Wire up SemanticsAction.focus to the framework (#149374)

Wire up `SemanticsAction.focus` to `Semantics` and `CustomPaint`. Reenable respective tests, and add `focus` tests to them.

Contributes to a fix for flutter/flutter#83809

Author: yjbanov

packages/flutter/lib/src/rendering/custom_paint.dart

@@ -1036,6 +1036,9 @@ class RenderCustomPaint extends RenderProxyBox {
     if (properties.onDidLoseAccessibilityFocus != null) {
       config.onDidLoseAccessibilityFocus = properties.onDidLoseAccessibilityFocus;
     }
+    if (properties.onFocus != null) {
+      config.onFocus = properties.onFocus;
+    }
     if (properties.onDismiss != null) {
       config.onDismiss = properties.onDismiss;
     }

packages/flutter/lib/src/rendering/proxy_box.dart

@@ -4467,6 +4467,9 @@ class RenderSemanticsAnnotations extends RenderProxyBox {
     if (_properties.onDidLoseAccessibilityFocus != null) {
       config.onDidLoseAccessibilityFocus = _performDidLoseAccessibilityFocus;
     }
+    if (_properties.onFocus != null) {
+      config.onFocus = _performFocus;
+    }
     if (_properties.customSemanticsActions != null) {
       config.customSemanticsActions = _properties.customSemanticsActions!;
     }
@@ -4551,6 +4554,10 @@ class RenderSemanticsAnnotations extends RenderProxyBox {
   void _performDidLoseAccessibilityFocus() {
     _properties.onDidLoseAccessibilityFocus?.call();
   }
+
+  void _performFocus() {
+    _properties.onFocus?.call();
+  }
 }
 
 /// Causes the semantics of all earlier render objects below the same semantic

packages/flutter/lib/src/semantics/semantics.dart

@@ -943,6 +943,7 @@ class SemanticsProperties extends DiagnosticableTree {
     this.onSetText,
     this.onDidGainAccessibilityFocus,
     this.onDidLoseAccessibilityFocus,
+    this.onFocus,
     this.onDismiss,
     this.customSemanticsActions,
   }) : assert(label == null || attributedLabel == null, 'Only one of label or attributedLabel should be provided'),
@@ -1605,6 +1606,8 @@ class SemanticsProperties extends DiagnosticableTree {
   ///
   ///  * [onDidLoseAccessibilityFocus], which is invoked when the accessibility
   ///    focus is removed from the node.
+  ///  * [onFocus], which is invoked when the assistive technology requests that
+  ///    the input focus is gained by a widget.
   ///  * [FocusNode], [FocusScope], [FocusManager], which manage the input focus.
   final VoidCallback? onDidGainAccessibilityFocus;
 
@@ -1627,6 +1630,30 @@ class SemanticsProperties extends DiagnosticableTree {
   ///  * [FocusNode], [FocusScope], [FocusManager], which manage the input focus.
   final VoidCallback? onDidLoseAccessibilityFocus;
 
+  /// {@template flutter.semantics.SemanticsProperties.onFocus}
+  /// The handler for [SemanticsAction.focus].
+  ///
+  /// This handler is invoked when the assistive technology requests that the
+  /// focusable widget corresponding to this semantics node gain input focus.
+  /// The [FocusNode] that manages the focus of the widget must gain focus. The
+  /// widget must begin responding to relevant key events. For example:
+  ///
+  /// * Buttons must respond to tap/click events produced via keyboard shortcuts.
+  /// * Text fields must become focused and editable, showing an on-screen
+  ///   keyboard, if necessary.
+  /// * Checkboxes, switches, and radio buttons must become togglable using
+  ///   keyboard shortcuts.
+  ///
+  /// Focus behavior is specific to the platform and to the assistive technology
+  /// used. See the documentation of [SemanticsAction.focus] for more detail.
+  ///
+  /// See also:
+  ///
+  ///  * [onDidGainAccessibilityFocus], which is invoked when the node gains
+  ///    accessibility focus.
+  /// {@endtemplate}
+  final VoidCallback? onFocus;
+
   /// The handler for [SemanticsAction.dismiss].
   ///
   /// This is a request to dismiss the currently focused node.
@@ -4064,6 +4091,14 @@ class SemanticsConfiguration {
     _onDidLoseAccessibilityFocus = value;
   }
 
+  /// {@macro flutter.semantics.SemanticsProperties.onFocus}
+  VoidCallback? get onFocus => _onFocus;
+  VoidCallback? _onFocus;
+  set onFocus(VoidCallback? value) {
+    _addArgumentlessAction(SemanticsAction.focus, value!);
+    _onFocus = value;
+  }
+
   /// A delegate that decides how to handle [SemanticsConfiguration]s produced
   /// in the widget subtree.
   ///

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

@@ -7151,6 +7151,7 @@ class Semantics extends SingleChildRenderObjectWidget {
     SetTextHandler? onSetText,
     VoidCallback? onDidGainAccessibilityFocus,
     VoidCallback? onDidLoseAccessibilityFocus,
+    VoidCallback? onFocus,
     Map<CustomSemanticsAction, VoidCallback>? customSemanticsActions,
   }) : this.fromProperties(
     key: key,
@@ -7215,6 +7216,7 @@ class Semantics extends SingleChildRenderObjectWidget {
       onMoveCursorBackwardByCharacter: onMoveCursorBackwardByCharacter,
       onDidGainAccessibilityFocus: onDidGainAccessibilityFocus,
       onDidLoseAccessibilityFocus: onDidLoseAccessibilityFocus,
+      onFocus: onFocus,
       onDismiss: onDismiss,
       onSetSelection: onSetSelection,
       onSetText: onSetText,

packages/flutter/test/widgets/custom_painter_test.dart

@@ -342,6 +342,7 @@ void _defineTests() {
             onSetText: (String text) => performedActions.add(SemanticsAction.setText),
             onDidGainAccessibilityFocus: () => performedActions.add(SemanticsAction.didGainAccessibilityFocus),
             onDidLoseAccessibilityFocus: () => performedActions.add(SemanticsAction.didLoseAccessibilityFocus),
+            onFocus: () => performedActions.add(SemanticsAction.focus),
           ),
         ),
       ),
@@ -400,19 +401,16 @@ void _defineTests() {
         case SemanticsAction.scrollUp:
         case SemanticsAction.showOnScreen:
         case SemanticsAction.tap:
+        case SemanticsAction.focus:
           semanticsOwner.performAction(expectedId, action);
-        // TODO(yjbanov): temporary adding default case until https://github.com/flutter/engine/pull/53094 rolls in (see https://github.com/flutter/flutter/issues/83809)
-        // ignore: no_default_cases
-        default:
-          throw UnimplementedError();
       }
       expect(performedActions.length, expectedLength);
       expect(performedActions.last, action);
       expectedLength += 1;
     }
 
     semantics.dispose();
-  }, skip: true); // TODO(yjbanov): temporary skip until https://github.com/flutter/engine/pull/53094 rolls in (see https://github.com/flutter/flutter/issues/83809)
+  });
 
   testWidgets('Supports all flags', (WidgetTester tester) async {
     final SemanticsTester semantics = SemanticsTester(tester);

packages/flutter/test/widgets/semantics_test.dart

@@ -516,6 +516,7 @@ void main() {
         onSetText: (String _) => performedActions.add(SemanticsAction.setText),
         onDidGainAccessibilityFocus: () => performedActions.add(SemanticsAction.didGainAccessibilityFocus),
         onDidLoseAccessibilityFocus: () => performedActions.add(SemanticsAction.didLoseAccessibilityFocus),
+        onFocus: () => performedActions.add(SemanticsAction.focus),
       ),
     );
 
@@ -570,19 +571,16 @@ void main() {
         case SemanticsAction.scrollUp:
         case SemanticsAction.showOnScreen:
         case SemanticsAction.tap:
+        case SemanticsAction.focus:
           semanticsOwner.performAction(expectedId, action);
-        // TODO(yjbanov): temporary adding default case until https://github.com/flutter/engine/pull/53094 rolls in (see https://github.com/flutter/flutter/issues/83809)
-        // ignore: no_default_cases
-        default:
-          throw UnimplementedError();
       }
       expect(performedActions.length, expectedLength);
       expect(performedActions.last, action);
       expectedLength += 1;
     }
 
     semantics.dispose();
-  }, skip: true); // TODO(yjbanov): temporary skip until https://github.com/flutter/engine/pull/53094 rolls in (see https://github.com/flutter/flutter/issues/83809)
+  });
 
   testWidgets('Semantics widget supports all flags', (WidgetTester tester) async {
     final SemanticsTester semantics = SemanticsTester(tester);