功能完善

NeuWPF/NeoUI/Controls/Decorations/ClippingBorder.cs

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+namespace NeumUI.Controls.Decorations;
+
+/// <summary>
+/// 可裁剪 Boder
+/// </summary>
+public class ClippingBorder : System.Windows.Controls.Border
+{
+    /// <inheritdoc/>
+    protected override void OnRender(DrawingContext dc)
+    {
+        if(Child is { })
+        {
+            var topLeft = CornerRadius.TopLeft - Math.Max(BorderThickness.Top, BorderThickness.Left) / 2;
+            var bottomLeft = CornerRadius.BottomLeft - Math.Max(BorderThickness.Bottom, BorderThickness.Left) / 2;
+            var topRight = CornerRadius.TopRight - Math.Max(BorderThickness.Top, BorderThickness.Right) / 2;
+            var bottomRight = CornerRadius.BottomRight - Math.Max(BorderThickness.Bottom, BorderThickness.Right) / 2;
+            if(topLeft < 0)
+                topLeft = 0;
+            if(bottomLeft < 0)
+                bottomLeft = 0;
+            if(topRight < 0)
+                topRight = 0;
+            if(bottomRight < 0)
+                bottomRight = 0;
+            var mask = new System.Windows.Controls.Border()
+            {
+                CornerRadius = new CornerRadius(topLeft, topRight, bottomRight, bottomLeft),
+                Height = ActualHeight - BorderThickness.Top - BorderThickness.Bottom,
+                Width = ActualWidth - BorderThickness.Left - BorderThickness.Right,
+                Background = Brushes.Black,
+                SnapsToDevicePixels = true,
+            };
+
+            Child.OpacityMask = new VisualBrush(mask);
+        }
+
+        base.OnRender(dc);
+    }
+}