fix stability of wasm init.

src/Web/Avalonia.Web.Blazor/AvaloniaView.razor.cs

@@ -287,17 +287,22 @@ namespace Avalonia.Web.Blazor
 
                 _topLevelImpl.SetSurface(_context, _jsGlInfo, ColorType,
                     new PixelSize((int)_canvasSize.Width, (int)_canvasSize.Height), _dpi);
+                
+                _interop.SetCanvasSize((int)(_canvasSize.Width * _dpi), (int)(_canvasSize.Height * _dpi));
 
                 _initialised = true;
 
-                _topLevel.Prepare();
-
-                _topLevel.Renderer.Start();
-
-                Invalidate();
-
-                _sizeWatcher = await SizeWatcherInterop.ImportAsync(Js, _htmlCanvas, OnSizeChanged);
-                _dpiWatcher = await DpiWatcherInterop.ImportAsync(Js, OnDpiChanged);
+                Threading.Dispatcher.UIThread.Post(async () =>
+                {
+                    _interop.RequestAnimationFrame(true);
+                    
+                    _sizeWatcher = await SizeWatcherInterop.ImportAsync(Js, _htmlCanvas, OnSizeChanged);
+                    _dpiWatcher = await DpiWatcherInterop.ImportAsync(Js, OnDpiChanged);
+                    
+                    _topLevel.Prepare();
+
+                    _topLevel.Renderer.Start();
+                });
             }
         }
 
@@ -336,37 +341,30 @@ namespace Avalonia.Web.Blazor
 
         private void OnDpiChanged(double newDpi)
         {
-            _dpi = newDpi;
+            if (Math.Abs(_dpi - newDpi) > 0.0001)
+            {
+                _dpi = newDpi;
+
+                _interop.SetCanvasSize((int)(_canvasSize.Width * _dpi), (int)(_canvasSize.Height * _dpi));
 
-            _topLevelImpl.SetClientSize(_canvasSize, _dpi);
-            
-            ForceBlit();
+                _topLevelImpl.SetClientSize(_canvasSize, _dpi);
 
-            Invalidate();
+                ForceBlit();
+            }
         }
 
         private void OnSizeChanged(SKSize newSize)
         {
-            _canvasSize = newSize;
-            
-            _interop.SetCanvasSize((int)(_canvasSize.Width * _dpi), (int)(_canvasSize.Height * _dpi));
-
-            _topLevelImpl.SetClientSize(_canvasSize, _dpi);
+            if (_canvasSize != newSize)
+            {
+                _canvasSize = newSize;
 
-            ForceBlit();
+                _interop.SetCanvasSize((int)(_canvasSize.Width * _dpi), (int)(_canvasSize.Height * _dpi));
 
-            Invalidate();
-        }
+                _topLevelImpl.SetClientSize(_canvasSize, _dpi);
 
-        public void Invalidate()
-        {
-            if (!_initialised || _jsGlInfo == null)
-            {
-                Console.WriteLine("invalidate ignored");
-                return;
+                ForceBlit();
             }
-
-            _interop.RequestAnimationFrame(true);
         }
 
         public void SetActive(bool active)