Add bridgeEvents API and typed JavaScript handler helpers (additive, cross-platform)

[parkwoocheol]

Is there an existing feature request for this?

• I have searched the existing feature request

Operating System

All platforms if possible: Android, iOS, macOS, Windows, Linux, Web (same-origin constraints on Web).

Pain

Current JavaScript communication APIs are powerful, but common app flows still require repetitive low-level code:

• Dart -> JS push-style messaging is usually done with manual evaluateJavascript.
• JS handler payloads often require manual JSON parsing/encoding in app code.
• Event-style communication patterns are not standardized at the controller API level.
• Cross-platform app code becomes verbose and easier to break with custom bridge boilerplate.

This increases complexity for users who need structured, bidirectional JS communication.

Suggested solution

Add an additive high-level JS bridge layer without changing existing behavior:

1. controller.bridgeEvents API

• on(eventName, callback)
• off(eventName, [callback])
• emit(eventName, data)
• hasListener(eventName)

2. Typed handler helper APIs

• addSerializedJavaScriptHandler<TRequest, TResponse>(...)
• addJsonJavaScriptHandler<TRequest, TResponse>(...)

Design constraints:

• No breaking changes to existing addJavaScriptHandler behavior.
• Keep existing bridge security model and allowlist behavior unchanged.
• Do not hardcode bridge global name; use runtime bridge name.
• Implement for all active platform bridge initialization paths to keep API consistency.

Acceptance criteria:

• Existing apps continue to work unchanged.
• New APIs are fully additive.
• Example + integration tests cover bridgeEvents and typed handler roundtrip.

Useful resources

• JS communication docs:
  • https://inappwebview.dev/docs/webview/javascript/communication/
• User scripts docs:
  • https://inappwebview.dev/docs/webview/javascript/user-scripts/
• Content worlds docs:
  • https://inappwebview.dev/docs/webview/javascript/content-worlds/
• JS injection docs:
  • https://inappwebview.dev/docs/webview/javascript/injection/
• API docs:
  • https://pub.dev/documentation/flutter_inappwebview/latest/flutter_inappwebview/
• Reference design direction:
  • https://github.com/parkwoocheol/compose-webview

Additional information

I can implement this in a feature branch and open a PR with:

• platform-consistent bridge wiring
• backward-compatibility checks
• example coverage
• integration tests

Self grab

• I'm ready to work on this issue!