Add accessibilityValueDescription support. (facebook#26169)

Summary:
React Native components need a mechanism to specify their value to assistive technologies. This PR adds the notion of accessibilityValueDescription-- a property which either contains a textual description of a component's value, or for range-based components, such as sliders and progress bars, it contains range information (minimum, current, and maximum).

On iOS, the range-based info if present is converted into a percentage and added to the accessibilityValue property of the UIView. If text is present as part of the accessibilityValueDescription, it is used instead of the range-based information.

On Android, any range-based information in accessibilityValueDescription is exposed in the AccessibilityNodeInfo's RangeInfo. Text which is part of accessibilityValueDescription is appended to the content description.

## Changelog

[GENERAL] [Change] - add accessibilityValuedescription property.
Pull Request resolved: facebook#26169

Test Plan: Added two new accessibility examples to RNTester, one which uses text and another which uses range-based info in accessibilityValueDescription. Verified that they both behave correctly on both Android and iOS.

Differential Revision: D17444730

Pulled By: cpojer

fbshipit-source-id: 1fb3252a90f88f7cafe1cbf7db08c03f14cc2321

Libraries/Components/View/ReactNativeViewAttributes.js

@@ -20,6 +20,7 @@ const UIView = {
   accessibilityLiveRegion: true,
   accessibilityRole: true,
   accessibilityState: true,
+  accessibilityValue: true,
   accessibilityHint: true,
   importantForAccessibility: true,
   nativeID: true,

Libraries/Components/View/ReactNativeViewViewConfig.js

@@ -123,6 +123,7 @@ const ReactNativeViewConfig = {
     accessibilityRole: true,
     accessibilityStates: true, // TODO: Can be removed after next release
     accessibilityState: true,
+    accessibilityValue: true,
     accessibilityViewIsModal: true,
     accessible: true,
     alignContent: true,

Libraries/Components/View/ViewAccessibility.js

@@ -62,3 +62,25 @@ export type AccessibilityState = {
   busy?: boolean,
   expanded?: boolean,
 };
+
+export type AccessibilityValue = $ReadOnly<{|
+  /**
+   * The minimum value of this component's range. (should be an integer)
+   */
+  min?: number,
+
+  /**
+   * The maximum value of this component's range. (should be an integer)
+   */
+  max?: number,
+
+  /**
+   * The current value of this component's range. (should be an integer)
+   */
+  now?: number,
+
+  /**
+   * A textual description of this component's value. (will override minimum, current, and maximum if set)
+   */
+  text?: string,
+|}>;

Libraries/Components/View/ViewPropTypes.js

@@ -18,6 +18,7 @@ import type {TVViewProps} from '../AppleTV/TVViewPropTypes';
 import type {
   AccessibilityRole,
   AccessibilityState,
+  AccessibilityValue,
   AccessibilityActionEvent,
   AccessibilityActionInfo,
 } from './ViewAccessibility';
@@ -413,6 +414,7 @@ export type ViewProps = $ReadOnly<{|
    * Indicates to accessibility services that UI Component is in a specific State.
    */
   accessibilityState?: ?AccessibilityState,
+  accessibilityValue?: ?AccessibilityValue,
 
   /**
    * Provides an array of custom actions available for accessibility.

Libraries/DeprecatedPropTypes/DeprecatedViewPropTypes.js

@@ -102,6 +102,7 @@ module.exports = {
   >),
 
   accessibilityState: PropTypes.object,
+  accessibilityValue: PropTypes.object,
   /**
    * Indicates to accessibility services whether the user should be notified
    * when this view changes. Works for Android API >= 19 only.

RNTester/js/examples/Accessibility/AccessibilityExample.js

@@ -512,6 +512,89 @@ class AccessibilityActionsExample extends React.Component {
     );
   }
 }
+
+class FakeSliderExample extends React.Component {
+  state = {
+    current: 50,
+    textualValue: 'center',
+  };
+
+  increment = () => {
+    let newValue = this.state.current + 2;
+    if (newValue > 100) {
+      newValue = 100;
+    }
+    this.setState({
+      current: newValue,
+    });
+  };
+
+  decrement = () => {
+    let newValue = this.state.current - 2;
+    if (newValue < 0) {
+      newValue = 0;
+    }
+    this.setState({
+      current: newValue,
+    });
+  };
+
+  render() {
+    return (
+      <View>
+        <View
+          accessible={true}
+          accessibilityLabel="Fake Slider"
+          accessibilityRole="adjustable"
+          accessibilityActions={[{name: 'increment'}, {name: 'decrement'}]}
+          onAccessibilityAction={event => {
+            switch (event.nativeEvent.actionName) {
+              case 'increment':
+                this.increment();
+                break;
+              case 'decrement':
+                this.decrement();
+                break;
+            }
+          }}
+          accessibilityValue={{
+            min: 0,
+            now: this.state.current,
+            max: 100,
+          }}>
+          <Text>Fake Slider</Text>
+        </View>
+        <View
+          accessible={true}
+          accessibilityLabel="Equalizer"
+          accessibilityRole="adjustable"
+          accessibilityActions={[{name: 'increment'}, {name: 'decrement'}]}
+          onAccessibilityAction={event => {
+            switch (event.nativeEvent.actionName) {
+              case 'increment':
+                if (this.state.textualValue === 'center') {
+                  this.setState({textualValue: 'right'});
+                } else if (this.state.textualValue === 'left') {
+                  this.setState({textualValue: 'center'});
+                }
+                break;
+              case 'decrement':
+                if (this.state.textualValue === 'center') {
+                  this.setState({textualValue: 'left'});
+                } else if (this.state.textualValue === 'right') {
+                  this.setState({textualValue: 'center'});
+                }
+                break;
+            }
+          }}
+          accessibilityValue={{text: this.state.textualValue}}>
+          <Text>Equalizer</Text>
+        </View>
+      </View>
+    );
+  }
+}
+
 class ScreenReaderStatusExample extends React.Component<{}> {
   state = {
     screenReaderEnabled: false,
@@ -591,6 +674,12 @@ exports.examples = [
       return <AccessibilityActionsExample />;
     },
   },
+  {
+    title: 'Fake Slider Example',
+    render(): React.Element<typeof FakeSliderExample> {
+      return <FakeSliderExample />;
+    },
+  },
   {
     title: 'Check if the screen reader is enabled',
     render(): React.Element<typeof ScreenReaderStatusExample> {

React/Views/RCTView.m

@@ -271,6 +271,26 @@ - (NSString *)accessibilityValue
       [valueComponents addObject:stateDescriptions[@"busy"]];
     }
   }
+
+  // handle accessibilityValue
+
+  if (self.accessibilityValueInternal) {
+    id min = self.accessibilityValueInternal[@"min"];
+    id now = self.accessibilityValueInternal[@"now"];
+    id max = self.accessibilityValueInternal[@"max"];
+    id text = self.accessibilityValueInternal[@"text"];
+    if (text && [text isKindOfClass:[NSString class]]) {
+      [valueComponents addObject:text];
+    } else if ([min isKindOfClass:[NSNumber class]] &&
+        [now isKindOfClass:[NSNumber class]] &&
+        [max isKindOfClass:[NSNumber class]] &&
+        ([min intValue] < [max intValue]) &&
+        ([min intValue] <= [now intValue] && [now intValue] <= [max intValue])) {
+      int val = ([now intValue]*100)/([max intValue]-[min intValue]);
+      [valueComponents addObject:[NSString stringWithFormat:@"%d percent", val]];
+    }
+  }
+
   if (valueComponents.count > 0) {
     return [valueComponents componentsJoinedByString:@", "];
   }

React/Views/RCTViewManager.m

@@ -126,6 +126,7 @@ - (RCTShadowView *)shadowView
 RCT_REMAP_VIEW_PROPERTY(accessibilityActions, reactAccessibilityElement.accessibilityActions, NSDictionaryArray)
 RCT_REMAP_VIEW_PROPERTY(accessibilityLabel, reactAccessibilityElement.accessibilityLabel, NSString)
 RCT_REMAP_VIEW_PROPERTY(accessibilityHint, reactAccessibilityElement.accessibilityHint, NSString)
+RCT_REMAP_VIEW_PROPERTY(accessibilityValue, reactAccessibilityElement.accessibilityValueInternal, NSDictionary)
 RCT_REMAP_VIEW_PROPERTY(accessibilityViewIsModal, reactAccessibilityElement.accessibilityViewIsModal, BOOL)
 RCT_REMAP_VIEW_PROPERTY(accessibilityElementsHidden, reactAccessibilityElement.accessibilityElementsHidden, BOOL)
 RCT_REMAP_VIEW_PROPERTY(accessibilityIgnoresInvertColors, reactAccessibilityElement.shouldAccessibilityIgnoresInvertColors, BOOL)

React/Views/UIView+React.h

@@ -119,6 +119,7 @@
 @property (nonatomic, copy) NSString *accessibilityRole;
 @property (nonatomic, copy) NSDictionary<NSString *, id> *accessibilityState;
 @property (nonatomic, copy) NSArray <NSDictionary *> *accessibilityActions;
+@property (nonatomic, copy) NSDictionary *accessibilityValueInternal;
 
 /**
  * Used in debugging to get a description of the view hierarchy rooted at

React/Views/UIView+React.m

@@ -327,8 +327,16 @@ - (void)setAccessibilityState:(NSDictionary<NSString *, id> *)accessibilityState
   objc_setAssociatedObject(self, @selector(accessibilityState), accessibilityState, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
 }
 
-#pragma mark - Debug
+- (NSDictionary<NSString *, id> *)accessibilityValueInternal
+{
+  return objc_getAssociatedObject(self, _cmd);
+}
+- (void)setAccessibilityValueInternal:(NSDictionary<NSString *, id> *)accessibilityValue
+{
+  objc_setAssociatedObject(self, @selector(accessibilityValueInternal), accessibilityValue, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
+}
 
+#pragma mark - Debug
 - (void)react_addRecursiveDescriptionToString:(NSMutableString *)string atLevel:(NSUInteger)level
 {
   for (NSUInteger i = 0; i < level; i++) {

ReactAndroid/src/main/java/com/facebook/react/uimanager/BaseViewManager.java

@@ -179,6 +179,7 @@ private void updateViewContentDescription(@NonNull T view) {
     final ReadableMap accessibilityState = (ReadableMap) view.getTag(R.id.accessibility_state);
     final String accessibilityHint = (String) view.getTag(R.id.accessibility_hint);
     final List<String> contentDescription = new ArrayList<>();
+    final ReadableMap accessibilityValue = (ReadableMap) view.getTag(R.id.accessibility_value);
     if (accessibilityLabel != null) {
       contentDescription.add(accessibilityLabel);
     }
@@ -205,6 +206,12 @@ private void updateViewContentDescription(@NonNull T view) {
         }
       }
     }
+    if (accessibilityValue != null && accessibilityValue.hasKey("text")) {
+      final Dynamic text = accessibilityValue.getDynamic("text");
+      if (text != null && text.getType() == ReadableType.String) {
+        contentDescription.add(text.asString());
+      }
+    }
     if (accessibilityHint != null) {
       contentDescription.add(accessibilityHint);
     }
@@ -223,6 +230,18 @@ public void setAccessibilityActions(T view, ReadableArray accessibilityActions)
     view.setTag(R.id.accessibility_actions, accessibilityActions);
   }
 
+  @ReactProp(name = ViewProps.ACCESSIBILITY_VALUE)
+  public void setAccessibilityValue(T view, ReadableMap accessibilityValue) {
+    if (accessibilityValue == null) {
+      return;
+    }
+
+    view.setTag(R.id.accessibility_value, accessibilityValue);
+    if (accessibilityValue.hasKey("text")) {
+      updateViewContentDescription(view);
+    }
+  }
+
   @Override
   @ReactProp(name = ViewProps.IMPORTANT_FOR_ACCESSIBILITY)
   public void setImportantForAccessibility(