[impeller] Inconsistent size and result on fragment shaders #132802
Description
Steps to reproduce
Run the code sample in iOS vs macOS, or a regular iOS run vs flutter run --no-enable-impeller
Expected results
Note the vertical red bar position, the shader generated gradient should have the same size in both impeller vs non-impeller.
Actual results
Different results in iOS impeller vs non-impeller (also couldn't run it at all in macOS/Android with flutter run --enable-impeller to test macOS version of impeller for this issue which is a separate bug also)
Code sample
Code sample
import 'dart:ui';
import 'package:flutter/material.dart';
void main() {
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({super.key});
@override
Widget build(BuildContext context) {
return MaterialApp(
theme: ThemeData(useMaterial3: true),
home: const ShaderPage(),
);
}
}
class ShaderPage extends StatefulWidget {
const ShaderPage({super.key});
@override
State<ShaderPage> createState() => _ShaderPageState();
}
class _ShaderPageState extends State<ShaderPage> {
bool _initialized = false;
FragmentProgram? _shader;
void _initializeShader() async {
if (_initialized == true) return;
_initialized = true;
final shader = await FragmentProgram.fromAsset('shaders/shader.frag');
setState(() => _shader = shader);
}
@override
Widget build(BuildContext context) {
_initializeShader();
final shader = _shader;
return Scaffold(
appBar: AppBar(title: const Text('Test')),
body: SingleChildScrollView(
child: Column(
children: [
if (shader != null)
CustomPaint(
painter: _ScenePainter(shader),
child: Padding(
padding: const EdgeInsets.only(top: 8, bottom: 8),
child: Stack(
children: [
Container(height: 200),
Container(height: 200, width: 10, color: Colors.red),
],
),
),
),
Container(height: 1800),
],
),
),
);
}
}
class _ScenePainter extends CustomPainter {
final FragmentProgram program;
_ScenePainter(this.program);
@override
void paint(Canvas canvas, Size size) {
final shader = program.fragmentShader();
shader.setFloat(0, size.width);
shader.setFloat(1, size.height);
canvas.drawPaint(Paint()..shader = shader);
}
@override
bool shouldRepaint(covariant CustomPainter oldDelegate) => true;
}And save the following in shaders/shader.frag
#include <flutter/runtime_effect.glsl>
uniform vec2 uSize;
out vec4 fragColor;
void main() {
float v = FlutterFragCoord().y / uSize.y;
fragColor = vec4(v, v, v, 1);
}And add the following to pubspec.yaml,
flutter:
[...]
shaders:
- shaders/shader.frag
Screenshots or Video
Screenshots / Video demonstration
regular macOS run vs regular [impeller] iOS run:
regular macOS run vs no-impeller iOS run (flutter run --no-enable-impeller):
Logs
No response
Flutter Doctor output
Doctor output
flutter doctor -v
[✓] Flutter (Channel stable, 3.13.0, on macOS 13.4.1 22F770820d darwin-arm64,
locale en-US)
• Flutter version 3.13.0 on channel stable at /Users/ebrahim/flutter
• Upstream repository https://github.com/flutter/flutter.git
• Framework revision efbf63d9c6 (2 days ago), 2023-08-15 21:05:06 -0500
• Engine revision 1ac611c64e
• Dart version 3.1.0
• DevTools version 2.25.0
[✓] Android toolchain - develop for Android devices (Android SDK version 33.0.2)
• Android SDK at /Users/ebrahim/Library/Android/sdk
• Platform android-34, build-tools 33.0.2
• Java binary at: /Applications/Android
Studio.app/Contents/jbr/Contents/Home/bin/java
• Java version OpenJDK Runtime Environment (build
17.0.6+0-17.0.6b829.9-10027231)
• All Android licenses accepted.
[✓] Xcode - develop for iOS and macOS (Xcode 14.3.1)
• Xcode at /Applications/Xcode.app/Contents/Developer
• Build 14E300c
• CocoaPods version 1.11.3
[✓] Chrome - develop for the web
• Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome
[✓] Android Studio (version 2022.3)
• Android Studio at /Applications/Android Studio.app/Contents
• Flutter plugin can be installed from:
🔨 https://plugins.jetbrains.com/plugin/9212-flutter
• Dart plugin can be installed from:
🔨 https://plugins.jetbrains.com/plugin/6351-dart
• Java version OpenJDK Runtime Environment (build
17.0.6+0-17.0.6b829.9-10027231)
[✓] VS Code (version 1.81.1)
• VS Code at /Applications/Visual Studio Code.app/Contents
• Flutter extension version 3.70.0
[✓] Connected device (3 available)
• iPad Pro (12.9-inch) (6th generation) (mobile) •
14D51279-7D96-4D91-B7FA-5F3BCA78F1C3 • ios •
com.apple.CoreSimulator.SimRuntime.iOS-16-4 (simulator)
• macOS (desktop) • macos
• darwin-arm64 • macOS 13.4.1 22F770820d darwin-arm64
• Chrome (web) • chrome
• web-javascript • Google Chrome 114.0.5735.198
[✓] Network resources
• All expected network resources are available.
• No issues found!