Merge remote-tracking branch 'origin/master' into feature/fluent-slider-template

src/Avalonia.Controls/Platform/IPopupImpl.cs

@@ -8,5 +8,7 @@ namespace Avalonia.Platform
     public interface IPopupImpl : IWindowBaseImpl
     {
         IPopupPositioner PopupPositioner { get; }
+
+        void SetWindowManagerAddShadowHint(bool enabled);
     }
 }

src/Avalonia.Controls/Primitives/Popup.cs

@@ -19,6 +19,9 @@ namespace Avalonia.Controls.Primitives
     /// </summary>
     public class Popup : Control, IVisualTreeHost
     {
+        public static readonly StyledProperty<bool> WindowManagerAddShadowHintProperty =
+            AvaloniaProperty.Register<PopupRoot, bool>(nameof(WindowManagerAddShadowHint), true);
+
         /// <summary>
         /// Defines the <see cref="Child"/> property.
         /// </summary>
@@ -89,7 +92,7 @@ namespace Avalonia.Controls.Primitives
         {
             IsHitTestVisibleProperty.OverrideDefaultValue<Popup>(false);
             ChildProperty.Changed.AddClassHandler<Popup>((x, e) => x.ChildChanged(e));
-            IsOpenProperty.Changed.AddClassHandler<Popup>((x, e) => x.IsOpenChanged((AvaloniaPropertyChangedEventArgs<bool>)e));
+            IsOpenProperty.Changed.AddClassHandler<Popup>((x, e) => x.IsOpenChanged((AvaloniaPropertyChangedEventArgs<bool>)e));            
         }
 
         /// <summary>
@@ -104,6 +107,12 @@ namespace Avalonia.Controls.Primitives
 
         public IPopupHost? Host => _openState?.PopupHost;
 
+        public bool WindowManagerAddShadowHint
+        {
+            get { return GetValue(WindowManagerAddShadowHintProperty); }
+            set { SetValue(WindowManagerAddShadowHintProperty, value); }
+        }
+
         /// <summary>
         /// Gets or sets the control to display in the popup.
         /// </summary>
@@ -293,6 +302,8 @@ namespace Avalonia.Controls.Primitives
 
             _openState = new PopupOpenState(topLevel, popupHost, cleanupPopup);
 
+            WindowManagerAddShadowHintChanged(popupHost, WindowManagerAddShadowHint);
+
             popupHost.Show();
 
             using (BeginIgnoringIsOpen())
@@ -332,6 +343,14 @@ namespace Avalonia.Controls.Primitives
             return Disposable.Create((unsubscribe, target, handler), state => state.unsubscribe(state.target, state.handler));
         }
 
+        private void WindowManagerAddShadowHintChanged(IPopupHost host, bool hint)
+        {
+            if(host is PopupRoot pr)
+            {
+                pr.PlatformImpl.SetWindowManagerAddShadowHint(hint);
+            }
+        }
+
         /// <summary>
         /// Called when the <see cref="IsOpen"/> property changes.
         /// </summary>

src/Avalonia.Controls/Primitives/PopupRoot.cs

@@ -17,14 +17,14 @@ namespace Avalonia.Controls.Primitives
     public sealed class PopupRoot : WindowBase, IInteractive, IHostedVisualTreeRoot, IDisposable, IStyleHost, IPopupHost
     {
         private readonly TopLevel _parent;
-        private PopupPositionerParameters _positionerParameters;
+        private PopupPositionerParameters _positionerParameters;        
 
         /// <summary>
         /// Initializes static members of the <see cref="PopupRoot"/> class.
         /// </summary>
         static PopupRoot()
         {
-            BackgroundProperty.OverrideDefaultValue(typeof(PopupRoot), Brushes.White);
+            BackgroundProperty.OverrideDefaultValue(typeof(PopupRoot), Brushes.White);            
         }
 
         /// <summary>
@@ -53,7 +53,7 @@ namespace Avalonia.Controls.Primitives
         /// Gets the platform-specific window implementation.
         /// </summary>
         [CanBeNull]
-        public new IPopupImpl PlatformImpl => (IPopupImpl)base.PlatformImpl;
+        public new IPopupImpl PlatformImpl => (IPopupImpl)base.PlatformImpl;               
 
         /// <summary>
         /// Gets the parent control in the event route.

src/Avalonia.Controls/Utils/BorderRenderHelper.cs

@@ -118,12 +118,11 @@ namespace Avalonia.Controls.Utils
                     pen = new Pen(borderBrush, borderThickness);
                 }
 
-                var rrect = new RoundedRect(new Rect(_size), _cornerRadius.TopLeft, _cornerRadius.TopRight,
-                    _cornerRadius.BottomRight, _cornerRadius.BottomLeft);
+                var rect = new Rect(_size);
                 if (Math.Abs(borderThickness) > double.Epsilon)
-                {
-                    rrect = rrect.Deflate(borderThickness * 0.5, borderThickness * 0.5);
-                }
+                    rect = rect.Deflate(borderThickness * 0.5);
+                var rrect = new RoundedRect(rect, _cornerRadius.TopLeft, _cornerRadius.TopRight,
+                    _cornerRadius.BottomRight, _cornerRadius.BottomLeft);
 
                 context.PlatformImpl.DrawRectangle(background, pen, rrect, boxShadows);
             }

src/Avalonia.DesignerSupport/Remote/Stubs.cs

@@ -146,6 +146,10 @@ namespace Avalonia.DesignerSupport.Remote
 
         public void SetTransparencyLevelHint(WindowTransparencyLevel transparencyLevel) { }
 
+        public void SetWindowManagerAddShadowHint(bool enabled)
+        {
+        }
+
         public WindowTransparencyLevel TransparencyLevel { get; private set; }
     }
 

src/Avalonia.Native/PopupImpl.cs

@@ -59,6 +59,11 @@ namespace Avalonia.Native
         }
 
         public override IPopupImpl CreatePopup() => new PopupImpl(_factory, _opts, _glFeature, this);
+
+        public void SetWindowManagerAddShadowHint(bool enabled)
+        {
+        }
+
         public IPopupPositioner PopupPositioner { get; }
     }
 }

src/Avalonia.Themes.Fluent/Accents/BaseDark.xaml

@@ -139,6 +139,7 @@
     <SolidColorBrush x:Key="SystemControlErrorTextForegroundBrush" Color="{StaticResource SystemErrorTextColor}" />
     <SolidColorBrush x:Key="SystemControlTransientBorderBrush" Color="#000000" Opacity="0.36" />
     <!--<AcrylicBrush x:Key="SystemControlTransientBackgroundBrush" BackgroundSource="HostBackdrop" TintColor="{StaticResource SystemChromeAltHighColor}" TintOpacity="0.8" FallbackColor="{StaticResource SystemChromeMediumLowColor}" />-->
+    <SolidColorBrush x:Key="SystemControlTransientBackgroundBrush" Color="{StaticResource SystemChromeMediumLowColor}" />
     <StaticResource x:Key="SystemControlDescriptionTextForegroundBrush" ResourceKey="SystemControlPageTextBaseMediumBrush" />
     <x:Boolean x:Key="IsApplicationFocusVisualKindReveal">False</x:Boolean>
 
@@ -159,8 +160,7 @@
     <x:Double x:Key="AppBarThemeMinimalHeight">24</x:Double>
     <x:Double x:Key="AppBarThemeCompactHeight">40</x:Double>
     <x:Double x:Key="AppBarExpandButtonCircleDiameter">3</x:Double>
-    <x:Double x:Key="AutoSuggestListMaxHeight">374</x:Double>
-    <x:Double x:Key="AutoSuggestListBorderOpacity">0</x:Double>
+    <x:Double x:Key="AutoCompleteListBorderOpacity">0</x:Double>
     <Thickness x:Key="CheckBoxBorderThemeThickness">2</Thickness>
     <Thickness x:Key="CheckBoxCheckedStrokeThickness">0</Thickness>
     <x:Double x:Key="ComboBoxArrowThemeFontSize">21</x:Double>
@@ -258,10 +258,10 @@
     <Thickness x:Key="AppBarTopBorderThemeThickness">0,0,0,0</Thickness>
     <Thickness x:Key="AppBarTopThemePadding">0,0,0,0</Thickness>
     <Thickness x:Key="AppBarExpandButtonCircleInnerPadding">3,0,3,0</Thickness>
-    <Thickness x:Key="AutoSuggestListBorderThemeThickness">1</Thickness>
-    <Thickness x:Key="AutoSuggestListMargin">0,2,0,2</Thickness>
-    <Thickness x:Key="AutoSuggestListPadding">-1,0,-1,0</Thickness>
-    <Thickness x:Key="AutoSuggestListViewItemMargin">12,11,0,13</Thickness>
+    <Thickness x:Key="AutoCompleteListBorderThemeThickness">1</Thickness>
+    <Thickness x:Key="AutoCompleteListMargin">0,2,0,2</Thickness>
+    <Thickness x:Key="AutoCompleteListPadding">-1,0,-1,0</Thickness>
+    <Thickness x:Key="AutoCompleteListViewItemMargin">12,11,0,13</Thickness>
     <Thickness x:Key="ButtonBorderThemeThickness">2</Thickness>
     <Thickness x:Key="CalendarDatePickerBorderThemeThickness">2</Thickness>
     <Thickness x:Key="ComboBoxBorderThemeThickness">2</Thickness>

src/Avalonia.Themes.Fluent/Accents/BaseLight.xaml

@@ -139,6 +139,7 @@
     <SolidColorBrush x:Key="SystemControlErrorTextForegroundBrush" Color="{StaticResource SystemErrorTextColor}" />
     <SolidColorBrush x:Key="SystemControlTransientBorderBrush" Color="#000000" Opacity="0.14" />
     <!--<AcrylicBrush x:Key="SystemControlTransientBackgroundBrush" BackgroundSource="HostBackdrop" TintColor="{StaticResource SystemChromeAltHighColor}" TintOpacity="0.8" FallbackColor="{StaticResource SystemChromeMediumLowColor}" />-->
+    <SolidColorBrush x:Key="SystemControlTransientBackgroundBrush" Color="{StaticResource SystemChromeMediumLowColor}" />
     <StaticResource x:Key="SystemControlDescriptionTextForegroundBrush" ResourceKey="SystemControlPageTextBaseMediumBrush" />
     <x:Boolean x:Key="IsApplicationFocusVisualKindReveal">False</x:Boolean>
 
@@ -158,8 +159,7 @@
     <x:Double x:Key="AppBarThemeMinimalHeight">24</x:Double>
     <x:Double x:Key="AppBarThemeCompactHeight">40</x:Double>
     <x:Double x:Key="AppBarExpandButtonCircleDiameter">3</x:Double>
-    <x:Double x:Key="AutoSuggestListMaxHeight">374</x:Double>
-    <x:Double x:Key="AutoSuggestListBorderOpacity">0</x:Double>
+    <x:Double x:Key="AutoCompleteListBorderOpacity">0</x:Double>
     <Thickness x:Key="CheckBoxBorderThemeThickness">2</Thickness>
     <Thickness x:Key="CheckBoxCheckedStrokeThickness">0</Thickness>
     <x:Double x:Key="ComboBoxArrowThemeFontSize">21</x:Double>
@@ -257,10 +257,10 @@
     <Thickness x:Key="AppBarTopBorderThemeThickness">0,0,0,0</Thickness>
     <Thickness x:Key="AppBarTopThemePadding">0,0,0,0</Thickness>
     <Thickness x:Key="AppBarExpandButtonCircleInnerPadding">3,0,3,0</Thickness>
-    <Thickness x:Key="AutoSuggestListBorderThemeThickness">1</Thickness>
-    <Thickness x:Key="AutoSuggestListMargin">0,2,0,2</Thickness>
-    <Thickness x:Key="AutoSuggestListPadding">-1,0,-1,0</Thickness>
-    <Thickness x:Key="AutoSuggestListViewItemMargin">12,11,0,13</Thickness>
+    <Thickness x:Key="AutoCompleteListBorderThemeThickness">1</Thickness>
+    <Thickness x:Key="AutoCompleteListMargin">0,2,0,2</Thickness>
+    <Thickness x:Key="AutoCompleteListPadding">-1,0,-1,0</Thickness>
+    <Thickness x:Key="AutoCompleteListViewItemMargin">12,11,0,13</Thickness>
     <Thickness x:Key="ButtonBorderThemeThickness">2</Thickness>
     <Thickness x:Key="CalendarDatePickerBorderThemeThickness">2</Thickness>
     <Thickness x:Key="ComboBoxBorderThemeThickness">2</Thickness>

src/Avalonia.Themes.Fluent/Accents/FluentBaseDark.xaml

@@ -137,7 +137,13 @@
     <StaticResource x:Key="TextControlButtonForegroundPressed" ResourceKey="SystemControlHighlightAltChromeWhiteBrush" />
     <StaticResource x:Key="ContentLinkForegroundColor" ResourceKey="SystemControlHyperlinkTextBrush" />
     <StaticResource x:Key="ContentLinkBackgroundColor" ResourceKey="SystemControlPageBackgroundChromeLowBrush" />
-    
+
+    <!-- Resources for AutoCompleteBox.xaml -->
+    <StaticResource x:Key="AutoCompleteBoxLightDismissOverlayBackground" ResourceKey="SystemControlPageBackgroundMediumAltMediumBrush" />
+    <StaticResource x:Key="AutoCompleteBoxSuggestionsListBackground" ResourceKey="SystemControlBackgroundChromeMediumLowBrush" />
+    <StaticResource x:Key="AutoCompleteBoxSuggestionsListBorderBrush" ResourceKey="SystemControlForegroundChromeHighBrush" />
+    <x:Double x:Key="AutoCompleteBoxIconFontSize">12</x:Double>
+
     <!-- BaseResources for CheckBox.xaml -->
     <StaticResource x:Key="CheckBoxForegroundUnchecked" ResourceKey="SystemControlForegroundBaseHighBrush" />
     <StaticResource x:Key="CheckBoxForegroundUncheckedPointerOver" ResourceKey="SystemControlForegroundBaseHighBrush" />

src/Avalonia.Themes.Fluent/Accents/FluentBaseLight.xaml

@@ -137,7 +137,13 @@
     <StaticResource x:Key="TextControlButtonForegroundPressed" ResourceKey="SystemControlHighlightAltChromeWhiteBrush" />
     <StaticResource x:Key="ContentLinkForegroundColor" ResourceKey="SystemControlHyperlinkTextBrush" />
     <StaticResource x:Key="ContentLinkBackgroundColor" ResourceKey="SystemControlPageBackgroundChromeLowBrush" />
-    
+
+    <!-- Resources for AutoCompleteBox.xaml -->
+    <StaticResource x:Key="AutoCompleteBoxLightDismissOverlayBackground" ResourceKey="SystemControlPageBackgroundMediumAltMediumBrush" />
+    <StaticResource x:Key="AutoCompleteBoxSuggestionsListBackground" ResourceKey="SystemControlBackgroundChromeMediumLowBrush" />
+    <StaticResource x:Key="AutoCompleteBoxSuggestionsListBorderBrush" ResourceKey="SystemControlForegroundChromeHighBrush" />
+    <x:Double x:Key="AutoCompleteBoxIconFontSize">12</x:Double>
+
     <!-- BaseResources for CheckBox.xaml -->
     <StaticResource x:Key="CheckBoxForegroundUnchecked" ResourceKey="SystemControlForegroundBaseHighBrush" />
     <StaticResource x:Key="CheckBoxForegroundUncheckedPointerOver" ResourceKey="SystemControlForegroundBaseHighBrush" />

src/Avalonia.Themes.Fluent/Accents/FluentControlResourcesDark.xaml

@@ -82,6 +82,12 @@
     <StaticResource x:Key="TextControlForegroundFocused" ResourceKey="SystemControlForegroundBaseHighBrush" />
     <StaticResource x:Key="TextControlPlaceholderForegroundFocused" ResourceKey="SystemControlForegroundBaseMediumLowBrush" />
 
+    <!-- Resources for AutoCompleteBox.xaml -->
+    <StaticResource x:Key="AutoCompleteBoxSuggestionsListBackground" ResourceKey="SystemControlTransientBackgroundBrush" />
+    <StaticResource x:Key="AutoCompleteBoxSuggestionsListBorderBrush" ResourceKey="SystemControlTransientBorderBrush" />
+    <StaticResource x:Key="AutoCompleteBoxLightDismissOverlayBackground" ResourceKey="SystemControlPageBackgroundMediumAltMediumBrush" />
+    <x:Double x:Key="AutoCompleteBoxIconFontSize">12</x:Double>
+
     <!-- Resources for Checkbox.xaml -->
     <Thickness x:Key="CheckBoxBorderThemeThickness">1</Thickness>
     <Thickness x:Key="CheckBoxCheckedStrokeThickness">0</Thickness>

src/Avalonia.Themes.Fluent/Accents/FluentControlResourcesLight.xaml

@@ -82,6 +82,12 @@
     <StaticResource x:Key="TextControlForegroundFocused" ResourceKey="SystemControlForegroundBaseHighBrush" />
     <StaticResource x:Key="TextControlPlaceholderForegroundFocused" ResourceKey="SystemControlForegroundBaseMediumLowBrush" />
 
+    <!-- Resources for AutoCompleteBox.xaml -->
+    <StaticResource x:Key="AutoCompleteBoxSuggestionsListBackground" ResourceKey="SystemControlTransientBackgroundBrush" />
+    <StaticResource x:Key="AutoCompleteBoxSuggestionsListBorderBrush" ResourceKey="SystemControlTransientBorderBrush" />
+    <StaticResource x:Key="AutoCompleteBoxLightDismissOverlayBackground" ResourceKey="SystemControlPageBackgroundMediumAltMediumBrush" />
+    <x:Double x:Key="AutoCompleteBoxIconFontSize">12</x:Double>
+
     <!-- Resources for CheckBox.xaml -->
     <x:Double x:Key="CheckBoxBorderThemeThickness">1</x:Double>
     <x:Double x:Key="CheckBoxCheckedStrokeThickness">0</x:Double>

src/Avalonia.Themes.Fluent/AutoCompleteBox.xaml

@@ -1,37 +1,69 @@
-<Styles xmlns="https://github.com/avaloniaui">
+<Styles xmlns="https://github.com/avaloniaui" 
+        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
+  <Design.PreviewWith>
+    <Border Padding="20">
+      <AutoCompleteBox Width="200">
+        <AutoCompleteBox.Items>
+          Alabama
+          Alaska
+          Arizona
+          Arkansas
+          California
+          Colorado
+          Connecticut
+          Delaware
+        </AutoCompleteBox.Items>
+      </AutoCompleteBox>
+    </Border>
+  </Design.PreviewWith>
+
   <Style Selector="AutoCompleteBox">
-    <Setter Property="Background" Value="{DynamicResource ThemeBackgroundBrush}"/>
-    <Setter Property="BorderBrush" Value="{DynamicResource ThemeBorderMidBrush}"/>
-    <Setter Property="BorderThickness" Value="{DynamicResource ThemeBorderThickness}"/>
-    <Setter Property="Padding" Value="4"/>
+    <Setter Property="VerticalAlignment" Value="Top" />
+    <Setter Property="Foreground" Value="{DynamicResource TextControlForeground}" />
+    <Setter Property="Background" Value="{DynamicResource TextControlBackground}" />
+    <Setter Property="BorderBrush" Value="{DynamicResource TextControlBorderBrush}" />
+    <Setter Property="BorderThickness" Value="{DynamicResource TextControlBorderThemeThickness}" />
+    <Setter Property="FontFamily" Value="{DynamicResource ContentControlThemeFontFamily}" />
+    <Setter Property="FontSize" Value="{DynamicResource ControlContentThemeFontSize}" />
+    <Setter Property="Padding" Value="{DynamicResource TextControlThemePadding}" />
     <Setter Property="Template">
       <ControlTemplate>
-        <Panel>
+        <Grid Name="PART_LayoutRoot">
           <TextBox Name="PART_TextBox"
-                   Background="{TemplateBinding Background}" 
-                   BorderBrush="{TemplateBinding BorderBrush}" 
+                   Watermark="{TemplateBinding Watermark}"
+                   Width="{TemplateBinding Width}"
+                   Foreground="{TemplateBinding Foreground}"
+                   Background="{TemplateBinding Background}"
+                   BorderBrush="{TemplateBinding BorderBrush}"
                    BorderThickness="{TemplateBinding BorderThickness}"
+                   FontSize="{TemplateBinding FontSize}"
+                   FontFamily="{TemplateBinding FontFamily}"
+                   FontWeight="{TemplateBinding FontWeight}"
                    Padding="{TemplateBinding Padding}"
-                   Watermark="{TemplateBinding Watermark}"
+                   Margin="0"
                    DataValidationErrors.Errors="{TemplateBinding (DataValidationErrors.Errors)}" />
           
           <Popup Name="PART_Popup"
+                 WindowManagerAddShadowHint="False"
                  MinWidth="{Binding Bounds.Width, RelativeSource={RelativeSource TemplatedParent}}"
                  MaxHeight="{TemplateBinding MaxDropDownHeight}"
-                 PlacementTarget="{TemplateBinding}"
-                 StaysOpen="False">
-            <Border BorderBrush="{DynamicResource ThemeBorderMidBrush}"
-                    BorderThickness="1">
+                 StaysOpen="False"                 
+                 PlacementTarget="{TemplateBinding}">            
+            <Border Name="PART_SuggestionsContainer"
+                    Padding="{DynamicResource AutoCompleteListMargin}"
+                    BorderThickness="{DynamicResource AutoCompleteListBorderThemeThickness}"
+                    BorderBrush="{DynamicResource AutoSuggestBoxSuggestionsListBorderBrush}"
+                    Background="{DynamicResource AutoCompleteBoxSuggestionsListBackground}"
+                    CornerRadius="{DynamicResource OverlayCornerRadius}">
               <ListBox Name="PART_SelectingItemsControl"
                        BorderThickness="0"
-                       Background="{TemplateBinding Background}"
-                       Foreground="{TemplateBinding Foreground}"
+                       Background="Transparent"
+                       Foreground="{DynamicResource AutoCompleteBoxSuggestionsListForeground}"
                        ItemTemplate="{TemplateBinding ItemTemplate}"
-                       ScrollViewer.HorizontalScrollBarVisibility="Auto"
-                       ScrollViewer.VerticalScrollBarVisibility="Auto" />
+                       Margin="{DynamicResource AutoCompleteListPadding}" />
             </Border>
           </Popup>
-        </Panel>
+        </Grid>
       </ControlTemplate>
     </Setter>
   </Style>

src/Avalonia.Themes.Fluent/PopupRoot.xaml

@@ -1,17 +1,21 @@
-<Style xmlns="https://github.com/avaloniaui" Selector="PopupRoot">
-  <Setter Property="Background" Value="{DynamicResource ThemeBackgroundBrush}"/>
-  <Setter Property="Template">
-    <ControlTemplate>
-      <Panel>
-        <Border Name="PART_TransparencyFallback" IsHitTestVisible="False" />
-        <VisualLayerManager IsPopup="True">
-          <ContentPresenter Name="PART_ContentPresenter"
-                            Background="{TemplateBinding Background}"
-                            ContentTemplate="{TemplateBinding ContentTemplate}"
-                            Content="{TemplateBinding Content}"
-                            Padding="{TemplateBinding Padding}"/>
-        </VisualLayerManager>
-      </Panel>
-    </ControlTemplate>
-  </Setter>
-</Style>
+<Styles xmlns="https://github.com/avaloniaui"
+        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
+  <Style Selector="PopupRoot">
+    <Setter Property="TransparencyLevelHint" Value="Transparent" />
+    <Setter Property="Background" Value="{x:Null}" />
+    <Setter Property="Template">
+      <ControlTemplate>
+        <Panel>
+          <Border Name="PART_TransparencyFallback" IsHitTestVisible="False" />
+          <VisualLayerManager IsPopup="True">
+            <ContentPresenter Name="PART_ContentPresenter"
+                              Background="{TemplateBinding Background}"
+                              ContentTemplate="{TemplateBinding ContentTemplate}"
+                              Content="{TemplateBinding Content}"
+                              Padding="{TemplateBinding Padding}"/>
+          </VisualLayerManager>
+        </Panel>
+      </ControlTemplate>
+    </Setter>
+  </Style>
+</Styles>

src/Avalonia.X11/X11Window.cs

@@ -1098,6 +1098,10 @@ namespace Avalonia.X11
         public void SetTransparencyLevelHint(WindowTransparencyLevel transparencyLevel) =>
             _transparencyHelper.SetTransparencyRequest(transparencyLevel);
 
+        public void SetWindowManagerAddShadowHint(bool enabled)
+        {
+        }
+
         public WindowTransparencyLevel TransparencyLevel => _transparencyHelper.CurrentLevel;
     }
 }

src/Windows/Avalonia.Win32/PopupImpl.cs

@@ -7,6 +7,8 @@ namespace Avalonia.Win32
 {
     class PopupImpl : WindowImpl, IPopupImpl
     {
+        private bool _dropShadowHint = true;
+
         public override void Show()
         {
             UnmanagedMethods.ShowWindow(Handle.Handle, UnmanagedMethods.ShowWindowCommand.ShowNoActivate);
@@ -36,11 +38,7 @@ namespace Avalonia.Win32
                 IntPtr.Zero,
                 IntPtr.Zero);
 
-            var classes = (int)UnmanagedMethods.GetClassLongPtr(result, (int)UnmanagedMethods.ClassLongIndex.GCL_STYLE);
-
-            classes |= (int)UnmanagedMethods.ClassStyles.CS_DROPSHADOW;
-
-            UnmanagedMethods.SetClassLong(result, UnmanagedMethods.ClassLongIndex.GCL_STYLE, new IntPtr(classes));
+            EnableBoxShadow(result, _dropShadowHint);
 
             return result;
         }
@@ -68,6 +66,32 @@ namespace Avalonia.Win32
             //TODO: We ignore the scaling override for now
         }
 
+        private void EnableBoxShadow (IntPtr hwnd, bool enabled)
+        {
+            var classes = (int)UnmanagedMethods.GetClassLongPtr(hwnd, (int)UnmanagedMethods.ClassLongIndex.GCL_STYLE);
+
+            if (enabled)
+            {
+                classes |= (int)UnmanagedMethods.ClassStyles.CS_DROPSHADOW;
+            }
+            else
+            {
+                classes &= ~(int)UnmanagedMethods.ClassStyles.CS_DROPSHADOW;
+            }
+
+            UnmanagedMethods.SetClassLong(hwnd, UnmanagedMethods.ClassLongIndex.GCL_STYLE, new IntPtr(classes));
+        }
+
+        public void SetWindowManagerAddShadowHint(bool enabled)
+        {
+            _dropShadowHint = enabled;
+
+            if (Handle != null)
+            {
+                EnableBoxShadow(Handle.Handle, enabled);
+            }
+        }
+
         public IPopupPositioner PopupPositioner { get; }
     }
 }