Internal API for rounded border clip for usage with Border.

samples/ControlCatalog/Pages/BorderPage.xaml

@@ -29,6 +29,13 @@
               Padding="16">
         <TextBlock>Rounded Corners</TextBlock>
       </Border>
+      <Border BorderBrush="{DynamicResource ThemeAccentBrush2}"
+              BorderThickness="4"
+              CornerRadius="8" ClipToBounds="True">
+        <Border Background="Red" Padding="16">
+          <TextBlock>Clipped Rounded Corners</TextBlock>
+        </Border>
+      </Border>
     </StackPanel>    
   </StackPanel>
 </UserControl>

src/Avalonia.Controls/Border.cs

@@ -1,13 +1,14 @@
 using Avalonia.Controls.Utils;
 using Avalonia.Layout;
 using Avalonia.Media;
+using Avalonia.VisualTree;
 
 namespace Avalonia.Controls
 {
     /// <summary>
     /// A control which decorates a child with a border and background.
     /// </summary>
-    public partial class Border : Decorator
+    public partial class Border : Decorator, IVisualWithRoundRectClip
     {
         /// <summary>
         /// Defines the <see cref="Background"/> property.
@@ -129,5 +130,7 @@ namespace Avalonia.Controls
         {
             return LayoutHelper.ArrangeChild(Child, finalSize, Padding, BorderThickness);
         }
+
+        public CornerRadius ClipToBoundsRadius => CornerRadius;
     }
 }

src/Avalonia.Visuals/Rendering/ImmediateRenderer.cs

@@ -289,7 +289,11 @@ namespace Avalonia.Rendering
 
                 using (context.PushPostTransform(m))
                 using (context.PushOpacity(opacity))
-                using (clipToBounds ? context.PushClip(bounds) : default(DrawingContext.PushedState))
+                using (clipToBounds 
+                    ? visual is IVisualWithRoundRectClip roundClipVisual 
+                        ? context.PushClip(new RoundedRect(bounds, roundClipVisual.ClipToBoundsRadius))
+                        : context.PushClip(bounds) 
+                    : default(DrawingContext.PushedState))
                 using (visual.Clip != null ? context.PushGeometryClip(visual.Clip) : default(DrawingContext.PushedState))
                 using (visual.OpacityMask != null ? context.PushOpacityMask(visual.OpacityMask, bounds) : default(DrawingContext.PushedState))
                 using (context.PushTransformContainer())

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

@@ -16,6 +16,16 @@ namespace Avalonia.Rendering.SceneGraph
         {
             Clip = clip;
         }
+        
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ClipNode"/> class that represents a
+        /// clip push.
+        /// </summary>
+        /// <param name="clip">The clip to push.</param>
+        public ClipNode(RoundedRect clip)
+        {
+            Clip = clip;
+        }
 
         /// <summary>
         /// Initializes a new instance of the <see cref="ClipNode"/> class that represents a
@@ -31,7 +41,7 @@ namespace Avalonia.Rendering.SceneGraph
         /// <summary>
         /// Gets the clip to be pushed or null if the operation represents a pop.
         /// </summary>
-        public Rect? Clip { get; }
+        public RoundedRect? Clip { get; }
 
         /// <inheritdoc/>
         public bool HitTest(Point p) => false;
@@ -45,7 +55,7 @@ namespace Avalonia.Rendering.SceneGraph
         /// The properties of the other draw operation are passed in as arguments to prevent
         /// allocation of a not-yet-constructed draw operation object.
         /// </remarks>
-        public bool Equals(Rect? clip) => Clip == clip;
+        public bool Equals(RoundedRect? clip) => Clip == clip;
 
         /// <inheritdoc/>
         public void Render(IDrawingContextImpl context)

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

@@ -207,7 +207,7 @@ namespace Avalonia.Rendering.SceneGraph
         {
             throw new NotSupportedException("Creating layers on a deferred drawing context not supported");
         }
-
+        
         /// <inheritdoc/>
         public void PopClip()
         {
@@ -282,6 +282,21 @@ namespace Avalonia.Rendering.SceneGraph
                 ++_drawOperationindex;
             }
         }
+        
+        /// <inheritdoc />
+        public void PushClip(RoundedRect clip)
+        {
+            var next = NextDrawAs<ClipNode>();
+
+            if (next == null || !next.Item.Equals(clip))
+            {
+                Add(new ClipNode(clip));
+            }
+            else
+            {
+                ++_drawOperationindex;
+            }
+        }
 
         /// <inheritdoc/>
         public void PushGeometryClip(IGeometryImpl clip)

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

@@ -29,7 +29,7 @@ namespace Avalonia.Rendering.SceneGraph
         /// <summary>
         /// Gets the corner radius of visual. Contents are clipped to this radius.
         /// </summary>
-        CornerRadius CornerRadius { get; }
+        CornerRadius ClipToBoundsRadius { get; }
 
         /// <summary>
         /// Gets the bounds of the node's geometry in global coordinates.

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

@@ -163,6 +163,10 @@ namespace Avalonia.Rendering.SceneGraph
             var visual = node.Visual;
             var opacity = visual.Opacity;
             var clipToBounds = visual.ClipToBounds;
+            var clipToBoundsRadius = visual is IVisualWithRoundRectClip roundRectClip ?
+                roundRectClip.ClipToBoundsRadius :
+                default;
+            
             var bounds = new Rect(visual.Bounds.Size);
             var contextImpl = (DeferredDrawingContextImpl)context.PlatformImpl;
 
@@ -201,6 +205,7 @@ namespace Avalonia.Rendering.SceneGraph
                     node.ClipBounds = clipBounds;
                     node.ClipToBounds = clipToBounds;
                     node.LayoutBounds = globalBounds;
+                    node.ClipToBoundsRadius = clipToBoundsRadius;
                     node.GeometryClip = visual.Clip?.PlatformImpl;
                     node.Opacity = opacity;
 

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

@@ -47,7 +47,7 @@ namespace Avalonia.Rendering.SceneGraph
         public IVisualNode Parent { get; }
 
         /// <inheritdoc/>
-        public CornerRadius CornerRadius { get; }
+        public CornerRadius ClipToBoundsRadius { get; set; }
 
         /// <inheritdoc/>
         public Matrix Transform { get; set; }
@@ -265,6 +265,7 @@ namespace Avalonia.Rendering.SceneGraph
             {
                 Transform = Transform,
                 ClipBounds = ClipBounds,
+                ClipToBoundsRadius =  ClipToBoundsRadius,
                 ClipToBounds = ClipToBounds,
                 LayoutBounds = LayoutBounds,
                 GeometryClip = GeometryClip,
@@ -304,7 +305,10 @@ namespace Avalonia.Rendering.SceneGraph
             if (ClipToBounds)
             {
                 context.Transform = Matrix.Identity;
-                context.PushClip(ClipBounds);
+                if (ClipToBoundsRadius.IsEmpty)
+                    context.PushClip(ClipBounds);
+                else
+                    context.PushClip(new RoundedRect(ClipBounds, ClipToBoundsRadius));
             }
 
             context.Transform = Transform;

src/Avalonia.Visuals/RoundedRect.cs

@@ -27,6 +27,10 @@ namespace Avalonia
             }
         }
 
+        public static bool operator ==(RoundedRect left, RoundedRect right) => left.Equals(right);
+
+        public static bool operator !=(RoundedRect left, RoundedRect right) => !left.Equals(right);
+
         public Rect Rect { get; }
         public Vector RadiiTopLeft { get; }
         public Vector RadiiTopRight { get; }
@@ -74,6 +78,13 @@ namespace Avalonia
             
         }
 
+        public RoundedRect(in Rect bounds, in CornerRadius radius) : this(bounds,
+            radius.TopLeft, radius.TopRight,
+            radius.BottomRight, radius.BottomLeft)
+        {
+
+        }
+
         public static implicit operator RoundedRect(Rect r) => new RoundedRect(r);
 
         public bool IsRounded => RadiiTopLeft != default || RadiiTopRight != default || RadiiBottomRight != default ||

src/Avalonia.Visuals/VisualTree/IVisualWithRoundRectClip.cs

@@ -0,0 +1,15 @@
+using System;
+
+namespace Avalonia.VisualTree
+{
+    [Obsolete("Internal API, will be removed in future versions, you've been warned")]
+    public interface IVisualWithRoundRectClip
+    {
+        /// <summary>
+        /// Gets a value indicating the corner radius of control's clip bounds
+        /// </summary>
+        [Obsolete("Internal API, will be removed in future versions, you've been warned")]
+        CornerRadius ClipToBoundsRadius { get; }
+
+    }
+}

src/Windows/Avalonia.Direct2D1/Media/DrawingContextImpl.cs

@@ -359,6 +359,12 @@ namespace Avalonia.Direct2D1.Media
             _deviceContext.PushAxisAlignedClip(clip.ToSharpDX(), AntialiasMode.PerPrimitive);
         }
 
+        public void PushClip(RoundedRect clip)
+        {
+            //TODO: radius
+            _deviceContext.PushAxisAlignedClip(clip.Rect.ToDirect2D(), AntialiasMode.PerPrimitive);
+        }
+
         public void PopClip()
         {
             _deviceContext.PopAxisAlignedClip();