Merge branch 'master' into fixes/3094-focusable-hang

build/Base.props

@@ -1,5 +1,6 @@
 <Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <ItemGroup>
     <PackageReference Include="System.ValueTuple" Version="4.5.0" />
+    <PackageReference Include="System.Runtime.CompilerServices.Unsafe" Version="4.6.0" />
   </ItemGroup>
 </Project>

src/Avalonia.Visuals/Rendering/SceneGraph/SceneBuilder.cs

@@ -148,6 +148,19 @@ namespace Avalonia.Rendering.SceneGraph
             return (VisualNode)node;
         }
 
+        private static object GetOrCreateChildNode(Scene scene, IVisual child, VisualNode parent)
+        {
+            var result = (VisualNode)scene.FindNode(child);
+
+            if (result != null && result.Parent != parent)
+            {
+                Deindex(scene, result);
+                result = null;
+            }
+
+            return result ?? CreateNode(scene, child, parent);
+        }
+
         private static void Update(DrawingContext context, Scene scene, VisualNode node, Rect clip, bool forceRecurse)
         {
             var visual = node.Visual;
@@ -231,7 +244,7 @@ namespace Avalonia.Rendering.SceneGraph
                     {
                         foreach (var child in visual.VisualChildren.OrderBy(x => x, ZIndexComparer.Instance))
                         {
-                            var childNode = scene.FindNode(child) ?? CreateNode(scene, child, node);
+                            var childNode = GetOrCreateChildNode(scene, child, node);
                             Update(context, scene, (VisualNode)childNode, clip, forceRecurse);
                         }
 

src/Avalonia.Visuals/Rendering/SceneGraph/VisualNode.cs

@@ -119,6 +119,11 @@ namespace Avalonia.Rendering.SceneGraph
                 throw new ObjectDisposedException("Visual node for {node.Visual}");
             }
 
+            if (child.Parent != this)
+            {
+                throw new AvaloniaInternalException("VisualNode added to wrong parent.");
+            }
+
             EnsureChildrenCreated();
             _children.Add(child);
         }
@@ -155,6 +160,11 @@ namespace Avalonia.Rendering.SceneGraph
                 throw new ObjectDisposedException("Visual node for {node.Visual}");
             }
 
+            if (node.Parent != this)
+            {
+                throw new AvaloniaInternalException("VisualNode added to wrong parent.");
+            }
+
             EnsureChildrenCreated();
             _children[index] = node;
         }

src/Windows/Avalonia.Win32/Interop/UnmanagedMethods.cs

@@ -1031,6 +1031,9 @@ namespace Avalonia.Win32.Interop
         [DllImport("shcore.dll")]
         public static extern long GetDpiForMonitor(IntPtr hmonitor, MONITOR_DPI_TYPE dpiType, out uint dpiX, out uint dpiY);
 
+        [DllImport("gdi32.dll")]
+        public static extern int GetDeviceCaps(IntPtr hdc, DEVICECAP nIndex);
+
         [DllImport("shcore.dll")]
         public static extern void GetScaleFactorForMonitor(IntPtr hMon, out uint pScale);
 
@@ -1147,6 +1150,12 @@ namespace Avalonia.Win32.Interop
             }
         }
 
+        public enum DEVICECAP
+        {
+            HORZRES = 8,
+            DESKTOPHORZRES = 118
+        }
+
         public enum PROCESS_DPI_AWARENESS
         {
             PROCESS_DPI_UNAWARE = 0,

src/Windows/Avalonia.Win32/ScreenImpl.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using Avalonia.Platform;
+using Avalonia.Win32.Interop;
 using static Avalonia.Win32.Interop.UnmanagedMethods;
 
 namespace Avalonia.Win32
@@ -28,9 +29,28 @@ namespace Avalonia.Win32
                         (IntPtr monitor, IntPtr hdcMonitor, ref Rect lprcMonitor, IntPtr data) =>
                         {
                             MONITORINFO monitorInfo = MONITORINFO.Create();
-                            if (GetMonitorInfo(monitor,ref monitorInfo))
+                            if (GetMonitorInfo(monitor, ref monitorInfo))
                             {
-                                GetDpiForMonitor(monitor, MONITOR_DPI_TYPE.MDT_EFFECTIVE_DPI, out var x, out _);
+                                var dpi = 1.0;
+
+                                var shcore = LoadLibrary("shcore.dll");
+                                var method = GetProcAddress(shcore, nameof(GetDpiForMonitor));
+                                if (method != IntPtr.Zero)
+                                { 
+                                    GetDpiForMonitor(monitor, MONITOR_DPI_TYPE.MDT_EFFECTIVE_DPI, out var x, out _);
+                                    dpi = (double)x;
+                                }
+                                else
+                                {
+                                    var hdc = GetDC(IntPtr.Zero);
+
+                                    double virtW = GetDeviceCaps(hdc, DEVICECAP.HORZRES);
+                                    double physW = GetDeviceCaps(hdc, DEVICECAP.DESKTOPHORZRES);
+
+                                    dpi = (96d * physW / virtW);
+
+                                    ReleaseDC(IntPtr.Zero, hdc);
+                                }
 
                                 RECT bounds = monitorInfo.rcMonitor;
                                 RECT workingArea = monitorInfo.rcWork;
@@ -40,7 +60,7 @@ namespace Avalonia.Win32
                                     new PixelRect(workingArea.left, workingArea.top, workingArea.right - workingArea.left,
                                         workingArea.bottom - workingArea.top);
                                 screens[index] =
-                                    new WinScreen((double)x / 96.0d, avaloniaBounds, avaloniaWorkArea, monitorInfo.dwFlags == 1,
+                                    new WinScreen(dpi / 96.0d, avaloniaBounds, avaloniaWorkArea, monitorInfo.dwFlags == 1,
                                         monitor);
                                 index++;
                             }

tests/Avalonia.Visuals.UnitTests/Rendering/SceneGraph/DeferredDrawingContextImplTests.cs

@@ -17,7 +17,7 @@ namespace Avalonia.Visuals.UnitTests.Rendering.SceneGraph
         public void Should_Add_VisualNode()
         {
             var parent = new VisualNode(new TestRoot(), null);
-            var child = new VisualNode(Mock.Of<IVisual>(), null);
+            var child = new VisualNode(Mock.Of<IVisual>(), parent);
             var layers = new SceneLayers(parent.Visual);
             var target = new DeferredDrawingContextImpl(null, layers);
 
@@ -32,7 +32,7 @@ namespace Avalonia.Visuals.UnitTests.Rendering.SceneGraph
         public void Should_Not_Replace_Identical_VisualNode()
         {
             var parent = new VisualNode(new TestRoot(), null);
-            var child = new VisualNode(Mock.Of<IVisual>(), null);
+            var child = new VisualNode(Mock.Of<IVisual>(), parent);
             var layers = new SceneLayers(parent.Visual);
 
             parent.AddChild(child);
@@ -50,8 +50,8 @@ namespace Avalonia.Visuals.UnitTests.Rendering.SceneGraph
         public void Should_Replace_Different_VisualNode()
         {
             var parent = new VisualNode(new TestRoot(), null);
-            var child1 = new VisualNode(Mock.Of<IVisual>(), null);
-            var child2 = new VisualNode(Mock.Of<IVisual>(), null);
+            var child1 = new VisualNode(Mock.Of<IVisual>(), parent);
+            var child2 = new VisualNode(Mock.Of<IVisual>(), parent);
             var layers = new SceneLayers(parent.Visual);
 
             parent.AddChild(child1);
@@ -78,8 +78,8 @@ namespace Avalonia.Visuals.UnitTests.Rendering.SceneGraph
 
             var layers = new SceneLayers(root);
             var target = new DeferredDrawingContextImpl(null, layers);
-            var child1 = new VisualNode(Mock.Of<IVisual>(), null) { LayerRoot = root };
-            var child2 = new VisualNode(Mock.Of<IVisual>(), null) { LayerRoot = root };
+            var child1 = new VisualNode(Mock.Of<IVisual>(), node) { LayerRoot = root };
+            var child2 = new VisualNode(Mock.Of<IVisual>(), node) { LayerRoot = root };
 
             target.BeginUpdate(node);
             using (target.BeginUpdate(child1)) { }

tests/Avalonia.Visuals.UnitTests/Rendering/SceneGraph/SceneBuilderTests.cs

@@ -620,10 +620,9 @@ namespace Avalonia.Visuals.UnitTests.Rendering.SceneGraph
                 border1.IsVisible = false;
 
                 scene = scene.CloneScene();
-
-                var panelNode = (VisualNode)scene.FindNode(panel);
                 sceneBuilder.Update(scene, decorator);
 
+                var panelNode = (VisualNode)scene.FindNode(panel);
                 Assert.Equal(2, panelNode.Children.Count);
                 Assert.False(panelNode.Children[0].Disposed);
                 Assert.False(panelNode.Children[1].Disposed);

tests/Avalonia.Visuals.UnitTests/Rendering/SceneGraph/VisualNodeTests.cs

@@ -24,7 +24,7 @@ namespace Avalonia.Visuals.UnitTests.Rendering.SceneGraph
             var node = new VisualNode(Mock.Of<IVisual>(), null);
             var collection = node.Children;
 
-            node.AddChild(Mock.Of<IVisualNode>());
+            node.AddChild(Mock.Of<IVisualNode>(x => x.Parent == node));
 
             Assert.NotSame(collection, node.Children);
         }
@@ -106,9 +106,9 @@ namespace Avalonia.Visuals.UnitTests.Rendering.SceneGraph
         public void TrimChildren_Should_Work_Correctly()
         {
             var parent = new VisualNode(Mock.Of<IVisual>(), null);
-            var child1 = new VisualNode(Mock.Of<IVisual>(), null);
-            var child2 = new VisualNode(Mock.Of<IVisual>(), null);
-            var child3 = new VisualNode(Mock.Of<IVisual>(), null);
+            var child1 = new VisualNode(Mock.Of<IVisual>(), parent);
+            var child2 = new VisualNode(Mock.Of<IVisual>(), parent);
+            var child3 = new VisualNode(Mock.Of<IVisual>(), parent);
 
             parent.AddChild(child1);
             parent.AddChild(child2);