fix: ensure hardware pointer events do not reach underlying webview

This fixes the issue on iOS and Android (including Chromebook) where hardware mouse events were being captured by an underlying webview.

packages/pointer_interceptor/lib/src/mobile.dart

@@ -2,7 +2,10 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:io';
+
 import 'package:flutter/widgets.dart';
+import 'package:webview_flutter/webview_flutter.dart';
 
 /// A [Widget] that prevents clicks from being swallowed by [HtmlElementView]s.
 class PointerInterceptor extends StatelessWidget {
@@ -29,6 +32,16 @@ class PointerInterceptor extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    return child;
+    if (Platform.isAndroid || Platform.isIOS) {
+      return Stack(alignment: Alignment.center, children: <Widget>[
+        Opacity(
+          opacity: 0,
+          child: WebViewWidget(controller: WebViewController()),
+        ),
+        child,
+      ]);
+    } else {
+      return child;
+    }
   }
 }

packages/pointer_interceptor/pubspec.yaml

@@ -11,6 +11,7 @@ environment:
 dependencies:
   flutter:
     sdk: flutter
+  webview_flutter: ^4.0.7
 
 dev_dependencies:
   flutter_test: