CustomPainter allows painting outside even if canvas.clipRect(rect) called correctly #66719
Description
On Android emulator Pixel 2 (1080 * 1920; 420 dpi; API: 29) I was able to paint outside of CustomPainter's bounds which shouldn't happen because canvas.clipRect(rect) was called with the correct size.
Minimal code to reproduce:
import 'dart:ui';
import 'package:flutter/material.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
home: HomePage(),
);
}
}
class HomePage extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text('Canvas test')),
body: Padding(
padding: EdgeInsets.all(40.0),
child: Container(
decoration: BoxDecoration(
border: Border.all(
color: Colors.black,
width: 1.0,
),
),
child: LayoutBuilder(
builder: (BuildContext context, BoxConstraints bc) {
final size = Size(bc.maxWidth, bc.maxHeight);
return CustomPaint(
painter: TestPainter(),
size: size,
);
},
),
),
),
);
}
}
class TestPainter extends CustomPainter {
@override
void paint(Canvas canvas, Size size) {
final rect = Offset.zero & size;
canvas.clipRect(rect);
final paint = Paint();
paint
..style = PaintingStyle.fill
..color = Colors.red;
paint.strokeWidth = 3.0;
var offsets = [
Offset(rect.width - 30, rect.height / 2),
Offset(rect.width + 30, rect.height / 2),
Offset(rect.width + 30, rect.height / 2 + 60),
Offset(rect.width - 30, rect.height / 2 + 60),
];
canvas.drawPoints(PointMode.points, [...offsets, offsets[0]], paint);
}
@override
bool shouldRepaint(CustomPainter oldDelegate) {
return false;
}
}Result:
Result if canvas.clipRect(rect); commented out (which is correct):
If I change PointMode.lines to PointMode.polygon
If I change PointMode.lines to PointMode.polygon and comment out paint.strokeWidth = 3.0; then everything works fine, I think strokeWidth ruins the whole thing.
flutter doctor
[√] Flutter (Channel stable, 1.20.4, on Microsoft Windows [Version 10.0.18363.1082], locale hu-HU)
• Flutter version 1.20.4 at C:\flutter
• Framework revision fba99f6cf9 (11 days ago), 2020-09-14 15:32:52 -0700
• Engine revision d1bc06f032
• Dart version 2.9.2
[√] Android toolchain - develop for Android devices (Android SDK version 30.0.1)
• Android SDK at C:\Users\maRci002\AppData\Local\Android\Sdk
• Platform android-30, build-tools 30.0.1
• ANDROID_HOME = C:\Users\maRci002\AppData\Local\Android\Sdk
• Java binary at: C:\Program Files\Android\Android Studio\jre\bin\java
• Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b01)
• All Android licenses accepted.
[√] Android Studio (version 4.0)
• Android Studio at C:\Program Files\Android\Android Studio
• Flutter plugin version 49.0.2
• Dart plugin version 193.7547
• Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b01)
[√] Connected device (1 available)
• Android SDK built for x86 (mobile) • emulator-5554 • android-x86 • Android 10 (API 29) (emulator)
• No issues found!