Update Flyout and Popup APIs to make gap between them smaller

samples/ControlCatalog/Pages/ContextFlyoutPage.xaml.cs

@@ -36,8 +36,9 @@ public ContextFlyoutPage()
             customContextRequestedBorder.AddHandler(ContextRequestedEvent, CustomContextRequested, RoutingStrategies.Tunnel);
 
             var cancellableContextBorder = this.Get<Border>("CancellableContextBorder");
-            cancellableContextBorder.ContextFlyout!.Closing += ContextFlyoutPage_Closing;
-            cancellableContextBorder.ContextFlyout!.Opening += ContextFlyoutPage_Opening;
+            var flyout = (Flyout)cancellableContextBorder.ContextFlyout!;
+            flyout.Closing += ContextFlyoutPage_Closing;
+            flyout.Opening += ContextFlyoutPage_Opening;
         }
 
         private ContextPageViewModel? _model;

samples/ControlCatalog/Pages/FlyoutsPage.axaml

@@ -16,8 +16,13 @@
             <MenuItem Header="Item 3" />
         </MenuFlyout>
         <Flyout Placement="Bottom" x:Key="BasicFlyout">
+            <Flyout.FlyoutPresenterTheme>
+                <ControlTheme TargetType="FlyoutPresenter" BasedOn="{StaticResource {x:Type FlyoutPresenter}}">
+                    <Setter Property="CornerRadius" Value="20" />
+                </ControlTheme>
+            </Flyout.FlyoutPresenterTheme>
             <Panel Width="100" Height="100">
-                <TextBlock Text="Flyout Content!" />
+                <TextBlock Text="Flyout Content with a custom presenter theme!" TextWrapping="Wrap" />
             </Panel>
         </Flyout>
     </UserControl.Resources>
@@ -136,6 +141,15 @@
                                 </Flyout>
                             </Button.Flyout>
                         </Button>
+                        <Button Content="Placement=Center">
+                            <Button.Flyout>
+                                <Flyout Placement="Center">
+                                    <Panel Width="100" Height="100">
+                                        <TextBlock Text="Flyout Content!" />
+                                    </Panel>
+                                </Flyout>
+                            </Button.Flyout>
+                        </Button>
                         <Button Content="Placement=TopEdgeAlignedLeft">
                             <Button.Flyout>
                                 <Flyout Placement="TopEdgeAlignedLeft">

src/Avalonia.Base/Input/MouseDevice.cs

@@ -4,6 +4,7 @@
 using Avalonia.Input.Raw;
 using Avalonia.Platform;
 using Avalonia.Utilities;
+#pragma warning disable CS0618
 
 namespace Avalonia.Input
 {

src/Avalonia.Base/Input/PenDevice.cs

@@ -4,6 +4,7 @@
 using System.Reflection;
 using Avalonia.Input.Raw;
 using Avalonia.Platform;
+#pragma warning disable CS0618
 
 namespace Avalonia.Input
 {
@@ -129,7 +130,7 @@ private bool PenUp(Pointer pointer, ulong timestamp,
                 var e = new PointerReleasedEventArgs(source, pointer, (Visual)root, p, timestamp, properties, inputModifiers,
                     _lastMouseDownButton);
 
-                source?.RaiseEvent(e);
+                source.RaiseEvent(e);
                 pointer.Capture(null);
                 _lastMouseDownButton = default;
                 return e.Handled;

src/Avalonia.Base/Input/PointerEventArgs.cs

@@ -42,7 +42,9 @@ internal PointerEventArgs(RoutedEvent routedEvent,
             PointerPointProperties properties,
             KeyModifiers modifiers,
             Lazy<IReadOnlyList<RawPointerPoint>?>? previousPoints)
+#pragma warning disable CS0618
             : this(routedEvent, source, pointer, rootVisual, rootVisualPosition, timestamp, properties, modifiers)
+#pragma warning restore CS0618
         {
             _previousPoints = previousPoints;
         }

src/Avalonia.Base/Input/PointerOverPreProcessor.cs

@@ -6,7 +6,8 @@ namespace Avalonia.Input
     internal class PointerOverPreProcessor : IObserver<RawInputEventArgs>
     {
         private IPointerDevice? _lastActivePointerDevice;
-        private (IPointer pointer, PixelPoint position)? _lastPointer;
+        private (IPointer pointer, PixelPoint position)? _currentPointer;
+        private PixelPoint? _lastKnownPosition;
 
         private readonly IInputRoot _inputRoot;
 
@@ -15,7 +16,7 @@ public PointerOverPreProcessor(IInputRoot inputRoot)
             _inputRoot = inputRoot ?? throw new ArgumentNullException(nameof(inputRoot));
         }
 
-        public PixelPoint? LastPosition => _lastPointer?.position;
+        public PixelPoint? LastPosition => _lastKnownPosition;
 
         public void OnCompleted()
         {
@@ -41,14 +42,14 @@ public void OnNext(RawInputEventArgs value)
                 }
 
                 if (args.Type is RawPointerEventType.LeaveWindow or RawPointerEventType.NonClientLeftButtonDown
-                    && _lastPointer is (var lastPointer, var lastPosition))
+                    && _currentPointer is var (lastPointer, lastPosition))
                 {
-                    _lastPointer = null;
+                    _currentPointer = null;
                     ClearPointerOver(lastPointer, args.Root, 0, PointToClient(args.Root, lastPosition),
                         new PointerPointProperties(args.InputModifiers, args.Type.ToUpdateKind()),
                         args.InputModifiers.ToKeyModifiers());
                 }
-                else if (pointerDevice.TryGetPointer(args) is IPointer pointer
+                else if (pointerDevice.TryGetPointer(args) is { } pointer
                     && pointer.Type != PointerType.Touch)
                 {
                     var element = pointer.Captured ?? args.InputHitTestResult;
@@ -62,7 +63,7 @@ public void OnNext(RawInputEventArgs value)
 
         public void SceneInvalidated(Rect dirtyRect)
         {
-            if (_lastPointer is (var pointer, var position))
+            if (_currentPointer is (var pointer, var position))
             {
                 var clientPoint = PointToClient(_inputRoot, position);
 
@@ -80,12 +81,12 @@ public void SceneInvalidated(Rect dirtyRect)
 
         private void ClearPointerOver()
         {
-            if (_lastPointer is (var pointer, var position))
+            if (_currentPointer is (var pointer, var position))
             {
                 var clientPoint = PointToClient(_inputRoot, position);
                 ClearPointerOver(pointer, _inputRoot, 0, clientPoint, PointerPointProperties.None, KeyModifiers.None);
             }
-            _lastPointer = null;
+            _currentPointer = null;
             _lastActivePointerDevice = null;
         }
 
@@ -100,9 +101,11 @@ private void ClearPointerOver(IPointer pointer, IInputRoot root,
 
             // Do not pass rootVisual, when we have unknown position,
             // so GetPosition won't return invalid values.
+#pragma warning disable CS0618
             var e = new PointerEventArgs(InputElement.PointerExitedEvent, element, pointer,
                 position.HasValue ? root as Visual : null, position.HasValue ? position.Value : default,
                 timestamp, properties, inputModifiers);
+#pragma warning restore CS0618
 
             if (element is Visual v && !v.IsAttachedToVisualTree)
             {
@@ -122,18 +125,18 @@ private void ClearPointerOver(IPointer pointer, IInputRoot root,
 
             root.PointerOverElement = null;
             _lastActivePointerDevice = null;
-            _lastPointer = null;
+            _currentPointer = null;
         }
 
         private void ClearChildrenPointerOver(PointerEventArgs e, IInputElement element, bool clearRoot)
         {
             if (element is Visual v)
             {
-                foreach (IInputElement el in v.VisualChildren)
+                foreach (var el in v.VisualChildren)
                 {
-                    if (el.IsPointerOver)
+                    if (el is IInputElement { IsPointerOver: true } child)
                     {
-                        ClearChildrenPointerOver(e, el, true);
+                        ClearChildrenPointerOver(e, child, true);
                         break;
                     }
                 }
@@ -151,6 +154,8 @@ private void SetPointerOver(IPointer pointer, IInputRoot root, IInputElement? el
             ulong timestamp, Point position, PointerPointProperties properties, KeyModifiers inputModifiers)
         {
             var pointerOverElement = root.PointerOverElement;
+            var screenPosition = ((Visual)root).PointToScreen(position);
+            _lastKnownPosition = screenPosition;
 
             if (element != pointerOverElement)
             {
@@ -164,7 +169,7 @@ private void SetPointerOver(IPointer pointer, IInputRoot root, IInputElement? el
                 }
             }
 
-            _lastPointer = (pointer, ((Visual)root).PointToScreen(position));
+            _currentPointer = (pointer, screenPosition);
         }
 
         private void SetPointerOverToElement(IPointer pointer, IInputRoot root, IInputElement element,
@@ -186,8 +191,10 @@ private void SetPointerOverToElement(IPointer pointer, IInputRoot root, IInputEl
 
             el = root.PointerOverElement;
 
+#pragma warning disable CS0618
             var e = new PointerEventArgs(InputElement.PointerExitedEvent, el, pointer, (Visual)root, position,
                 timestamp, properties, inputModifiers);
+#pragma warning restore CS0618
             if (el is Visual v && branch != null && !v.IsAttachedToVisualTree)
             {
                 ClearChildrenPointerOver(e, branch, false);

src/Avalonia.Base/Input/TouchDevice.cs

@@ -4,6 +4,7 @@
 using System.Reflection;
 using Avalonia.Input.Raw;
 using Avalonia.Platform;
+#pragma warning disable CS0618
 
 namespace Avalonia.Input
 {

src/Avalonia.Controls/Flyouts/Flyout.cs

@@ -1,9 +1,11 @@
-using Avalonia.Controls.Primitives;
+using System.ComponentModel;
+using Avalonia.Controls.Primitives;
 using Avalonia.Metadata;
+using Avalonia.Styling;
 
 namespace Avalonia.Controls
 {
-    public class Flyout : FlyoutBase
+    public class Flyout : PopupFlyoutBase
     {
         /// <summary>
         /// Defines the <see cref="Content"/> property
@@ -18,6 +20,21 @@ public class Flyout : FlyoutBase
 
         private Classes? _classes;
 
+        /// <summary>
+        /// Defines the <see cref="FlyoutPresenterTheme"/> property.
+        /// </summary>
+        public static readonly StyledProperty<ControlTheme?> FlyoutPresenterThemeProperty =
+            AvaloniaProperty.Register<Flyout, ControlTheme?>(nameof(FlyoutPresenterTheme));
+
+        /// <summary>
+        /// Gets or sets the <see cref="ControlTheme"/> that is applied to the container element generated for the flyout presenter.
+        /// </summary>
+        public ControlTheme? FlyoutPresenterTheme
+        {
+            get => GetValue(FlyoutPresenterThemeProperty); 
+            set => SetValue(FlyoutPresenterThemeProperty, value);
+        }
+
         /// <summary>
         /// Gets or sets the content to display in this flyout
         /// </summary>
@@ -36,13 +53,22 @@ protected override Control CreatePresenter()
             };
         }
 
-        protected override void OnOpened()
+        protected override void OnOpening(CancelEventArgs args)
         {
-            if (_classes != null)
+            if (Popup.Child is { } presenter)
             {
-                SetPresenterClasses(Popup.Child, FlyoutPresenterClasses);
+                if (_classes != null)
+                {
+                    SetPresenterClasses(presenter, FlyoutPresenterClasses);
+                }
+
+                if (FlyoutPresenterTheme is { } theme)
+                {
+                    presenter.SetValue(Control.ThemeProperty, theme);
+                }
             }
-            base.OnOpened();
+
+            base.OnOpening(args);
         }
     }
 }