[web] Support platform view creation params

lib/web_ui/lib/src/engine/platform_views/content_manager.dart

@@ -2,25 +2,14 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'package:ui/ui_web/src/ui_web.dart' as ui_web;
+
 import '../browser_detection.dart';
 import '../dom.dart';
 import '../embedder.dart';
 import '../util.dart';
 import 'slots.dart';
 
-/// A function which takes a unique `id` and some `params` and creates an HTML element.
-///
-/// This is made available to end-users through dart:ui in web.
-typedef ParameterizedPlatformViewFactory = DomElement Function(
-  int viewId, {
-  Object? params,
-});
-
-/// A function which takes a unique `id` and creates an HTML element.
-///
-/// This is made available to end-users through dart:ui in web.
-typedef PlatformViewFactory = DomElement Function(int viewId);
-
 /// This class handles the lifecycle of Platform Views in the DOM of a Flutter Web App.
 ///
 /// There are three important parts of Platform Views. This class manages two of
@@ -79,8 +68,13 @@ class PlatformViewManager {
   /// `factoryFunction` needs to be a [PlatformViewFactory].
   bool registerFactory(String viewType, Function factoryFunction,
       {bool isVisible = true}) {
-    assert(factoryFunction is PlatformViewFactory ||
-        factoryFunction is ParameterizedPlatformViewFactory);
+    assert(
+      factoryFunction is ui_web.PlatformViewFactory ||
+          factoryFunction is ui_web.ParameterizedPlatformViewFactory,
+      'Factory signature is invalid. Expected either '
+      '{${ui_web.PlatformViewFactory}} or {${ui_web.ParameterizedPlatformViewFactory}} '
+      'but got: {${factoryFunction.runtimeType}}',
+    );
 
     if (_factories.containsKey(viewType)) {
       return false;
@@ -132,11 +126,11 @@ class PlatformViewManager {
       final Function factoryFunction = _factories[viewType]!;
       final DomElement content;
 
-      if (factoryFunction is ParameterizedPlatformViewFactory) {
-        content = factoryFunction(viewId, params: params);
+      if (factoryFunction is ui_web.ParameterizedPlatformViewFactory) {
+        content = factoryFunction(viewId, params: params) as DomElement;
       } else {
-        factoryFunction as PlatformViewFactory;
-        content = factoryFunction(viewId);
+        factoryFunction as ui_web.PlatformViewFactory;
+        content = factoryFunction(viewId) as DomElement;
       }
 
       _ensureContentCorrectlySized(content, viewType);

lib/web_ui/lib/src/engine/platform_views/message_handler.dart

@@ -68,6 +68,7 @@ class PlatformViewMessageHandler {
     final Map<dynamic, dynamic> args = methodCall.arguments as Map<dynamic, dynamic>;
     final int viewId = args.readInt('id');
     final String viewType = args.readString('viewType');
+    final Object? params = args['params'];
 
     if (!_contentManager.knowsViewType(viewType)) {
       callback(_codec.encodeErrorEnvelope(
@@ -89,11 +90,10 @@ class PlatformViewMessageHandler {
       return;
     }
 
-    // TODO(hterkelsen): How can users add extra `args` from the HtmlElementView widget?
     final DomElement content = _contentManager.renderContent(
       viewType,
       viewId,
-      args,
+      params,
     );
 
     // For now, we don't need anything fancier. If needed, this can be converted

lib/web_ui/lib/ui_web/src/ui_web/platform_view_registry.dart

@@ -4,21 +4,32 @@
 
 import 'package:ui/src/engine.dart';
 
+/// A function which takes a unique `id` and some `params` and creates an HTML
+/// element.
+typedef ParameterizedPlatformViewFactory = Object Function(
+  int viewId, {
+  Object? params,
+});
+
+/// A function which takes a unique `id` and creates an HTML element.
+typedef PlatformViewFactory = Object Function(int viewId);
+
 /// The platform view registry for this app.
 final PlatformViewRegistry platformViewRegistry = PlatformViewRegistry();
 
 /// A registry for factories that create platform views.
 class PlatformViewRegistry {
-  /// Register [viewTypeId] as being creating by the given [viewFactory].
-  /// [viewFactory] can be any function that takes an integer and returns an
-  /// `HTMLElement` DOM object.
+  /// Register [viewType] as being created by the given [viewFactory].
+  ///
+  /// [viewFactory] can be any function that takes an integer and optional
+  /// `params` and returns an `HTMLElement` DOM object.
   bool registerViewFactory(
-    String viewTypeId,
-    Object Function(int viewId) viewFactory, {
+    String viewType,
+    Function viewFactory, {
     bool isVisible = true,
   }) {
     return platformViewManager.registerFactory(
-      viewTypeId,
+      viewType,
       viewFactory,
       isVisible: isVisible,
     );

lib/web_ui/test/engine/platform_views/message_handler_test.dart

@@ -15,6 +15,8 @@ void main() {
 
 const MethodCodec codec = StandardMethodCodec();
 
+typedef PlatformViewFactoryCall = ({int viewId, Object? params});
+
 void testMain() {
   group('PlatformViewMessageHandler', () {
     group('handlePlatformViewCall', () {
@@ -109,6 +111,80 @@ void testMain() {
               reason:
                   'The response should be a success envelope, with null in it.');
         });
+
+        test('passes creation params to the factory', () async {
+          final List<PlatformViewFactoryCall> factoryCalls = <PlatformViewFactoryCall>[];
+          contentManager.registerFactory(viewType, (int viewId, {Object? params}) {
+            factoryCalls.add((viewId: viewId, params: params));
+            return createDomHTMLDivElement();
+          });
+          final PlatformViewMessageHandler messageHandler = PlatformViewMessageHandler(
+            contentManager: contentManager,
+          );
+
+          final List<Completer<ByteData?>> completers = <Completer<ByteData?>>[];
+
+          completers.add(Completer<ByteData?>());
+          messageHandler.handlePlatformViewCall(
+            _getCreateMessage(viewType, 111),
+            completers.last.complete,
+          );
+
+          completers.add(Completer<ByteData?>());
+          messageHandler.handlePlatformViewCall(
+            _getCreateMessage(viewType, 222, <dynamic, dynamic>{'foo': 'bar'}),
+            completers.last.complete,
+          );
+
+          completers.add(Completer<ByteData?>());
+          messageHandler.handlePlatformViewCall(
+            _getCreateMessage(viewType, 333, 'foobar'),
+            completers.last.complete,
+          );
+
+          completers.add(Completer<ByteData?>());
+          messageHandler.handlePlatformViewCall(
+            _getCreateMessage(viewType, 444, <dynamic>[1, null, 'str']),
+            completers.last.complete,
+          );
+
+          final List<ByteData?> responses = await Future.wait(
+            completers.map((Completer<ByteData?> c) => c.future),
+          );
+
+          for (final ByteData? response in responses) {
+            expect(
+              codec.decodeEnvelope(response!),
+              isNull,
+              reason: 'The response should be a success envelope, with null in it.',
+            );
+          }
+
+          expect(factoryCalls, hasLength(4));
+          expect(factoryCalls[0].viewId, 111);
+          expect(factoryCalls[0].params, isNull);
+          expect(factoryCalls[1].viewId, 222);
+          expect(factoryCalls[1].params, <dynamic, dynamic>{'foo': 'bar'});
+          expect(factoryCalls[2].viewId, 333);
+          expect(factoryCalls[2].params, 'foobar');
+          expect(factoryCalls[3].viewId, 444);
+          expect(factoryCalls[3].params, <dynamic>[1, null, 'str']);
+        });
+
+        test('fails if the factory returns a non-DOM object', () async {
+          contentManager.registerFactory(viewType, (int viewId) {
+            // Return an object that's not a DOM element.
+            return Object();
+          });
+
+          final PlatformViewMessageHandler messageHandler =
+              PlatformViewMessageHandler(contentManager: contentManager);
+          final ByteData? message = _getCreateMessage(viewType, viewId);
+
+          expect(() {
+            messageHandler.handlePlatformViewCall(message, (_) {});
+          }, throwsA(isA<TypeError>()));
+        });
       });
 
       group('"dispose" message', () {
@@ -162,12 +238,13 @@ class _FakePlatformViewManager extends PlatformViewManager {
   }
 }
 
-ByteData? _getCreateMessage(String viewType, int viewId) {
+ByteData? _getCreateMessage(String viewType, int viewId, [Object? params]) {
   return codec.encodeMethodCall(MethodCall(
     'create',
     <String, dynamic>{
       'id': viewId,
       'viewType': viewType,
+      if (params != null) 'params': params,
     },
   ));
 }