From c7162dbc4764d413d87e785ad55c445245626729 Mon Sep 17 00:00:00 2001
From: Matthew Leibowitz <mattleibow@live.com>
Date: Mon, 27 Apr 2020 21:50:40 +0200
Subject: [PATCH] First go at a zero-allocation

---
 .../SkiaSharp.Views.UWP/SKSwapChainPanel.cs    | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/source/SkiaSharp.Views/SkiaSharp.Views.UWP/SKSwapChainPanel.cs b/source/SkiaSharp.Views/SkiaSharp.Views.UWP/SKSwapChainPanel.cs
index a04e2073d3..c76e6a3c54 100644
--- a/source/SkiaSharp.Views/SkiaSharp.Views.UWP/SKSwapChainPanel.cs
+++ b/source/SkiaSharp.Views/SkiaSharp.Views.UWP/SKSwapChainPanel.cs
@@ -18,6 +18,9 @@ public class SKSwapChainPanel : AngleSwapChainPanel
 
 		private SKSizeI lastSize;
 
+		private SKPaintGLSurfaceEventArgs lastPaintEventArgs;
+		private bool reusePaintEventArgsInstance = true;
+
 		public SKSwapChainPanel()
 		{
 		}
@@ -80,14 +83,18 @@ protected override void OnRenderFrame(Rect rect)
 			{
 				surface = SKSurface.Create(context, renderTarget, surfaceOrigin, colorType);
 				canvas = surface.Canvas;
-			}
 
-			using (new SKAutoCanvasRestore(canvas, true))
-			{
-				// start drawing
-				OnPaintSurface(new SKPaintGLSurfaceEventArgs(surface, renderTarget, surfaceOrigin, colorType, glInfo));
+				// reset the args
+				lastPaintEventArgs = null;
 			}
 
+			// start drawing
+			if (!reusePaintEventArgsInstance || lastPaintEventArgs == null)
+				lastPaintEventArgs = new SKPaintGLSurfaceEventArgs(surface, renderTarget, surfaceOrigin, colorType, glInfo);
+
+			OnPaintSurface(lastPaintEventArgs);
+			canvas.RestoreToCount(0);
+
 			// update the control
 			canvas.Flush();
 			context.Flush();
@@ -97,6 +104,7 @@ protected override void OnDestroyingContext()
 		{
 			base.OnDestroyingContext();
 
+			lastPaintEventArgs = null;
 			lastSize = default;
 
 			canvas?.Dispose();