[web] fix ==/hashCode/toString for several classes across renderers (#49786)

Fix equality and hash code in `ParagraphStyle` and `StrutStyle` across renderers. Since those classes transitively rely on `Paint` and other classes, also fix those at least to a point that they pass the `test/painting/text_style_test.dart` test on the framework side.

Author: yjbanov

lib/web_ui/lib/src/engine/canvaskit/image_filter.dart

@@ -120,19 +120,6 @@ class _CkBlurImageFilter extends CkImageFilter {
     borrow(_ref.nativeObject);
   }
 
-  String get _modeString {
-    switch (tileMode) {
-      case ui.TileMode.clamp:
-        return 'clamp';
-      case ui.TileMode.mirror:
-        return 'mirror';
-      case ui.TileMode.repeated:
-        return 'repeated';
-      case ui.TileMode.decal:
-        return 'decal';
-    }
-  }
-
   @override
   bool operator ==(Object other) {
     if (runtimeType != other.runtimeType) {
@@ -149,7 +136,7 @@ class _CkBlurImageFilter extends CkImageFilter {
 
   @override
   String toString() {
-    return 'ImageFilter.blur($sigmaX, $sigmaY, $_modeString)';
+    return 'ImageFilter.blur($sigmaX, $sigmaY, ${tileModeString(tileMode)})';
   }
 }
 

lib/web_ui/lib/src/engine/canvaskit/painting.dart

@@ -296,6 +296,85 @@ class CkPaint implements ui.Paint {
   void dispose() {
     _ref.dispose();
   }
+
+  // Must be kept in sync with the default in paint.cc.
+  static const double _kStrokeMiterLimitDefault = 4.0;
+
+  // Must be kept in sync with the default in paint.cc.
+  static const int _kColorDefault = 0xFF000000;
+
+  // Must be kept in sync with the default in paint.cc.
+  static final int _kBlendModeDefault = ui.BlendMode.srcOver.index;
+
+  @override
+  String toString() {
+    String resultString = 'Paint()';
+
+    assert(() {
+      final StringBuffer result = StringBuffer();
+      String semicolon = '';
+      result.write('Paint(');
+      if (style == ui.PaintingStyle.stroke) {
+        result.write('$style');
+        if (strokeWidth != 0.0) {
+          result.write(' ${strokeWidth.toStringAsFixed(1)}');
+        } else {
+          result.write(' hairline');
+        }
+        if (strokeCap != ui.StrokeCap.butt) {
+          result.write(' $strokeCap');
+        }
+        if (strokeJoin == ui.StrokeJoin.miter) {
+          if (strokeMiterLimit != _kStrokeMiterLimitDefault) {
+            result.write(' $strokeJoin up to ${strokeMiterLimit.toStringAsFixed(1)}');
+          }
+        } else {
+          result.write(' $strokeJoin');
+        }
+        semicolon = '; ';
+      }
+      if (!isAntiAlias) {
+        result.write('${semicolon}antialias off');
+        semicolon = '; ';
+      }
+      if (color != const ui.Color(_kColorDefault)) {
+        result.write('$semicolon$color');
+        semicolon = '; ';
+      }
+      if (blendMode.index != _kBlendModeDefault) {
+        result.write('$semicolon$blendMode');
+        semicolon = '; ';
+      }
+      if (colorFilter != null) {
+        result.write('${semicolon}colorFilter: $colorFilter');
+        semicolon = '; ';
+      }
+      if (maskFilter != null) {
+        result.write('${semicolon}maskFilter: $maskFilter');
+        semicolon = '; ';
+      }
+      if (filterQuality != ui.FilterQuality.none) {
+        result.write('${semicolon}filterQuality: $filterQuality');
+        semicolon = '; ';
+      }
+      if (shader != null) {
+        result.write('${semicolon}shader: $shader');
+        semicolon = '; ';
+      }
+      if (imageFilter != null) {
+        result.write('${semicolon}imageFilter: $imageFilter');
+        semicolon = '; ';
+      }
+      if (invertColors) {
+        result.write('${semicolon}invert: $invertColors');
+      }
+      result.write(')');
+      resultString = result.toString();
+      return true;
+    }());
+
+    return resultString;
+  }
 }
 
 final Float32List _invertColorMatrix = Float32List.fromList(const <double>[

lib/web_ui/lib/src/engine/canvaskit/shader.dart

@@ -54,6 +54,9 @@ abstract class SimpleCkShader implements CkShader {
   void dispose() {
     _ref.dispose();
   }
+
+  @override
+  String toString() => 'Gradient()';
 }
 
 class CkGradientSweep extends SimpleCkShader implements ui.Gradient {
@@ -133,6 +136,9 @@ class CkGradientLinear extends SimpleCkShader implements ui.Gradient {
       matrix4 != null ? toSkMatrixFromFloat32(matrix4!) : null,
     );
   }
+
+  @override
+  String toString() => 'Gradient()';
 }
 
 class CkGradientRadial extends SimpleCkShader implements ui.Gradient {
@@ -161,6 +167,9 @@ class CkGradientRadial extends SimpleCkShader implements ui.Gradient {
       0,
     );
   }
+
+  @override
+  String toString() => 'Gradient()';
 }
 
 class CkGradientConical extends SimpleCkShader implements ui.Gradient {