fix(web): prevent browser context menu over task menus (#1627)

ui/flutter/lib/shared/widgets/browser_context_menu_region.dart

@@ -0,0 +1,81 @@
+import 'package:flutter/foundation.dart';
+import 'package:flutter/rendering.dart';
+import 'package:flutter/widgets.dart';
+
+import 'browser_context_menu_region_stub.dart'
+    if (dart.library.js_interop) 'browser_context_menu_region_web.dart'
+    as platform;
+
+/// Keeps the browser menu out of an application's context-menu region on Web.
+///
+/// Captured themes carry the policy into shadcn's menu and submenu overlays.
+/// Overlay regions defer to their children so a full-screen positioning layer
+/// does not suppress the browser menu over the rest of the page.
+class BrowserContextMenuRegion extends StatelessWidget {
+  const BrowserContextMenuRegion({super.key, required this.child});
+
+  final Widget child;
+
+  @override
+  Widget build(BuildContext context) {
+    if (!kIsWeb) return child;
+    return _ContextMenuTheme(
+      child: _ContextMenuRegion(behavior: HitTestBehavior.translucent, child: child),
+    );
+  }
+}
+
+class _ContextMenuTheme extends InheritedTheme {
+  const _ContextMenuTheme({required super.child});
+
+  @override
+  Widget wrap(BuildContext context, Widget child) {
+    return _ContextMenuTheme(child: _ContextMenuRegion(child: child));
+  }
+
+  @override
+  bool updateShouldNotify(_ContextMenuTheme oldWidget) => false;
+}
+
+class _ContextMenuRegion extends SingleChildRenderObjectWidget {
+  const _ContextMenuRegion({this.behavior = HitTestBehavior.deferToChild, required super.child});
+
+  final HitTestBehavior behavior;
+
+  @override
+  RenderObject createRenderObject(BuildContext context) {
+    return _RenderContextMenuRegion(View.of(context).viewId, behavior);
+  }
+
+  @override
+  void updateRenderObject(BuildContext context, _RenderContextMenuRegion renderObject) {
+    renderObject
+      ..viewId = View.of(context).viewId
+      ..behavior = behavior;
+  }
+}
+
+class _RenderContextMenuRegion extends RenderProxyBoxWithHitTestBehavior {
+  _RenderContextMenuRegion(this._viewId, HitTestBehavior behavior) : super(behavior: behavior);
+
+  int _viewId;
+
+  set viewId(int value) {
+    if (value == _viewId) return;
+    if (attached) platform.unregisterRegion(this, _viewId);
+    _viewId = value;
+    if (attached) platform.registerRegion(this, _viewId);
+  }
+
+  @override
+  void attach(PipelineOwner owner) {
+    super.attach(owner);
+    platform.registerRegion(this, _viewId);
+  }
+
+  @override
+  void detach() {
+    platform.unregisterRegion(this, _viewId);
+    super.detach();
+  }
+}

ui/flutter/lib/shared/widgets/browser_context_menu_region_stub.dart

@@ -0,0 +1,5 @@
+import 'package:flutter/rendering.dart';
+
+void registerRegion(RenderBox region, int viewId) {}
+
+void unregisterRegion(RenderBox region, int viewId) {}

ui/flutter/lib/shared/widgets/browser_context_menu_region_web.dart

@@ -0,0 +1,51 @@
+import 'dart:js_interop';
+import 'dart:ui' as ui;
+import 'dart:ui_web' as ui_web;
+
+import 'package:flutter/rendering.dart';
+import 'package:web/web.dart' as web;
+
+final _regions = <int, Set<RenderBox>>{};
+JSFunction? _listener;
+
+void registerRegion(RenderBox region, int viewId) {
+  _regions.putIfAbsent(viewId, () => <RenderBox>{}).add(region);
+  if (_listener != null) return;
+  _listener = _onContextMenu.toJS;
+  web.document.addEventListener('contextmenu', _listener, true.toJS);
+}
+
+void unregisterRegion(RenderBox region, int viewId) {
+  final regions = _regions[viewId];
+  regions?.remove(region);
+  if (regions?.isEmpty ?? false) _regions.remove(viewId);
+  if (_regions.isNotEmpty) return;
+  web.document.removeEventListener('contextmenu', _listener, true.toJS);
+  _listener = null;
+}
+
+void _onContextMenu(web.MouseEvent event) {
+  if (!event.cancelable || event.defaultPrevented) return;
+  for (final view in ui.PlatformDispatcher.instance.views) {
+    final regions = _regions[view.viewId];
+    if (regions == null) continue;
+    final host = ui_web.views.getHostElement(view.viewId) as web.HTMLElement?;
+    if (host == null || !event.composedPath().toDart.contains(host)) continue;
+    final bounds = host.getBoundingClientRect();
+    if (bounds.width <= 0 || bounds.height <= 0) continue;
+    final x = event.clientX - bounds.left;
+    final y = event.clientY - bounds.top;
+    if (x < 0 || y < 0 || x >= bounds.width || y >= bounds.height) continue;
+
+    // DOM client coordinates are CSS pixels. Map them through the public view
+    // host bounds rather than assuming a DPR, page origin or browser zoom.
+    final logicalSize = view.physicalSize / view.devicePixelRatio;
+    final position = Offset(x * logicalSize.width / bounds.width, y * logicalSize.height / bounds.height);
+    final result = HitTestResult();
+    RendererBinding.instance.hitTestInView(result, position, view.viewId);
+    if (result.path.any((entry) => regions.contains(entry.target))) {
+      event.preventDefault();
+      return;
+    }
+  }
+}