Flutter web × Android WebView — minimal reproduction

Small Flutter web app (CanvasKit) for reporting issues to flutter/flutter.

Live demo: https://hunghd.dev/flutter_web_embedding_issue/
Mirror: https://hnvn.github.io/flutter_web_embedding_issue/

What it shows

1. Blank CJK Text in Android WebView (space reserved, glyphs missing)
2. Incomplete RepaintBoundary.toImage() for off-screen widgets
3. Expanded reports maxHeight: 0 inside a bounded Column

Same URL works in Chrome on the device; fails in embedded WebView (; wv) user agent).

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Build

flutter pub get
bash scripts/build_web.sh
# output: build/web

Serve build/web over HTTPS, or push to main to deploy via GitHub Actions (see .github/workflows/deploy-pages.yml).

GitHub Pages (one-time): repo Settings → Pages → Source: GitHub Actions.

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Test in Android WebView

1. Open the live demo in Chrome on the phone (baseline).
2. Open the same URL in any Android WebView shell.
3. Compare: scroll behavior, Japanese text, Expanded probe (green vs red), capture preview.

Remote debug: chrome://inspect → select the WebView → Console.

Example (generic WebView app via adb):

adb shell am start -a android.intent.action.VIEW \
  -d 'https://hunghd.dev/flutter_web_embedding_issue/'

(Use whatever WebView host app you have; the repro URL is all that matters.)

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Source

Standalone repo: https://github.com/hnvn/flutter_web_embedding_issue