Path.combine not implemented in the HTML backend #44572
Description
this code below works fine on flutter mobile
but on web it throws an error
import 'package:flutter/material.dart';
void main() => runApp(App());
class App extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
home: Scaffold(
body: SafeArea(
child: Center(
child: Column(
mainAxisSize: MainAxisSize.min,
children: <Widget>[
UnicornOutlineButton(
strokeWidth: 2,
radius: 24,
gradient: LinearGradient(colors: [Colors.black, Colors.redAccent]),
child: Text('OMG', style: TextStyle(fontSize: 16)),
onPressed: () {},
),
SizedBox(width: 0, height: 24),
UnicornOutlineButton(
strokeWidth: 4,
radius: 16,
gradient: LinearGradient(
colors: [Colors.blue, Colors.yellow],
begin: Alignment.topCenter,
end: Alignment.bottomCenter,
),
child: Text('Wow', style: TextStyle(fontSize: 16)),
onPressed: () {},
),
],
),
),
),
),
);
}
}
class UnicornOutlineButton extends StatelessWidget {
final _GradientPainter _painter;
final Widget _child;
final VoidCallback _callback;
final double _radius;
UnicornOutlineButton({
@required double strokeWidth,
@required double radius,
@required Gradient gradient,
@required Widget child,
@required VoidCallback onPressed,
}) : this._painter = _GradientPainter(strokeWidth: strokeWidth, radius: radius, gradient: gradient),
this._child = child,
this._callback = onPressed,
this._radius = radius;
@override
Widget build(BuildContext context) {
return CustomPaint(
painter: _painter,
child: GestureDetector(
behavior: HitTestBehavior.translucent,
onTap: _callback,
child: InkWell(
borderRadius: BorderRadius.circular(_radius),
onTap: _callback,
child: Container(
constraints: BoxConstraints(minWidth: 88, minHeight: 48),
child: Row(
mainAxisSize: MainAxisSize.min,
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
_child,
],
),
),
),
),
);
}
}
class _GradientPainter extends CustomPainter {
final Paint _paint = Paint();
final double radius;
final double strokeWidth;
final Gradient gradient;
_GradientPainter({@required double strokeWidth, @required double radius, @required Gradient gradient})
: this.strokeWidth = strokeWidth,
this.radius = radius,
this.gradient = gradient;
@override
void paint(Canvas canvas, Size size) {
// create outer rectangle equals size
Rect outerRect = Offset.zero & size;
var outerRRect = RRect.fromRectAndRadius(outerRect, Radius.circular(radius));
// create inner rectangle smaller by strokeWidth
Rect innerRect = Rect.fromLTWH(strokeWidth, strokeWidth, size.width - strokeWidth * 2, size.height - strokeWidth * 2);
var innerRRect = RRect.fromRectAndRadius(innerRect, Radius.circular(radius - strokeWidth));
// apply gradient shader
_paint.shader = gradient.createShader(outerRect);
// create difference between outer and inner paths and draw it
Path path1 = Path()..addRRect(outerRRect);
Path path2 = Path()..addRRect(innerRRect);
var path = Path.combine(PathOperation.difference, path1, path2);
canvas.drawPath(path, _paint);
}
@override
bool shouldRepaint(CustomPainter oldDelegate) => oldDelegate != this;
}
here is full log
Performing hot restart...
Reloaded application in 423ms.
══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════
The following UnimplementedError was thrown during paint():
UnimplementedError
The relevant error-causing widget was:
CustomPaint org-dartlang-app:///packages/mywebapp/main.dart:64:12
When the exception was thrown, this was the stack:
package:dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart 194:49 throw_
package:build_web_compilers/lib/ui/src/ui/canvas.dart 2200:5 combine
package:mywebapp/main.dart 115:21 paint
package:flutter/src/rendering/custom_paint.dart 531:12 [_paintWithPainter]
package:flutter/src/rendering/custom_paint.dart 572:7 paint
package:flutter/src/rendering/object.dart 2211:7 [_paintWithContext]
package:flutter/src/rendering/object.dart 184:12 paintChild
package:flutter/src/rendering/box.dart 2508:14 defaultPaint
package:flutter/src/rendering/flex.dart 948:7 paint
package:flutter/src/rendering/object.dart 2211:7 [_paintWithContext]
package:flutter/src/rendering/object.dart 184:12 paintChild
package:flutter/src/rendering/shifted_box.dart 70:14 paint
package:flutter/src/rendering/object.dart 2211:7 [_paintWithContext]
package:flutter/src/rendering/object.dart 184:12 paintChild
package:flutter/src/rendering/shifted_box.dart 70:14 paint
package:flutter/src/rendering/object.dart 2211:7 [_paintWithContext]
package:flutter/src/rendering/object.dart 184:12 paintChild
package:flutter/src/rendering/box.dart 2508:14 defaultPaint
package:flutter/src/rendering/custom_layout.dart 396:5 paint
package:flutter/src/rendering/object.dart 2211:7 [_paintWithContext]
package:flutter/src/rendering/object.dart 184:12 paintChild
package:flutter/src/rendering/proxy_box.dart 123:14 paint
package:flutter/src/material/material.dart 530:11 paint
package:flutter/src/rendering/object.dart 2211:7 [_paintWithContext]
package:flutter/src/rendering/object.dart 184:12 paintChild
package:flutter/src/rendering/proxy_box.dart 123:14 paint
package:flutter/src/rendering/object.dart 384:12 pushLayer
package:flutter/src/rendering/proxy_box.dart 1757:14 paint
package:flutter/src/rendering/object.dart 2211:7 [_paintWithContext]
package:flutter/src/rendering/object.dart 184:12 paintChild
package:flutter/src/rendering/proxy_box.dart 123:14 paint
package:flutter/src/rendering/object.dart 2211:7 [_paintWithContext]
package:flutter/src/rendering/object.dart 184:12 paintChild
package:flutter/src/rendering/proxy_box.dart 123:14 paint
package:flutter/src/rendering/object.dart 2211:7 [_paintWithContext]
package:flutter/src/rendering/object.dart 135:10 _repaintCompositedChild
package:flutter/src/rendering/object.dart 95:5 repaintCompositedChild
package:flutter/src/rendering/object.dart 201:7 [_compositeChild]
package:flutter/src/rendering/object.dart 182:7 paintChild
package:flutter/src/rendering/proxy_box.dart 123:14 paint
package:flutter/src/rendering/object.dart 2211:7 [_paintWithContext]
package:flutter/src/rendering/object.dart 184:12 paintChild
package:flutter/src/rendering/proxy_box.dart 921:16 paint
package:flutter/src/rendering/object.dart 2211:7 [_paintWithContext]
package:flutter/src/rendering/object.dart 184:12 paintChild
package:flutter/src/rendering/proxy_box.dart 123:14 paint
package:flutter/src/rendering/proxy_box.dart 2464:13 paint
package:flutter/src/rendering/object.dart 2211:7 [_paintWithContext]
package:flutter/src/rendering/object.dart 184:12 paintChild
package:flutter/src/rendering/proxy_box.dart 123:14 paint
package:flutter/src/rendering/object.dart 2211:7 [_paintWithContext]
package:flutter/src/rendering/object.dart 135:10 _repaintCompositedChild
package:flutter/src/rendering/object.dart 95:5 repaintCompositedChild
package:flutter/src/rendering/object.dart 201:7 [_compositeChild]
package:flutter/src/rendering/object.dart 182:7 paintChild
package:flutter/src/rendering/proxy_box.dart 123:14 paint
package:flutter/src/rendering/object.dart 2211:7 [_paintWithContext]
package:flutter/src/rendering/object.dart 184:12 paintChild
package:flutter/src/rendering/proxy_box.dart 123:14 paint
package:flutter/src/rendering/proxy_box.dart 3174:11 paint
package:flutter/src/rendering/object.dart 2211:7 [_paintWithContext]
package:flutter/src/rendering/object.dart 184:12 paintChild
package:flutter/src/rendering/box.dart 2508:14 defaultPaint
package:flutter/src/rendering/stack.dart 589:5 paintStack
package:flutter/src/rendering/stack.dart 597:7 paint
package:flutter/src/rendering/object.dart 2211:7 [_paintWithContext]
package:flutter/src/rendering/object.dart 184:12 paintChild
package:flutter/src/rendering/proxy_box.dart 123:14 paint
package:flutter/src/rendering/object.dart 2211:7 [_paintWithContext]
package:flutter/src/rendering/object.dart 184:12 paintChild
package:flutter/src/rendering/proxy_box.dart 123:14 paint
package:flutter/src/rendering/object.dart 2211:7 [_paintWithContext]
package:flutter/src/rendering/object.dart 184:12 paintChild
package:flutter/src/rendering/proxy_box.dart 123:14 paint
package:flutter/src/rendering/object.dart 2211:7 [_paintWithContext]
package:flutter/src/rendering/object.dart 184:12 paintChild
package:flutter/src/rendering/proxy_box.dart 123:14 paint
package:flutter/src/rendering/object.dart 2211:7 [_paintWithContext]
package:flutter/src/rendering/object.dart 184:12 paintChild
package:flutter/src/rendering/proxy_box.dart 123:14 paint
package:flutter/src/rendering/object.dart 2211:7 [_paintWithContext]
package:flutter/src/rendering/object.dart 184:12 paintChild
package:flutter/src/rendering/proxy_box.dart 123:14 paint
package:flutter/src/rendering/object.dart 2211:7 [_paintWithContext]
package:flutter/src/rendering/object.dart 184:12 paintChild
package:flutter/src/rendering/view.dart 210:14 paint
package:flutter/src/rendering/object.dart 2211:7 [_paintWithContext]
package:flutter/src/rendering/object.dart 135:10 _repaintCompositedChild
package:flutter/src/rendering/object.dart 95:5 repaintCompositedChild
package:flutter/src/rendering/object.dart 937:29 flushPaint
package:flutter/src/rendering/binding.dart 346:19 drawFrame
package:flutter/src/widgets/binding.dart 774:13 drawFrame
package:flutter/src/rendering/binding.dart 283:5 [_handlePersistentFrameCallback]
package:flutter/src/scheduler/binding.dart 1101:15 [_invokeFrameCallback]
package:flutter/src/scheduler/binding.dart 1040:9 handleDrawFrame
package:flutter/src/scheduler/binding.dart 849:7 <fn>
package:dart-sdk/lib/_internal/js_dev_runtime/private/isolate_helper.dart 48:19 internalCallback
The following RenderObject was being processed when the exception was fired: RenderCustomPaint#dc268 relayoutBoundary=up4:
creator: CustomPaint ← UnicornOutlineButton ← Column ← Center ← MediaQuery ← Padding ← SafeArea ←
_BodyBuilder ← MediaQuery ← LayoutId-[<_ScaffoldSlot.body>] ← CustomMultiChildLayout ←
AnimatedBuilder ← ⋯
parentData: offset=Offset(0.0, 0.0); flex=null; fit=null (can use size)
constraints: BoxConstraints(0.0<=w<=1920.0, 0.0<=h<=Infinity)
size: Size(88.0, 48.0)
This RenderObject had the following descendants (showing up to depth 5):
child: RenderSemanticsGestureHandler#078b7 relayoutBoundary=up5 NEEDS-PAINT
child: RenderPointerListener#fd406 relayoutBoundary=up6 NEEDS-PAINT
child: RenderSemanticsAnnotations#9008b relayoutBoundary=up7 NEEDS-PAINT
child: RenderMouseRegion#dec56 relayoutBoundary=up8 NEEDS-PAINT
child: RenderSemanticsGestureHandler#cea3a relayoutBoundary=up9 NEEDS-PAINT
════════════════════════════════════════════════════════════════════════════════════════════════════
Another exception was thrown: UnimplementedError
if I commented this line, everything if ok and working fine, but I need subtract one path from another. Actually all path operations are throwing errors on flutter web.
var path = Path.combine(PathOperation.difference, path1, path2);
Tried on MAC Catalina and Windows 10.
flutter doctor -v
• Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome
[✓] Android Studio (version 3.5)
• Android Studio at /Applications/Android Studio.app/Contents
• Flutter plugin version 40.2.2
• Dart plugin version 191.8593
• Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b49-5587405)
[✓] Connected device (2 available)
• Chrome • chrome • web-javascript • Google Chrome 78.0.3904.97
• Web Server • web-server • web-javascript • Flutter Tools
• No issues found!
my original post on SO https://stackoverflow.com/questions/55395641/outlined-transparent-button-with-gradient-border-in-flutter/55638138