[web] Pass creation params to the platform view factory (#128146)
This concludes step 1 of the `HtmlElementView` improvements. It's now possible to pass creation params to platform view factories directly from `HtmlElementView`.
Here's a sample app using a single factory to render platform views in different colors:
<details>
<summary>Code sample</summary>
```dart
import 'dart:js_interop';
import 'dart:ui_web' as ui_web;
import 'package:flutter/material.dart';
import 'package:web/web.dart' as web;
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Platform View Demo',
home: Scaffold(
appBar: AppBar(
title: Text('Platform View Demo'),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: [
BoxWrapper('red'),
BoxWrapper(null),
BoxWrapper('blue'),
],
),
),
),
);
}
}
bool isRegistered = false;
class BoxWrapper extends StatelessWidget {
const BoxWrapper(this.cssColor);
final String? cssColor;
void register() {
if (isRegistered) return;
isRegistered = true;
ui_web.platformViewRegistry.registerViewFactory('my-platform-view', (
id, {
Object? params,
}) {
params as String?;
final element = web.document.createElement('div'.toJS) as web.HTMLElement;
element.textContent = 'Platform View'.toJS;
element.style
..lineHeight = '100px'.toJS
..fontSize = '24px'.toJS
..backgroundColor = (params ?? 'pink').toJS
..textAlign = 'center'.toJS;
return element;
});
}
@override
Widget build(BuildContext context) {
register();
return SizedBox(
width: 200,
height: 100,
child: Card(
child: HtmlElementView(
viewType: 'my-platform-view',
creationParams: cssColor,
),
),
);
}
}
```
</details>
Depends on https://github.com/flutter/engine/pull/42255
Part of https://github.com/flutter/flutter/issues/127030
b0188cd182