[web] Move text editing nodes outside of shadowDOM

lib/web_ui/lib/src/engine/embedder.dart

@@ -124,6 +124,9 @@ class FlutterViewEmbedder {
   HostNode get glassPaneShadow => _glassPaneShadow;
   late HostNode _glassPaneShadow;
 
+  DomElement get textEditingHostNode => _textEditingHostNode;
+  late DomElement _textEditingHostNode;
+
   static const String defaultFontStyle = 'normal';
   static const String defaultFontWeight = 'normal';
   static const double defaultFontSize = 14;
@@ -168,6 +171,9 @@ class FlutterViewEmbedder {
     );
     _glassPaneShadow = glassPaneElementHostNode;
 
+    _textEditingHostNode =
+        createTextEditingHostNode(glassPaneElement, defaultCssFont);
+
     // Don't allow the scene to receive pointer events.
     _sceneHostElement = domDocument.createElement('flt-scene-host')
       ..style.pointerEvents = 'none';
@@ -189,20 +195,20 @@ class FlutterViewEmbedder {
     glassPaneElementHostNode.appendAll(<DomNode>[
       accessibilityPlaceholder,
       _sceneHostElement!,
-
-      // The semantic host goes last because hit-test order-wise it must be
-      // first. If semantics goes under the scene host, platform views will
-      // obscure semantic elements.
-      //
-      // You may be wondering: wouldn't semantics obscure platform views and
-      // make then not accessible? At least with some careful planning, that
-      // should not be the case. The semantics tree makes all of its non-leaf
-      // elements transparent. This way, if a platform view appears among other
-      // interactive Flutter widgets, as long as those widgets do not intersect
-      // with the platform view, the platform view will be reachable.
-      semanticsHostElement,
     ]);
 
+    // The semantic host goes last because hit-test order-wise it must be
+    // first. If semantics goes under the scene host, platform views will
+    // obscure semantic elements.
+    //
+    // You may be wondering: wouldn't semantics obscure platform views and
+    // make then not accessible? At least with some careful planning, that
+    // should not be the case. The semantics tree makes all of its non-leaf
+    // elements transparent. This way, if a platform view appears among other
+    // interactive Flutter widgets, as long as those widgets do not intersect
+    // with the platform view, the platform view will be reachable.
+    glassPaneElement.appendChild(semanticsHostElement);
+
     // When debugging semantics, make the scene semi-transparent so that the
     // semantics tree is more prominent.
     if (configuration.debugShowSemanticsNodes) {
@@ -393,3 +399,24 @@ FlutterViewEmbedder? _flutterViewEmbedder;
 FlutterViewEmbedder ensureFlutterViewEmbedderInitialized() =>
     _flutterViewEmbedder ??=
         FlutterViewEmbedder(hostElement: configuration.hostElement);
+
+/// Creates a node to host text editing elements and applies a stylesheet
+/// to Flutter nodes that exist outside of the shadowDOM.
+DomElement createTextEditingHostNode(DomElement root, String defaultFont) {
+  final DomElement domElement =
+      domDocument.createElement('flt-text-editing-host');
+  final DomHTMLStyleElement styleElement = createDomHTMLStyleElement();
+
+  styleElement.id = 'flt-text-editing-stylesheet';
+  root.appendChild(styleElement);
+  applyGlobalCssRulesToSheet(
+    styleElement.sheet! as DomCSSStyleSheet,
+    hasAutofillOverlay: browserHasAutofillOverlay(),
+    cssSelectorPrefix: FlutterViewEmbedder.glassPaneTagName,
+    defaultCssFont: defaultFont,
+  );
+
+  root.appendChild(domElement);
+
+  return domElement;
+}

lib/web_ui/lib/src/engine/host_node.dart

@@ -94,6 +94,8 @@ abstract class HostNode {
   /// See:
   /// * [Document.querySelectorAll](https://developer.mozilla.org/en-US/docs/Web/API/Document/querySelectorAll)
   Iterable<DomElement> querySelectorAll(String selectors);
+
+  DomElement get renderHost;
 }
 
 /// A [HostNode] implementation, backed by a [DomShadowRoot].
@@ -110,11 +112,10 @@ class ShadowDomHostNode implements HostNode {
   /// This also calls [applyGlobalCssRulesToSheet], with the [defaultFont]
   /// to be used as the default font definition.
   ShadowDomHostNode(DomElement root, String defaultFont)
-      : assert(
-          root.isConnected ?? true,
-          'The `root` of a ShadowDomHostNode must be connected to the Document object or a ShadowRoot.'
-        ) {
-    _shadow = root.attachShadow(<String, dynamic>{
+      : assert(root.isConnected ?? true,
+            'The `root` of a ShadowDomHostNode must be connected to the Document object or a ShadowRoot.') {
+    root.appendChild(renderHost);
+    _shadow = renderHost.attachShadow(<String, dynamic>{
       'mode': 'open',
       // This needs to stay false to prevent issues like this:
       // - https://github.com/flutter/flutter/issues/85759
@@ -135,6 +136,9 @@ class ShadowDomHostNode implements HostNode {
 
   late DomShadowRoot _shadow;
 
+  @override
+  final DomElement renderHost = domDocument.createElement('flt-render-host');
+
   @override
   DomElement? get activeElement => _shadow.activeElement;
 
@@ -191,6 +195,9 @@ class ElementHostNode implements HostNode {
 
   late DomElement _element;
 
+  @override
+  final DomElement renderHost = domDocument.createElement('flt-render-host');
+
   @override
   DomElement? get activeElement => _element.ownerDocument?.activeElement;
 

lib/web_ui/lib/src/engine/platform_dispatcher.dart

@@ -589,7 +589,7 @@ class EnginePlatformDispatcher extends ui.PlatformDispatcher {
         _platformViewMessageHandler ??= PlatformViewMessageHandler(
           contentManager: platformViewManager,
           contentHandler: (DomElement content) {
-            flutterViewEmbedder.glassPaneElement.append(content);
+            flutterViewEmbedder.glassPaneShadow.renderHost.append(content);
           },
         );
         _platformViewMessageHandler!.handlePlatformViewCall(data, callback!);

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

@@ -128,8 +128,9 @@ class PlatformViewManager {
       }
 
       _ensureContentCorrectlySized(content, viewType);
+      wrapper.append(content);
 
-      return wrapper..append(content);
+      return wrapper;
     });
   }
 

lib/web_ui/lib/src/engine/pointer_binding/event_position_helper.dart

@@ -19,14 +19,14 @@ import '../semantics.dart' show EngineSemanticsOwner;
 /// It also takes into account semantics being enabled to fix the case where
 /// offsetX, offsetY == 0 (TalkBack events).
 ui.Offset computeEventOffsetToTarget(DomMouseEvent event, DomElement actualTarget) {
-  // On top of a platform view
-  if (event.target != actualTarget) {
-    return _computeOffsetOnPlatformView(event, actualTarget);
-  }
   // On a TalkBack event
   if (EngineSemanticsOwner.instance.semanticsEnabled && event.offsetX == 0 && event.offsetY == 0) {
     return _computeOffsetForTalkbackEvent(event, actualTarget);
   }
+  // On top of a platform view
+  if (event.target != actualTarget) {
+    return _computeOffsetOnPlatformView(event, actualTarget);
+  }
   // Return the offsetX/Y in the normal case.
   // (This works with 3D translations of the parent element.)
   return ui.Offset(event.offsetX, event.offsetY);

lib/web_ui/lib/src/engine/semantics/text_field.dart

@@ -7,7 +7,6 @@ import 'package:ui/ui.dart' as ui;
 
 import '../browser_detection.dart';
 import '../dom.dart';
-import '../embedder.dart';
 import '../platform_dispatcher.dart';
 import '../safe_browser_api.dart';
 import '../text_editing/text_editing.dart';
@@ -424,14 +423,14 @@ class TextField extends RoleManager {
         ..height = '${semanticsObject.rect!.height}px';
 
       if (semanticsObject.hasFocus) {
-        if (flutterViewEmbedder.glassPaneShadow.activeElement !=
+        if (domDocument.activeElement !=
             activeEditableElement) {
           semanticsObject.owner.addOneTimePostUpdateCallback(() {
             activeEditableElement.focus();
           });
         }
         SemanticsTextEditingStrategy._instance?.activate(this);
-      } else if (flutterViewEmbedder.glassPaneShadow.activeElement ==
+      } else if (domDocument.activeElement ==
           activeEditableElement) {
         if (!isIosSafari) {
           SemanticsTextEditingStrategy._instance?.deactivate(this);

lib/web_ui/lib/src/engine/text_editing/text_editing.dart

@@ -51,7 +51,8 @@ void _emptyCallback(dynamic _) {}
 
 /// The default [HostNode] that hosts all DOM required for text editing when a11y is not enabled.
 @visibleForTesting
-HostNode get defaultTextEditingRoot => flutterViewEmbedder.glassPaneShadow;
+DomElement get defaultTextEditingRoot =>
+    flutterViewEmbedder.textEditingHostNode;
 
 /// These style attributes are constant throughout the life time of an input
 /// element.

lib/web_ui/test/engine/host_node_test.dart

@@ -16,19 +16,20 @@ void testMain() {
 
   group('ShadowDomHostNode', () {
     final HostNode hostNode = ShadowDomHostNode(rootNode, '14px monospace');
+    final DomElement renderHost = domDocument.querySelector('flt-render-host')!;
 
     test('Initializes and attaches a shadow root', () {
       expect(domInstanceOfString(hostNode.node, 'ShadowRoot'), isTrue);
-      expect((hostNode.node as DomShadowRoot).host, rootNode);
-      expect(hostNode.node, rootNode.shadowRoot);
+      expect((hostNode.node as DomShadowRoot).host, renderHost);
+      expect(hostNode.node, renderHost.shadowRoot);
 
       // The shadow root should be initialized with correct parameters.
-      expect(rootNode.shadowRoot!.mode, 'open');
+      expect(renderHost.shadowRoot!.mode, 'open');
       if (browserEngine != BrowserEngine.firefox &&
           browserEngine != BrowserEngine.webkit) {
         // Older versions of Safari and Firefox don't support this flag yet.
         // See: https://caniuse.com/mdn-api_shadowroot_delegatesfocus
-        expect(rootNode.shadowRoot!.delegatesFocus, isFalse);
+        expect(renderHost.shadowRoot!.delegatesFocus, isFalse);
       }
     });