Return an empty surface in case the allocation has failed (#1784)

Co-authored-by: Richirisu <[email protected]>
Co-authored-by: Matthew Leibowitz <[email protected]>

source/SkiaSharp.Views.Uno/SkiaSharp.Views.Uno.iOS/SKXamlCanvas.iOS.cs

@@ -46,5 +46,19 @@ public override void Draw(CGRect dirtyRect)
 			// draw the surface to the context
 			drawable.DrawSurface(ctx, Bounds, info, surface);
 		}
+
+		public override void WillMoveToWindow(UIWindow window)
+		{
+			if (drawable != null)
+			{
+				// release the memory if we are leaving the window
+				if (window == null)
+					drawable?.Dispose();
+				else
+					SetNeedsDisplay();
+			}
+
+			base.WillMoveToWindow(window);
+		}
 	}
 }

source/SkiaSharp.Views/SkiaSharp.Views.Apple/SKCGSurfaceFactory.cs

@@ -47,6 +47,15 @@ public SKSurface CreateSurface(CGRect contentsBounds, nfloat scale, out SKImageI
 			if (bitmapData == null)
 			{
 				bitmapData = NSMutableData.FromLength(info.BytesSize);
+
+				// in case allocation has failed
+				if (bitmapData == null)
+				{
+					Dispose();
+					info = Info;
+					return null;
+				}
+
 				dataProvider = new CGDataProvider(bitmapData.MutableBytes, info.BytesSize, Dummy);
 
 				void Dummy(IntPtr data)

source/SkiaSharp.Views/SkiaSharp.Views.AppleiOS/SKCanvasView.cs

@@ -105,6 +105,20 @@ public override void Draw(CGRect rect)
 			}
 		}
 
+		public override void WillMoveToWindow(UIWindow window)
+		{
+			if (drawable != null)
+			{
+				// release the memory if we are leaving the window
+				if (window == null)
+					drawable?.Dispose();
+				else
+					SetNeedsDisplay();
+			}
+
+			base.WillMoveToWindow(window);
+		}
+
 		public event EventHandler<SKPaintSurfaceEventArgs> PaintSurface;
 
 		protected virtual void OnPaintSurface(SKPaintSurfaceEventArgs e)