof(LayoutTransform));
+            AvaloniaProperty.Register<LayoutTransformControl, ITransform>(nameof(LayoutTransform));
 
         public static readonly StyledProperty<bool> UseRenderTransformProperty =
             AvaloniaProperty.Register<LayoutTransformControl, bool>(nameof(LayoutTransform));
@@ -37,7 +37,7 @@ namespace Avalonia.Controls
         /// <summary>
         /// Gets or sets a graphics transformation that should apply to this element when layout is performed.
         /// </summary>
-        public Transform LayoutTransform
+        public ITransform LayoutTransform
         {
             get { return GetValue(LayoutTransformProperty); }
             set { SetValue(LayoutTransformProperty, value); }