perf: reduce SKPaint and SKPath allocations

src/SamplesApp/UITests.Shared/UITests.Shared.projitems

@@ -5350,6 +5350,10 @@
       <SubType>Designer</SubType>
       <Generator>MSBuild:Compile</Generator>
     </Page>
+    <Page Include="$(MSBuildThisFileDirectory)Windows_UI_Xaml_Shapes\Path_Clipping.xaml">
+      <SubType>Designer</SubType>
+      <Generator>MSBuild:Compile</Generator>
+    </Page>
     <Page Include="$(MSBuildThisFileDirectory)Windows_UI_Xaml_Shapes\Path_Geometries.xaml">
       <SubType>Designer</SubType>
       <Generator>MSBuild:Compile</Generator>
@@ -8797,6 +8801,9 @@
     <Compile Include="$(MSBuildThisFileDirectory)Windows_UI_Xaml_Shapes\Path_Custom.xaml.cs">
       <DependentUpon>Path_Custom.xaml</DependentUpon>
     </Compile>
+    <Compile Include="$(MSBuildThisFileDirectory)Windows_UI_Xaml_Shapes\Path_Clipping.xaml.cs">
+      <DependentUpon>Path_Clipping.xaml</DependentUpon>
+    </Compile>
     <Compile Include="$(MSBuildThisFileDirectory)Windows_UI_Xaml_Shapes\Path_Geometries.xaml.cs">
       <DependentUpon>Path_Geometries.xaml</DependentUpon>
     </Compile>
@@ -9841,4 +9848,4 @@
     </Compile>
   </ItemGroup>
   <Import Project="ItemExclusions.props" />
-</Project>
+</Project>

src/SamplesApp/UITests.Shared/Windows_UI_Xaml_Shapes/Path_Clipping.xaml

@@ -0,0 +1,20 @@
+<Page
+    x:Class="UITests.Windows_UI_Xaml_Shapes.Path_Clipping"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+    xmlns:local="using:UITests.Windows_UI_Xaml_Shapes"
+    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+    Background="{ThemeResource ApplicationPageBackgroundThemeBrush}"
+    mc:Ignorable="d">
+
+    <StackPanel>
+		<TextBlock Text="The two icons below should not be the same (the first one should be clipped)." />
+		<Border Height="16" HorizontalAlignment="Stretch" />
+		<ScrollViewer Height="30" x:Name="sv">
+			<Path Fill="Red" Data="m 0,0 c -0.639,0 -1.276,0.243 -1.765,0.729 -0.977,0.974 -0.98,2.557 -0.006,3.535 L 16.925,23.032 -1.768,41.725 c -0.976,0.976 -0.976,2.559 0,3.535 0.977,0.976 2.559,0.976 3.536,0 L 22.225,24.803 c 0.975,-0.975 0.976,-2.555 0.004,-3.532 L 1.771,0.736 C 1.283,0.245 0.642,0 0,0" />
+		</ScrollViewer>
+		<TextBlock Text="------------" />
+		<Path Fill="Red" Data="m 0,0 c -0.639,0 -1.276,0.243 -1.765,0.729 -0.977,0.974 -0.98,2.557 -0.006,3.535 L 16.925,23.032 -1.768,41.725 c -0.976,0.976 -0.976,2.559 0,3.535 0.977,0.976 2.559,0.976 3.536,0 L 22.225,24.803 c 0.975,-0.975 0.976,-2.555 0.004,-3.532 L 1.771,0.736 C 1.283,0.245 0.642,0 0,0" />
+	</StackPanel>
+</Page>

src/SamplesApp/UITests.Shared/Windows_UI_Xaml_Shapes/Path_Clipping.xaml.cs

@@ -0,0 +1,15 @@
+using Uno.UI.Samples.Controls;
+using Microsoft.UI.Xaml.Controls;
+
+namespace UITests.Windows_UI_Xaml_Shapes
+{
+	[Sample("Shapes", IsManualTest = true)]
+	public sealed partial class Path_Clipping : Page
+	{
+		public Path_Clipping()
+		{
+			this.InitializeComponent();
+			Loaded += (_, _) => sv.ScrollToVerticalOffset(9999);
+		}
+	}
+}

src/Uno.UI.Composition/Composition/CompositionMaskBrush.skia.cs

@@ -14,7 +14,6 @@ public partial class CompositionMaskBrush : CompositionBrush, IOnlineBrush
 	{
 		private SKPaint? _sourcePaint;
 		private SKPaint? _maskPaint;
-		private SKPaint? _resultPaint;
 
 		bool IOnlineBrush.IsOnline
 		{
@@ -36,10 +35,13 @@ internal override void UpdatePaint(SKPaint paint, SKRect bounds)
 
 		void IOnlineBrush.Paint(in Visual.PaintingSession session, SKRect bounds)
 		{
-			_resultPaint ??= new SKPaint() { IsAntialias = true };
+			using (SkiaHelper.GetTempSKPaint(out var resultPaint))
+			{
+				resultPaint.IsAntialias = true;
 
-			UpdatePaint(_resultPaint, bounds);
-			session.Canvas?.DrawRect(bounds, _resultPaint);
+				UpdatePaint(resultPaint, bounds);
+				session.Canvas?.DrawRect(bounds, resultPaint);
+			}
 		}
 
 		private protected override void DisposeInternal()
@@ -48,7 +50,6 @@ private protected override void DisposeInternal()
 
 			_sourcePaint?.Dispose();
 			_maskPaint?.Dispose();
-			_resultPaint?.Dispose();
 		}
 	}
 }

src/Uno.UI.Composition/Composition/CompositionSpriteShape.skia.cs

@@ -3,14 +3,13 @@
 using Windows.Foundation;
 using SkiaSharp;
 using Uno;
+using Uno.Disposables;
 using Uno.Extensions;
 
 namespace Microsoft.UI.Composition
 {
 	public partial class CompositionSpriteShape : CompositionShape
 	{
-		private SKPaint? _strokePaint;
-		private SKPaint? _fillPaint;
 		private SKPath? _geometryWithTransformations;
 
 		internal override void Paint(in Visual.PaintingSession session)
@@ -19,7 +18,7 @@ internal override void Paint(in Visual.PaintingSession session)
 			{
 				if (FillBrush is { } fill)
 				{
-					var fillPaint = TryCreateAndClearFillPaint(session.Filters.OpacityColorFilter);
+					using var fillPaintDisposable = GetTempFillPaint(session.Filters.OpacityColorFilter, out var fillPaint);
 
 					if (Compositor.TryGetEffectiveBackgroundColor(this, out var colorFromTransition))
 					{
@@ -52,8 +51,8 @@ internal override void Paint(in Visual.PaintingSession session)
 
 				if (StrokeBrush is { } stroke && StrokeThickness > 0)
 				{
-					var fillPaint = TryCreateAndClearFillPaint(session.Filters.OpacityColorFilter);
-					var strokePaint = TryCreateAndClearStrokePaint(session.Filters.OpacityColorFilter);
+					using var fillPaintDisposable = GetTempFillPaint(session.Filters.OpacityColorFilter, out var fillPaint);
+					using var strokePaintDisposable = GetTempStrokePaint(session.Filters.OpacityColorFilter, out var strokePaint);
 
 					// Set stroke thickness
 					strokePaint.StrokeWidth = StrokeThickness;
@@ -78,59 +77,45 @@ internal override void Paint(in Visual.PaintingSession session)
 					// On Windows, the stroke is simply 1px, it doesn't scale with the height.
 					// So, to get a correct stroke geometry, we must apply the transformations first.
 
-					// Get the stroke geometry, after scaling has been applied.
-					var strokeGeometry = strokePaint.GetFillPath(geometryWithTransformations);
+					using (SkiaHelper.GetTempSKPath(out var strokeFillPath))
+					{
+						// Get the stroke geometry, after scaling has been applied.
+						strokePaint.GetFillPath(geometryWithTransformations, strokeFillPath);
 
-					stroke.UpdatePaint(fillPaint, strokeGeometry.Bounds);
+						stroke.UpdatePaint(fillPaint, strokeFillPath.Bounds);
 
-					session.Canvas.DrawPath(strokeGeometry, fillPaint);
+						session.Canvas.DrawPath(strokeFillPath, fillPaint);
+					}
 				}
 			}
 		}
 
-		private SKPaint TryCreateAndClearStrokePaint(SKColorFilter? colorFilter)
-			=> TryCreateAndClearPaint(ref _strokePaint, true, colorFilter, CompositionConfiguration.UseBrushAntialiasing);
+		private DisposableStruct<SKPaint> GetTempStrokePaint(SKColorFilter? colorFilter, out SKPaint paint)
+			=> GetTempPaint(out paint, true, colorFilter, CompositionConfiguration.UseBrushAntialiasing);
 
-		private SKPaint TryCreateAndClearFillPaint(SKColorFilter? colorFilter)
-			=> TryCreateAndClearPaint(ref _fillPaint, false, colorFilter, CompositionConfiguration.UseBrushAntialiasing);
+		private DisposableStruct<SKPaint> GetTempFillPaint(SKColorFilter? colorFilter, out SKPaint paint)
+			=> GetTempPaint(out paint, false, colorFilter, CompositionConfiguration.UseBrushAntialiasing);
 
-		private static SKPaint TryCreateAndClearPaint(ref SKPaint? paint, bool isStroke, SKColorFilter? colorFilter, bool isHighQuality = false)
+		private static DisposableStruct<SKPaint> GetTempPaint(out SKPaint paint, bool isStroke, SKColorFilter? colorFilter, bool isHighQuality = false)
 		{
-			if (paint == null)
-			{
-				// Initialization
-				paint = new SKPaint();
-				paint.IsStroke = isStroke;
-				paint.IsAntialias = true;
-				paint.IsAutohinted = true;
+			var disposable = SkiaHelper.GetTempSKPaint(out paint);
+			paint.IsAntialias = true;
+			paint.ColorFilter = colorFilter;
 
-				if (isHighQuality)
-				{
-					paint.FilterQuality = SKFilterQuality.High;
-				}
-			}
-			else
-			{
-				// Cleanup
-				// - Brushes can change, we cant leave color and shader garbage
-				//	 from last rendering around for the next pass.
-				paint.Color = SKColors.White;   // Transparent color wouldn't draw anything
-				if (paint.Shader is { } shader)
-				{
-					shader.Dispose();
-					paint.Shader = null;
-				}
+			paint.IsStroke = isStroke;
 
-				if (paint.PathEffect is { } pathEffect)
-				{
-					pathEffect.Dispose();
-					paint.PathEffect = null;
-				}
-			}
+			// uno-specific defaults
+			paint.Color = SKColors.White;   // Transparent color wouldn't draw anything
+			paint.IsAutohinted = true;
+			// paint.IsAntialias = true; // IMPORTANT: don't set this to true by default. It breaks canvas clipping on Linux for some reason.
 
 			paint.ColorFilter = colorFilter;
+			if (isHighQuality)
+			{
+				paint.FilterQuality = SKFilterQuality.High;
+			}
 
-			return paint;
+			return disposable;
 		}
 
 		private protected override void OnPropertyChangedCore(string? propertyName, bool isSubPropertyChange)
@@ -175,14 +160,20 @@ internal override bool HitTest(Point point)
 					return true;
 				}
 
-				if (StrokeBrush is { } stroke && StrokeThickness > 0)
+				if (StrokeBrush is { } && StrokeThickness > 0)
 				{
-					var strokePaint = TryCreateAndClearStrokePaint(null);
-					strokePaint.StrokeWidth = StrokeThickness;
-					var strokeGeometry = strokePaint.GetFillPath(geometryWithTransformations);
-					if (strokeGeometry.Contains((float)point.X, (float)point.Y))
+					using (GetTempStrokePaint(null, out var strokePaint))
 					{
-						return true;
+						strokePaint.StrokeWidth = StrokeThickness;
+
+						using (SkiaHelper.GetTempSKPath(out var hitTestStrokeFillPath))
+						{
+							strokePaint.GetFillPath(geometryWithTransformations, hitTestStrokeFillPath);
+							if (hitTestStrokeFillPath.Contains((float)point.X, (float)point.Y))
+							{
+								return true;
+							}
+						}
 					}
 				}
 			}

src/Uno.UI.Composition/Composition/ShapeVisual.skia.cs

@@ -1,5 +1,6 @@
 #nullable enable
 
+using System;
 using System.Numerics;
 using Windows.Foundation;
 using SkiaSharp;
@@ -12,9 +13,12 @@ public partial class ShapeVisual
 	private protected override void ApplyPrePaintingClipping(in SKCanvas canvas)
 	{
 		base.ApplyPrePaintingClipping(in canvas);
-		if (GetViewBoxPathInElementCoordinateSpace() is { } path)
+		using (SkiaHelper.GetTempSKPath(out var prePaintingClipPath))
 		{
-			canvas.ClipPath(path, antialias: true);
+			if (GetViewBoxPathInElementCoordinateSpace(prePaintingClipPath))
+			{
+				canvas.ClipPath(prePaintingClipPath, antialias: true);
+			}
 		}
 	}
 
@@ -32,28 +36,28 @@ internal override void Paint(in PaintingSession session)
 		base.Paint(in session);
 	}
 
-	internal SKPath? GetViewBoxPathInElementCoordinateSpace()
+	/// <returns>true if a ViewBox exists</returns>
+	internal bool GetViewBoxPathInElementCoordinateSpace(SKPath dst)
 	{
 		if (ViewBox is not { } viewBox)
 		{
-			return null;
+			return false;
 		}
 
-		var shape = new SKPath();
+		dst.Rewind();
 		var clipRect = new SKRect(viewBox.Offset.X, viewBox.Offset.Y, viewBox.Offset.X + viewBox.Size.X, viewBox.Offset.Y + viewBox.Size.Y);
-		shape.AddRect(clipRect);
+		dst.AddRect(clipRect);
 		if (viewBox.IsAncestorClip)
 		{
 			Matrix4x4.Invert(TotalMatrix, out var totalMatrixInverted);
 			var childToParentTransform = Parent!.TotalMatrix * totalMatrixInverted;
 			if (!childToParentTransform.IsIdentity)
 			{
-
-				shape.Transform(childToParentTransform.ToSKMatrix());
+				dst.Transform(childToParentTransform.ToSKMatrix());
 			}
 		}
 
-		return shape;
+		return true;
 	}
 
 	/// <remarks>This does NOT take the clipping into account.</remarks>

src/Uno.UI.Composition/Composition/SkiaHelper.skia.cs

@@ -0,0 +1,33 @@
+#nullable enable
+
+using SkiaSharp;
+using Microsoft.CodeAnalysis.PooledObjects;
+using Uno.Disposables;
+using SKPaint = SkiaSharp.SKPaint;
+
+namespace Microsoft.UI.Composition
+{
+	internal static class SkiaHelper
+	{
+		private static readonly ObjectPool<SKPaint> _paintPool = new(() => new SKPaint(), 8);
+		private static readonly ObjectPool<SKPath> _pathPool = new(() => new SKPath(), 8);
+
+		public static DisposableStruct<SKPath> GetTempSKPath(out SKPath path)
+		{
+			path = _pathPool.Allocate();
+			// Note the difference between Rewind and Reset
+			// https://api.skia.org/classSkPath.html#a8dc858ee4c95a59b3dd4bdd3f7b85fdc : "Use rewind() instead of reset() if SkPath storage will be reused and performance is critical."
+			path.Rewind();
+			return new DisposableStruct<SKPath>(p => _pathPool.Free(p), path);
+		}
+
+		public static DisposableStruct<SKPaint> GetTempSKPaint(out SKPaint paint)
+		{
+			paint = _paintPool.Allocate();
+			// https://api.skia.org/classSkPaint.html#a6c7118c97a0e8819d75aa757afbc4c49
+			// "This is equivalent to replacing SkPaint with the result of SkPaint()."
+			paint.Reset();
+			return new DisposableStruct<SKPaint>(p => _paintPool.Free(p), paint);
+		}
+	}
+}

src/Uno.UI/UI/Xaml/Controls/TextBlock/TextBlock.skia.cs

@@ -188,11 +188,13 @@ partial void SetupInlines()
 			{
 				var canvas = t.canvas;
 				var rect = t.rect;
-				canvas.DrawRect(new SKRect((float)rect.Left, (float)rect.Top, (float)rect.Right, (float)rect.Bottom), new SKPaint
+
+				using (SkiaHelper.GetTempSKPaint(out var paint))
 				{
-					Color = SelectionHighlightColor.Color.ToSKColor(),
-					Style = SKPaintStyle.Fill
-				});
+					paint.Color = SelectionHighlightColor.Color.ToSKColor();
+					paint.Style = SKPaintStyle.Fill;
+					canvas.DrawRect(new SKRect((float)rect.Left, (float)rect.Top, (float)rect.Right, (float)rect.Bottom), paint);
+				}
 			};
 
 			_inlines.RenderSelection = IsTextSelectionEnabled;

src/Uno.UI/UI/Xaml/Controls/TextBox/TextBox.skia.cs

@@ -239,11 +239,13 @@ private void UpdateTextBoxView()
 							var caretRect = args.rect;
 							var compositor = _visual.Compositor;
 							var brush = DefaultBrushes.TextForegroundBrush.GetOrCreateCompositionBrush(compositor);
-							var caretPaint = new SKPaint(); // we create a new caret everytime to dodge the complications that occur when trying to "reset" an SKPaint.
-							brush.UpdatePaint(caretPaint, caretRect.ToSKRect());
-							args.canvas.DrawRect(
-								new SKRect((float)caretRect.Left, (float)caretRect.Top, (float)caretRect.Right,
-									(float)caretRect.Bottom), caretPaint);
+							using (SkiaHelper.GetTempSKPaint(out var caretPaint))
+							{
+								brush.UpdatePaint(caretPaint, caretRect.ToSKRect());
+								args.canvas.DrawRect(
+									new SKRect((float)caretRect.Left, (float)caretRect.Top, (float)caretRect.Right,
+										(float)caretRect.Bottom), caretPaint);
+							}
 						}
 
 						if ((CaretMode == CaretDisplayMode.CaretWithThumbsOnlyEndShowing && args.endCaret) ||

src/Uno.UI/UI/Xaml/Documents/Inline.skia.cs

@@ -10,22 +10,6 @@ namespace Microsoft.UI.Xaml.Documents
 	partial class Inline
 	{
 		private FontDetails? _fontInfo;
-		private SKPaint? _paint;
-
-		internal SKPaint Paint
-		{
-			get
-			{
-				var paint = _paint ??= new SKPaint()
-				{
-					TextEncoding = SKTextEncoding.Utf16,
-					IsStroke = false,
-					IsAntialias = true,
-				};
-
-				return paint;
-			}
-		}
 
 		internal FontDetails FontInfo
 		{