Wire up SemanticsFlag.isHidden (#16772)

bin/internal/engine.version

-09d05a38912a3c1a906e95099cac9a7e14fae85f
+232060828a1d4a9c3ee16b92f3af5f5a15041e32

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

@@ -834,6 +834,9 @@ class RenderCustomPaint extends RenderProxyBox {
     if (properties.obscured != null) {
       config.isObscured = properties.obscured;
     }
+    if (properties.hidden != null) {
+      config.isHidden = properties.hidden;
+    }
     if (properties.header != null) {
       config.isHeader = properties.header;
     }

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

@@ -3021,6 +3021,7 @@ class RenderSemanticsAnnotations extends RenderProxyBox {
     bool obscured,
     bool scopesRoute,
     bool namesRoute,
+    bool hidden,
     String label,
     String value,
     String increasedValue,
@@ -3058,6 +3059,7 @@ class RenderSemanticsAnnotations extends RenderProxyBox {
        _obscured = obscured,
        _scopesRoute = scopesRoute,
        _namesRoute = namesRoute,
+       _hidden = hidden,
        _label = label,
        _value = value,
        _increasedValue = increasedValue,
@@ -3237,6 +3239,17 @@ class RenderSemanticsAnnotations extends RenderProxyBox {
     markNeedsSemanticsUpdate();
   }
 
+  /// If non-null, sets the [SemanticsNode.isHidden] semantic to the given
+  /// value.
+  bool get hidden => _hidden;
+  bool _hidden;
+  set hidden(bool value) {
+    if (hidden == value)
+      return;
+    _hidden = value;
+    markNeedsSemanticsUpdate();
+  }
+
   /// If non-null, sets the [SemanticsNode.label] semantic to the given value.
   ///
   /// The reading direction is given by [textDirection].
@@ -3678,6 +3691,8 @@ class RenderSemanticsAnnotations extends RenderProxyBox {
       config.isInMutuallyExclusiveGroup = inMutuallyExclusiveGroup;
     if (obscured != null)
       config.isObscured = obscured;
+    if (hidden != null)
+      config.isHidden = hidden;
     if (label != null)
       config.label = label;
     if (value != null)

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

@@ -319,6 +319,7 @@ class SemanticsProperties extends DiagnosticableTree {
     this.textField,
     this.focused,
     this.inMutuallyExclusiveGroup,
+    this.hidden,
     this.obscured,
     this.scopesRoute,
     this.namesRoute,
@@ -401,7 +402,25 @@ class SemanticsProperties extends DiagnosticableTree {
   /// For example, a radio button is in a mutually exclusive group because only
   /// one radio button in that group can be marked as [checked].
   final bool inMutuallyExclusiveGroup;
-  
+
+  /// If non-null, whether the node is considered hidden.
+  ///
+  /// Hidden elements are currently not visible on screen. They may be covered
+  /// by other elements or positioned outside of the visible area of a viewport.
+  ///
+  /// Hidden elements cannot gain accessibility focus though regular touch. The
+  /// only way they can be focused is by moving the focus to them via linear
+  /// navigation.
+  ///
+  /// Platforms are free to completely ignore hidden elements and new platforms
+  /// are encouraged to do so.
+  ///
+  /// Instead of marking an element as hidden it should usually be excluded from
+  /// the semantics tree altogether. Hidden elements are only included in the
+  /// semantics tree to work around platform limitations and they are mainly
+  /// used to implement accessibility scrolling on iOS.
+  final bool hidden;
+
   /// If non-null, whether [value] should be obscured.
   ///
   /// This option is usually set in combination with [textField] to indicate
@@ -1442,6 +1461,7 @@ class SemanticsNode extends AbstractNode with DiagnosticableTreeMixin {
     final List<String> flags = SemanticsFlag.values.values.where((SemanticsFlag flag) => _hasFlag(flag)).map((SemanticsFlag flag) => flag.toString().substring('SemanticsFlag.'.length)).toList();
     properties.add(new IterableProperty<String>('flags', flags, ifEmpty: null));
     properties.add(new FlagProperty('isInvisible', value: isInvisible, ifTrue: 'invisible'));
+    properties.add(new FlagProperty('isHidden', value: _hasFlag(SemanticsFlag.isHidden), ifTrue: 'HIDDEN'));
     properties.add(new StringProperty('label', _label, defaultValue: ''));
     properties.add(new StringProperty('value', _value, defaultValue: ''));
     properties.add(new StringProperty('increasedValue', _increasedValue, defaultValue: ''));
@@ -2450,6 +2470,27 @@ class SemanticsConfiguration {
     _setFlag(SemanticsFlag.isHeader, value);
   }
 
+  /// Whether the owning [RenderObject] is considered hidden.
+  ///
+  /// Hidden elements are currently not visible on screen. They may be covered
+  /// by other elements or positioned outside of the visible area of a viewport.
+  ///
+  /// Hidden elements cannot gain accessibility focus though regular touch. The
+  /// only way they can be focused is by moving the focus to them via linear
+  /// navigation.
+  ///
+  /// Platforms are free to completely ignore hidden elements and new platforms
+  /// are encouraged to do so.
+  ///
+  /// Instead of marking an element as hidden it should usually be excluded from
+  /// the semantics tree altogether. Hidden elements are only included in the
+  /// semantics tree to work around platform limitations and they are mainly
+  /// used to implement accessibility scrolling on iOS.
+  bool get isHidden => _hasFlag(SemanticsFlag.isHidden);
+  set isHidden(bool value) {
+    _setFlag(SemanticsFlag.isHidden, value);
+  }
+
   /// Whether the owning [RenderObject] is a text field.
   bool get isTextField => _hasFlag(SemanticsFlag.isTextField);
   set isTextField(bool value) {

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

@@ -4898,6 +4898,7 @@ class Semantics extends SingleChildRenderObjectWidget {
     bool obscured,
     bool scopesRoute,
     bool namesRoute,
+    bool hidden,
     String label,
     String value,
     String increasedValue,
@@ -4938,6 +4939,7 @@ class Semantics extends SingleChildRenderObjectWidget {
       obscured: obscured,
       scopesRoute: scopesRoute,
       namesRoute: namesRoute,
+      hidden: hidden,
       label: label,
       value: value,
       increasedValue: increasedValue,
@@ -5023,6 +5025,7 @@ class Semantics extends SingleChildRenderObjectWidget {
       obscured: properties.obscured,
       scopesRoute: properties.scopesRoute,
       namesRoute: properties.namesRoute,
+      hidden: properties.hidden,
       label: properties.label,
       value: properties.value,
       increasedValue: properties.increasedValue,
@@ -5065,16 +5068,23 @@ class Semantics extends SingleChildRenderObjectWidget {
   void updateRenderObject(BuildContext context, RenderSemanticsAnnotations renderObject) {
     renderObject
       ..container = container
+      ..scopesRoute = properties.scopesRoute
       ..explicitChildNodes = explicitChildNodes
       ..enabled = properties.enabled
       ..checked = properties.checked
       ..selected = properties.selected
+      ..button = properties.button
+      ..header = properties.header
+      ..textField = properties.textField
+      ..focused = properties.focused
+      ..inMutuallyExclusiveGroup = properties.inMutuallyExclusiveGroup
+      ..obscured = properties.obscured
+      ..hidden = properties.hidden
       ..label = properties.label
       ..value = properties.value
       ..increasedValue = properties.increasedValue
       ..decreasedValue = properties.decreasedValue
       ..hint = properties.hint
-      ..scopesRoute = properties.scopesRoute
       ..namesRoute = properties.namesRoute
       ..textDirection = _getTextDirection(context)
       ..sortKey = properties.sortKey

packages/flutter/test/semantics/semantics_test.dart

@@ -361,6 +361,7 @@ void main() {
       '   actions: []\n'
       '   flags: []\n'
       '   invisible\n'
+      '   isHidden: false\n'
       '   label: ""\n'
       '   value: ""\n'
       '   increasedValue: ""\n'

packages/flutter/test/widgets/custom_painter_test.dart

@@ -410,6 +410,7 @@ void _defineTests() {
             enabled: true,
             checked: true,
             selected: true,
+            hidden: true,
             button: true,
             textField: true,
             focused: true,

packages/flutter/test/widgets/semantics_test.dart

@@ -461,8 +461,10 @@ void main() {
     await tester.pumpWidget(
         new Semantics(
           container: true,
+          explicitChildNodes: true,
           // flags
           enabled: true,
+          hidden: true,
           checked: true,
           selected: true,
           button: true,
@@ -473,11 +475,10 @@ void main() {
           obscured: true,
           scopesRoute: true,
           namesRoute: true,
-          explicitChildNodes: true,
         )
     );
 
-    final TestSemantics expectedSemantics = new TestSemantics.root(
+    TestSemantics expectedSemantics = new TestSemantics.root(
       children: <TestSemantics>[
         new TestSemantics.rootChild(
           rect: TestSemantics.fullScreen,
@@ -487,6 +488,19 @@ void main() {
     );
     expect(semantics, hasSemantics(expectedSemantics, ignoreId: true));
 
+    await tester.pumpWidget(new Semantics(
+      container: true,
+    ));
+    expectedSemantics = new TestSemantics.root(
+      children: <TestSemantics>[
+        new TestSemantics.rootChild(
+          rect: TestSemantics.fullScreen,
+          flags: <SemanticsFlag>[],
+        ),
+      ],
+    );
+    expect(semantics, hasSemantics(expectedSemantics, ignoreId: true));
+
     semantics.dispose();
   });