[flutter] prevent errant text field clicks from losing focus (#86041)

packages/flutter/lib/src/material/text_field.dart

@@ -1306,7 +1306,9 @@ class _TextFieldState extends State<TextField> with RestorationMixin implements
       semanticsMaxValueLength = null;
     }
 
-    return MouseRegion(
+    return FocusTrapArea(
+      focusNode: focusNode,
+      child: MouseRegion(
         cursor: effectiveMouseCursor,
         onEnter: (PointerEnterEvent event) => _handleHover(true),
         onExit: (PointerExitEvent event) => _handleHover(false),
@@ -1333,6 +1335,7 @@ class _TextFieldState extends State<TextField> with RestorationMixin implements
             ),
           ),
         ),
+      ),
     );
   }
 }

packages/flutter/lib/src/widgets/editable_text.dart

@@ -1654,13 +1654,12 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
       widget.focusNode.addListener(_handleFocusChanged);
       updateKeepAlive();
     }
+
     if (!_shouldCreateInputConnection) {
       _closeInputConnectionIfNeeded();
-    } else {
-      if (oldWidget.readOnly && _hasFocus) {
+    } else if (oldWidget.readOnly && _hasFocus) {
       _openInputConnection();
     }
-    }
 
     if (kIsWeb && _hasInputConnection) {
       if (oldWidget.readOnly != widget.readOnly) {

packages/flutter/lib/src/widgets/routes.dart

@@ -814,7 +814,7 @@ class _ModalScopeState<T> extends State<_ModalScope<T>> {
                     controller: primaryScrollController,
                     child: FocusScope(
                       node: focusScopeNode, // immutable
-                      child: _FocusTrap(
+                      child: FocusTrap(
                         focusScopeNode: focusScopeNode,
                         child: RepaintBoundary(
                           child: AnimatedBuilder(
@@ -1987,16 +1987,32 @@ typedef RoutePageBuilder = Widget Function(BuildContext context, Animation<doubl
 /// See [ModalRoute.buildTransitions] for complete definition of the parameters.
 typedef RouteTransitionsBuilder = Widget Function(BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation, Widget child);
 
+/// The [FocusTrap] widget removes focus when a mouse primary pointer makes contact with another
+/// region of the screen.
+///
 /// When a primary pointer makes contact with the screen, this widget determines if that pointer
 /// contacted an existing focused widget. If not, this asks the [FocusScopeNode] to reset the
 /// focus state. This allows [TextField]s and other focusable widgets to give up their focus
 /// state, without creating a gesture detector that competes with others on screen.
-class _FocusTrap extends SingleChildRenderObjectWidget {
-  const _FocusTrap({
+///
+/// In cases where focus is conceptually larger than the focused render object, a [FocusTrapArea]
+/// can be used to expand the focus area to include all render objects below that. This is used by
+/// the [TextField] widgets to prevent a loss of focus when interacting with decorations on the
+/// text area.
+///
+/// See also:
+///
+///  * [FocusTrapArea], the widget that allows expanding the conceptual focus area.
+class FocusTrap extends SingleChildRenderObjectWidget {
+
+  /// Create a new [FocusTrap] widget scoped to the provided [focusScopeNode].
+  const FocusTrap({
     required this.focusScopeNode,
     required Widget child,
-  }) : super(child: child);
+    Key? key,
+  }) : super(child: child, key: key);
 
+  /// The [focusScopeNode] that this focus trap widget operates on.
   final FocusScopeNode focusScopeNode;
 
   @override
@@ -2005,11 +2021,50 @@ class _FocusTrap extends SingleChildRenderObjectWidget {
   }
 
   @override
-  void updateRenderObject(BuildContext context, covariant _RenderFocusTrap renderObject) {
+  void updateRenderObject(BuildContext context, RenderObject renderObject) {
+    if (renderObject is _RenderFocusTrap)
       renderObject.focusScopeNode = focusScopeNode;
   }
 }
 
+/// Declares a widget subtree which is part of the provided [focusNode]'s focus area
+/// without attaching focus to that region.
+///
+/// This is used by text field widgets which decorate a smaller editable text area.
+/// This area is conceptually part of the editable text, but not attached to the
+/// focus context. The [FocusTrapArea] is used to inform the framework of this
+/// relationship, so that primary pointer contact inside of this region but above
+/// the editable text focus will not trigger loss of focus.
+///
+/// See also:
+///
+///  * [FocusTrap], the widget which removes focus based on primary pointer interactions.
+class FocusTrapArea extends SingleChildRenderObjectWidget {
+
+  /// Create a new [FocusTrapArea] that expands the area of the provided [focusNode].
+  const FocusTrapArea({required this.focusNode, Key? key, Widget? child}) : super(key: key, child: child);
+
+  /// The [FocusNode] that the focus trap area will expand to.
+  final FocusNode focusNode;
+
+  @override
+  RenderObject createRenderObject(BuildContext context) {
+    return _RenderFocusTrapArea(focusNode);
+  }
+
+  @override
+  void updateRenderObject(BuildContext context, RenderObject renderObject) {
+    if (renderObject is _RenderFocusTrapArea)
+      renderObject.focusNode = focusNode;
+  }
+}
+
+class _RenderFocusTrapArea extends RenderProxyBox {
+  _RenderFocusTrapArea(this.focusNode);
+
+  FocusNode focusNode;
+}
+
 class _RenderFocusTrap extends RenderProxyBoxWithHitTestBehavior {
   _RenderFocusTrap(this._focusScopeNode);
 
@@ -2079,6 +2134,10 @@ class _RenderFocusTrap extends RenderProxyBoxWithHitTestBehavior {
         hitCurrentFocus = true;
         break;
       }
+      if (target is _RenderFocusTrapArea && target.focusNode == focusNode) {
+        hitCurrentFocus = true;
+        break;
+      }
     }
     if (!hitCurrentFocus)
       focusNode.unfocus(disposition: UnfocusDisposition.scope);

packages/flutter/test/material/debug_test.dart

@@ -134,7 +134,7 @@ void main() {
       '     _FadeUpwardsPageTransition\n'
       '     AnimatedBuilder\n'
       '     RepaintBoundary\n'
-      '     _FocusTrap\n'
+      '     FocusTrap\n'
       '     _FocusMarker\n'
       '     Semantics\n'
       '     FocusScope\n'

packages/flutter/test/material/text_field_focus_test.dart

@@ -431,6 +431,45 @@ void main() {
     expect(focusNodeB.hasFocus, true);
   }, variant: TargetPlatformVariant.desktop());
 
+  testWidgets('A Focused text-field will not lose focus when clicking on its decoration', (WidgetTester tester) async {
+    final FocusNode focusNodeA = FocusNode();
+    final Key iconKey = UniqueKey();
+
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Material(
+          child: ListView(
+            children: <Widget>[
+              TextField(
+                focusNode: focusNodeA,
+                decoration: InputDecoration(
+                  icon: Icon(Icons.copy_all, key: iconKey),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+
+    final TestGesture down1 = await tester.startGesture(tester.getCenter(find.byType(TextField).first), kind: PointerDeviceKind.mouse);
+    await tester.pump();
+    await tester.pumpAndSettle();
+    await down1.up();
+    await down1.removePointer();
+
+    expect(focusNodeA.hasFocus, true);
+
+    // Click on the icon which has a different RO than the text field's focus node context
+    final TestGesture down2 = await tester.startGesture(tester.getCenter(find.byKey(iconKey)), kind: PointerDeviceKind.mouse);
+    await tester.pump();
+    await tester.pumpAndSettle();
+    await down2.up();
+    await down2.removePointer();
+
+    expect(focusNodeA.hasFocus, true);
+  }, variant: TargetPlatformVariant.desktop());
+
   testWidgets('A Focused text-field will lose focus when clicking outside of its hitbox with a mouse on desktop after tab navigation', (WidgetTester tester) async {
     final FocusNode focusNodeA = FocusNode();
     final FocusNode focusNodeB = FocusNode();

packages/flutter_test/test/widget_tester_live_device_test.dart

@@ -52,9 +52,9 @@ Some possible finders for the widgets at Offset(400.0, 300.0):
   find.byType(FadeTransition)
   find.byType(FractionalTranslation)
   find.byType(SlideTransition)
+  find.widgetWithText(FocusTrap, 'Test')
   find.widgetWithText(PrimaryScrollController, 'Test')
   find.widgetWithText(PageStorage, 'Test')
-  find.widgetWithText(Offstage, 'Test')
 '''.trim().split('\n')));
     printedMessages.clear();