[SKIA] Don't skip setting SKCanvas.TotalMatrix when we aren't sure what the current transform is due to Save/Restore calls (#15027)

src/Skia/Avalonia.Skia/DrawingContextImpl.cs

@@ -30,7 +30,7 @@ namespace Avalonia.Skia
         private readonly Matrix? _postTransform;
         private double _currentOpacity = 1.0f;
         private readonly bool _disableSubpixelTextRendering;
-        private Matrix _currentTransform;
+        private Matrix? _currentTransform;
         private bool _disposed;
         private GRContext? _grContext;
         public GRContext? GrContext => _grContext;
@@ -466,7 +466,7 @@ namespace Avalonia.Skia
                             Transform = oldTransform;
                         }
 
-                        Canvas.Restore();
+                        RestoreCanvas();
                     }
                 }
             }
@@ -509,7 +509,7 @@ namespace Avalonia.Skia
                         using (var outerRRect = new SKRoundRect(outerRect))
                             Canvas.DrawRoundRectDifference(outerRRect, shadowRect, shadow.Paint);
                         Transform = oldTransform;
-                        Canvas.Restore();
+                        RestoreCanvas();
                         SKRoundRectCache.Shared.Return(shadowRect);
                     }
                 }
@@ -672,11 +672,17 @@ namespace Avalonia.Skia
             Canvas.ClipRegion(r);
         }
 
+        private void RestoreCanvas()
+        {
+            _currentTransform = null;
+            Canvas.Restore();
+        }
+        
         /// <inheritdoc />
         public void PopClip()
         {
             CheckLease();
-            Canvas.Restore();
+            RestoreCanvas();
         }
 
         public void PushLayer(Rect bounds)
@@ -688,7 +694,7 @@ namespace Avalonia.Skia
         public void PopLayer()
         {
             CheckLease();
-            Canvas.Restore();
+            RestoreCanvas();
         }
 
         /// <inheritdoc />
@@ -731,7 +737,7 @@ namespace Avalonia.Skia
 
             if (useOpacitySaveLayer)
             {
-                Canvas.Restore();
+                RestoreCanvas();
             }
 
             _currentOpacity = _opacityStack.Pop();
@@ -796,7 +802,7 @@ namespace Avalonia.Skia
         public void PopGeometryClip()
         {
             CheckLease();
-            Canvas.Restore();
+            RestoreCanvas();
         }
 
         /// <inheritdoc />
@@ -829,15 +835,15 @@ namespace Avalonia.Skia
             // Return the paint wrapper's paint less the reset since the paint is already reset in the Dispose method above.
             SKPaintCache.Shared.Return(paintWrapper.Paint);
 
-            Canvas.Restore();
+            RestoreCanvas();
 
-            Canvas.Restore();
+            RestoreCanvas();
         }
 
         /// <inheritdoc />
         public Matrix Transform
         {
-            get { return _currentTransform; }
+            get { return _currentTransform ??= Canvas.TotalMatrix.ToAvaloniaMatrix(); }
             set
             {
                 CheckLease();

src/Skia/Avalonia.Skia/SkiaSharpExtensions.cs

@@ -124,6 +124,11 @@ namespace Avalonia.Skia
             return sm;
         }
 
+        internal static Matrix ToAvaloniaMatrix(this SKMatrix m) => new(
+            m.ScaleX, m.SkewY, m.Persp0,
+            m.SkewX, m.ScaleY, m.Persp1,
+            m.TransX, m.TransY, m.Persp2);
+
         public static SKColor ToSKColor(this Color c)
         {
             return new SKColor(c.R, c.G, c.B, c.A);