fix: fix change size of canvas element.

integration_tests/specs/dom/elements/canvas/context2d.ts

@@ -1,4 +1,26 @@
 describe('Canvas context 2d', () => {
+  it('can change size by width and height property', async () => {
+    var canvas = document.createElement('canvas');
+    document.body.appendChild(canvas);
+
+    var context = canvas.getContext('2d');
+    if (!context) {
+      throw new Error('canvas context is null');
+    }
+
+    canvas.width = canvas.height = 300;
+    // Scaled rectangle
+    context.fillStyle = "red";
+    context.fillRect(10, 10, 380, 380);
+
+    await snapshot();
+    canvas.width = canvas.height = 400;
+    // Scaled rectangle
+    context.fillStyle = "red";
+    context.fillRect(10, 10, 380, 380);
+    await snapshot();
+  });
+
   it('should work with font and rect', async () => {
     var div = document.createElement('div');
     div.style.width = div.style.height = '300px';
@@ -426,7 +448,7 @@ describe('Canvas context 2d', () => {
 
     await snapshot();
   });
-  
+
   it('should work with createLinearGradient', async (done) => {
     const canvas = <canvas height="300" width="300" />;
     document.body.appendChild(canvas);

webf/example/pubspec.yaml

@@ -6,7 +6,7 @@ description: Demonstrates how to use the webf plugin.
 publish_to: 'none' # Remove this line if you wish to publish to pub.dev
 
 environment:
-  sdk: ">=2.12.0 <3.0.0"
+  sdk: ">=2.17.0 <3.0.0"
 
 dependencies:
   flutter:

webf/lib/src/bridge/native_value.dart

@@ -102,6 +102,7 @@ void toNativeValue(Pointer<NativeValue> target, value, [BindingObject? ownerBind
     target.ref.uint32 = JSPointerType.Others.index;
     target.ref.u = value.address;
   } else if (value is BindingObject) {
+    assert((value.pointer)!.address != nullptr);
     target.ref.tag = JSValueType.TAG_POINTER.index;
     target.ref.uint32 = JSPointerType.NativeBindingObject.index;
     target.ref.u = (value.pointer)!.address;

webf/lib/src/html/canvas/canvas.dart

@@ -234,10 +234,9 @@ class CanvasElement extends Element {
     // When the user agent is to set bitmap dimensions to width and height, it must run these steps:
     // 1. Reset the rendering context to its default state.
     context2d?.reset();
-    // 2. Resize the output bitmap to the new width and height and clear it to transparent black.
-    resize();
-    // 3. Let canvas be the canvas element to which the rendering context's canvas attribute was initialized.
-    // 4. If the numeric value of canvas's width content attribute differs from width,
+
+    // 2. Let canvas be the canvas element to which the rendering context's canvas attribute was initialized.
+    // 3. If the numeric value of canvas's width content attribute differs from width,
     // then set canvas's width content attribute to the shortest possible string representing width as
     // a valid non-negative integer.
     if (width != null && width.toString() != getAttribute(WIDTH)) {
@@ -251,6 +250,9 @@ class CanvasElement extends Element {
       if (height < 0) height = 0;
       internalSetAttribute(HEIGHT, height.toString());
     }
+
+    // 4. Resize the output bitmap to the new width and height and clear it to transparent black.
+    resize();
   }
 
   void _styleChangedListener(String key, String? original, String present) {