Text Rendering Bug in Flutter Web (WASM) — Dart 3.8.1

[UsamaSarwar]

🔍 Description

When running a Flutter Web app using WASM and Dart SDK 3.8.1, text gets scrambled or distorted during rendering. This was not an issue in Dart 3.8.0.

📷 Screenshot

Example of garbled text while showing update progress. Letters get misaligned and spacing breaks randomly.

✅ Working Dart Version

Dart Version	Status
3.8.0	✅ Works fine
3.8.1	❌ Text scrambling occurs

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🧪 Reproduction Steps

1. Create a Flutter Web app using the stable channel (Flutter 3.32.5, Dart 3.8.1).

2. Use any Text() widget with a TextStyle inside a layout (e.g., Column/Container).

3. Run the app using flutter run -d chrome --wasm.

4. Observe the scrambled characters.

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🧰 Environment

[✓] Flutter (Channel stable, 3.32.5, on macOS 26.0 25A5295e darwin-arm64, locale en-PK)
    • Flutter version 3.32.5 on channel stable at /Library/Developer/flutter
    • Framework revision fcf2c11572 (2025-06-24)
    • Engine revision dd93de6fb1
    • Dart version 3.8.1
    • DevTools version 2.45.1
[✓] Chrome - develop for the web
    • Chrome 138.0.7204.50
[✓] macOS (desktop)
    • macOS 26.0 25A5295e darwin-arm64
[✓] Connected devices (3 available)

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🔁 Workaround

Downgrading Dart to 3.8.0 fixes the issue.

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🙏 Request

Please investigate if recent changes in Dart 3.8.1 or CanvasKit/WASM rendering could have caused this font/text layout issue.

[kevmoo]

This should likely be filed under the Flutter repository - https://github.com/flutter/flutter/

But thanks for the detailed report!

[UsamaSarwar]

Thanks for the clarification!

I’ve now filed the issue in the Flutter repo here as well: flutter/flutter#171598

Since the issue appears only with Dart 3.8.1 (and not 3.8.0), I initially suspected it might be Dart-related. But I agree — it makes sense to track it under Flutter.

Appreciate your time!

[kevmoo]

That should align with a new Flutter version as well, though, correct?

[osa1]

I'm confused -- the linked issue in Flutter looks nothing like this issue.

This issue is about a rendering bug.

The linked flutter issue is about SEO support.

@UsamaSarwar did you paste a wrong link maybe?

Regardless, closing as this should be debugged in Flutter first.