I went on with my code and realized that the problem is deeper than just asking for a new feature. The fact that there is no callback on creation means that there is no place to call any initialization from. When I create a new HtmlElementView, it's still premature to call any initialization because the actual PlatformViewLink isn't created yet, it will only come alive later in the build(), thus I can't find it in the DOM yet at that moment.

The optimal solution would be as simple as:

class HtmlElementView extends StatelessWidget {
  final String viewType;
  final PlatformViewCreatedCallback onPlatformViewCreated;
  final dynamic creationParams;

  const HtmlElementView({Key key, @required this.viewType, this.onPlatformViewCreated, this.creationParams})
      : assert(viewType != null),
        assert(kIsWeb, 'HtmlElementView is only available on Flutter Web.'),
        super(key: key);

  @override
  Widget build(BuildContext context) => PlatformViewLink(
        viewType: viewType,
        onCreatePlatformView: _createHtmlElementView,
        surfaceFactory: (BuildContext context, PlatformViewController controller) => PlatformViewSurface(
          controller: controller,
          gestureRecognizers: const <Factory<OneSequenceGestureRecognizer>>{},
          hitTestBehavior: PlatformViewHitTestBehavior.opaque,
        ),
      );

  _HtmlElementViewController _createHtmlElementView(PlatformViewCreationParams params) {
    final _HtmlElementViewController controller = _HtmlElementViewController(params.id, viewType);
    controller._initialize().then((_) {
      params.onPlatformViewCreated(params.id);
      onPlatformViewCreated(params.id); //!!!
    });
    return controller;
  }
}

In addition to the extra fields that make it on par with AndroidView and UIKitView, this actually means a single line added, marked with //!!!. It also makes way to provide the creation parameters that would be very comfortable, just like with the other platform counterparts. I don't really understand why you left that out in the first place, you had to work around this omission in your own plugins like video_player. :-)

@hterkelsen can you please triage this?

@hterkelsen It seems that something is worked on with this control (eg. PlatformViewController.clearFocus() changed to async). Couldn't this be possibly a time to check this out? It's just a simple callback providing feature parity with other platforms, nothing dangerous. :-)

Any solution for this, onPlatformViewCreated for HtmlElementView ?