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[Windows] Impeller windows bug: lines not anti-aliased #190392
Description
Steps to reproduce
- Create an app that draws lines (e.g., with
CustomPainterand acanvas.drawLine()) - Verify that it looks okay in non-impeller version of Flutter
- Try to run with impeller enabled (soon-to-be default)
Expected results
Lines are anti-aliased:
Actual results
Lines are seemingly rendered without anti-aliasing:
Code sample
Code sample
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(home: const MyHomePage());
}
}
class MyHomePage extends StatelessWidget {
const MyHomePage({super.key});
@override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: Colors.black,
body: SizedBox.expand(
child: Column(
mainAxisAlignment: .center,
children: [
Column(
children: [
CustomPaint(
painter: _DiagonalLinePainter(),
child: SizedBox(width: 200, height: 30),
),
],
),
],
),
),
);
}
}
class _DiagonalLinePainter extends CustomPainter {
@override
void paint(Canvas canvas, Size size) {
final paint = Paint()
..style = .stroke
..strokeWidth = 0.5
..color = Colors.white;
canvas.drawLine(Offset(0, size.height), Offset(size.width, 0), paint);
}
@override
bool shouldRepaint(_DiagonalLinePainter oldDelegate) => true;
}
Screenshots or Video
Screenshots / Video demonstration
Logs
Logs
[Paste your logs here]Flutter Doctor output
Doctor output
flutter doctor -v
[√] Flutter (Channel beta, 3.47.0-0.3.pre, on Microsoft Windows [Version 10.0.26200.8894], locale en-US)
[273ms]
• Flutter version 3.47.0-0.3.pre on channel beta at C:\src\flutter
• Upstream repository https://github.com/flutter/flutter.git
• Framework revision 7c7929adb0 (2 days ago), 2026-07-29 21:46:53 -0700
• Engine revision effb186f31
• Dart version 3.13.0 (build 3.13.0-282.3.beta)
• DevTools version 2.59.0
• Feature flags: enable-web, enable-linux-desktop, enable-macos-desktop, enable-windows-desktop,
enable-android, enable-ios, cli-animations, enable-native-assets, enable-record-use,
enable-swift-package-manager, omit-legacy-version-file, enable-lldb-debugging,
enable-uiscene-migration
[√] Windows Version (11 Pro 64-bit, 25H2, 2009) [830ms]
[!] Android toolchain - develop for Android devices (Android SDK version 34.0.0) [2.2s]
• Android SDK at C:\Users\filip\AppData\Local\Android\sdk
• Emulator version 32.1.15.0 (build_id 10696886) (CL:N/A)
X Flutter requires Android SDK 36 and the Android BuildTools 28.0.3
To update the Android SDK visit https://flutter.dev/to/windows-android-setup for detailed
instructions.
! Some Android licenses not accepted. To resolve this, run: flutter doctor --android-licenses
[√] Chrome - develop for the web [110ms]
• Chrome at C:\Program Files (x86)\Google\Chrome\Application\chrome.exe
[√] Visual Studio - develop Windows apps (Visual Studio Build Tools 2022 17.12.3) [109ms]
• Visual Studio at C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools
• Visual Studio Build Tools 2022 version 17.12.35527.113
• Windows 10 SDK version 10.0.19041.0
[√] Connected device (3 available) [152ms]
• Windows (desktop) • windows • windows-x64 • Microsoft Windows [Version 10.0.26200.8894]
• Chrome (web) • chrome • web-javascript • Google Chrome 150.0.7871.114
• Edge (web) • edge • web-javascript • Microsoft Edge 150.0.4078.48
[√] Network resources [567ms]
• All expected network resources are available.
! Doctor found issues in 1 category.
Activity
filiph commentedon Aug 1, 2026
It seems as if there's some cut-off so that lines can completely disappear if they happen to be at exactly the wrong position.
No impeller:
Impeller:
Razorex001 commentedon Aug 1, 2026
The antialiased lines issue should be #189827 which has been fixed on channel master, (I tested the antialsiasing on windows with Flutter 3.47.0-1.0.pre-322 • channel master, and the issue was not visible there. Not sure when the fix will get merged into beta.
The lines disappearing, I don't know. It may be a different issue.
@filiph Could you test these issues (together with the font rendering issue that you wrote for #190391 ) on latest channel master version?
filiph commentedon Aug 1, 2026
Running on
mastershows a blank screen:Razorex001 commentedon Aug 1, 2026
@filiph , your master version is 8 months old. Please upgrade to latest channel master version.
I have tried to reproduce the issue with the code you provided, but I was not able to. On my end everything looks good.
The only difference I notice is that Impeller seems to draw that line a bit thicker or somewhat slightly more visible than Skia.
See the screenshots:
Skia:
Impeller:
filiph commentedon Aug 1, 2026
🤦 Thanks for spotting that. I'm not using Windows that often, clearly.
Yes, on
master, anti-aliasing is back. It's different, and as @Razorex001 says, slightly more visible. But it's obviously much better than the non-anti-aliased version on currentbeta.filiph commentedon Aug 1, 2026
And yes, the horizontal lines issue seems to be the same issue.
Impeller on beta:
Impeller on master:
So I'm guessing we can close this issue, unless it's needed as a backing for some cherry pick discussion or something.
b-luk commentedon Aug 3, 2026
Thanks for the report and resolution, Filip and Razorex001. We did recently do a bunch of improvements to thin line rendering on Impeller, so we're hoping things look good now.
In our fixes, we prioritized correctness and consistency rather than simply trying to reproduce what Skia renders. As you noticed, diagonal lines are slightly more visible on Impeller compared to Skia. Two specific differences that I'll highlight, which I think are improvements over Skia:
If this doesn't seem to match what you see, or you notice any visual inaccuracies with lines, please file new issues and I will take a look.
filiph commentedon Aug 3, 2026
This is fantastic, I'm very happy. Thank you!
github-actions commentedon Aug 17, 2026
This thread has been automatically locked since there has not been any recent activity after it was closed. If you are still experiencing a similar issue, please open a new bug, including the output of
flutter doctor -vand a minimal reproduction of the issue.