SemanticsObject Class Reference

#import <SemanticsObject.h>

Inheritance diagram for SemanticsObject:

Instance Methods
(BOOL)	- isAccessibilityBridgeAlive
(void)	- setSemanticsNode:
(void)	- replaceChildAtIndex:withChild:
(BOOL)	- nodeWillCauseLayoutChange:
(BOOL)	- nodeWillCauseScroll:
(BOOL)	- nodeShouldTriggerAnnouncement:
(void)	- collectRoutes:
(NSString *)	- routeName
(BOOL)	- onCustomAccessibilityAction:
(void)	- accessibilityBridgeDidFinishUpdate
((unavailable("Use initWithBridge instead")	- __attribute__
(instancetype)	- initWithBridge:uid:
(BOOL)	- accessibilityScrollToVisible
(BOOL)	- accessibilityScrollToVisibleWithChild:
(id)	- _accessibilityHitTest:withEvent:

Properties
int32_t	uid
SemanticsObject *	parent
fml::WeakPtr< flutter::AccessibilityBridgeIos >	bridge
flutter::SemanticsNode	node
BOOL	hasChildren
NSArray< SemanticsObject * > *	children
NSArray< SemanticsObject * > *	childrenInHitTestOrder
id	nativeAccessibility

Detailed Description

A node in the iOS semantics tree. This object is a wrapper over a native accessibiliy object, which is stored in the property nativeAccessibility. In the most case, the nativeAccessibility directly returns this object. Some subclasses such as the FlutterScrollableSemanticsObject creates a native UIScrollView as its nativeAccessibility so that it can interact with iOS.

Definition at line 31 of file SemanticsObject.h.

Method Documentation

__attribute__

- ((unavailable("Use initWithBridge instead") __attribute__

_accessibilityHitTest:withEvent:

- (id) _accessibilityHitTest:		(CGPoint)	point
withEvent:		(UIEvent *)	event

Provided by category SemanticsObject(Tests).

accessibilityBridgeDidFinishUpdate

- (void) accessibilityBridgeDidFinishUpdate

Called after accessibility bridge finishes a semantics update.

Subclasses can override this method if they contain states that can only be updated once every node in the accessibility tree has finished updating.

Definition at line 337 of file SemanticsObject.mm.

                                           { /* Do nothing by default */
}

accessibilityScrollToVisible

- (BOOL) accessibilityScrollToVisible

Provided by category SemanticsObject(Tests).

accessibilityScrollToVisibleWithChild:

- (BOOL) accessibilityScrollToVisibleWithChild:

(id)

child

Provided by category SemanticsObject(Tests).

collectRoutes:

- (void) collectRoutes:

(NSMutableArray<SemanticsObject*>*)

edges

Definition at line 474 of file SemanticsObject.mm.

                     :(NSMutableArray<SemanticsObject*>*)edges {
  if (self.node.HasFlag(flutter::SemanticsFlags::kScopesRoute)) {
    [edges addObject:self];
  }
  if ([self hasChildren]) {
    for (SemanticsObject* child in self.children) {
      [child collectRoutes:edges];
    }
  }
}

initWithBridge:uid:

- (instancetype) initWithBridge:		(fml::WeakPtr<flutter::AccessibilityBridgeIos>)	bridge
uid:		(int32_t)	NS_DESIGNATED_INITIALIZER

Reimplemented in FlutterPlatformViewSemanticsContainer.

Definition at line 265 of file SemanticsObject.mm.

                              :(fml::WeakPtr<flutter::AccessibilityBridgeIos>)bridge
                           uid:(int32_t)uid {
  FML_DCHECK(bridge) << "bridge must be set";
  FML_DCHECK(uid >= kRootNodeId);
  // Initialize with the UIView as the container.
  // The UIView will not necessarily be accessibility parent for this object.
  // The bridge informs the OS of the actual structure via
  // `accessibilityContainer` and `accessibilityElementAtIndex`.
  self = [super initWithAccessibilityContainer:bridge->view()];
 
  if (self) {
    _bridge = bridge;
    _uid = uid;
    _children = [[NSMutableArray alloc] init];
    _childrenInHitTestOrder = [[NSArray alloc] init];
  }
 
  return self;
}

References kRootNodeId.

isAccessibilityBridgeAlive

- (BOOL) isAccessibilityBridgeAlive

Due to the fact that VoiceOver may hold onto SemanticObjects even after it shuts down, there can be situations where the AccessibilityBridge is shutdown, but the SemanticObject will still be alive. If VoiceOver is turned on again, it may try to access this orphaned SemanticObject. Methods that are called from the accessiblity framework should use this to guard against this case by just returning early if its bridge has been shutdown.

See https://github.com/flutter/flutter/issues/43795 for more information.

Definition at line 329 of file SemanticsObject.mm.

                                   {
  return self.bridge.get() != nil;
}

References bridge.

nodeShouldTriggerAnnouncement:

- (BOOL) nodeShouldTriggerAnnouncement:

(const flutter::SemanticsNode*)

node

Whether calling setSemanticsNode: with node should trigger an announcement.

Definition at line 359 of file SemanticsObject.mm.

                                     :(const flutter::SemanticsNode*)node {
  // The node dropped the live region flag, if it ever had one.
  if (!node || !node->HasFlag(flutter::SemanticsFlags::kIsLiveRegion)) {
    return NO;
  }
 
  // The node has gained a new live region flag, always announce.
  if (!self.node.HasFlag(flutter::SemanticsFlags::kIsLiveRegion)) {
    return YES;
  }
 
  // The label has updated, and the new node has a live region flag.
  return self.node.label != node->label;
}

nodeWillCauseLayoutChange:

- (BOOL) nodeWillCauseLayoutChange:

(const flutter::SemanticsNode*)

node

Whether calling setSemanticsNode: with node would cause a layout change.

Definition at line 343 of file SemanticsObject.mm.

                                 :(const flutter::SemanticsNode*)node {
  return self.node.rect != node->rect || self.node.transform != node->transform;
}

nodeWillCauseScroll:

- (BOOL) nodeWillCauseScroll:

(const flutter::SemanticsNode*)

node

Whether calling setSemanticsNode: with node would cause a scroll event.

Definition at line 350 of file SemanticsObject.mm.

                           :(const flutter::SemanticsNode*)node {
  return !isnan(self.node.scrollPosition) && !isnan(node->scrollPosition) &&
         self.node.scrollPosition != node->scrollPosition;
}

onCustomAccessibilityAction:

- (BOOL) onCustomAccessibilityAction:

(FlutterCustomAccessibilityAction*)

action

Definition at line 485 of file SemanticsObject.mm.

                                   :(FlutterCustomAccessibilityAction*)action {
  if (!self.node.HasAction(flutter::SemanticsAction::kCustomAction)) {
    return NO;
  }
  int32_t action_id = action.uid;
  std::vector<uint8_t> args;
  args.push_back(3);  // type=int32.
  args.push_back(action_id);
  args.push_back(action_id >> 8);
  args.push_back(action_id >> 16);
  args.push_back(action_id >> 24);
  self.bridge->DispatchSemanticsAction(
      self.uid, flutter::SemanticsAction::kCustomAction,
      fml::MallocMapping::Copy(args.data(), args.size() * sizeof(uint8_t)));
  return YES;
}

References FlutterCustomAccessibilityAction::uid.

replaceChildAtIndex:withChild:

- (void) replaceChildAtIndex:		(NSInteger)	index
withChild:		(SemanticsObject*)	child

Definition at line 374 of file SemanticsObject.mm.

                           :(NSInteger)index withChild:(SemanticsObject*)child {
  SemanticsObject* oldChild = _children[index];
  oldChild.parent = nil;
  child.parent = self;
  [_children replaceObjectAtIndex:index withObject:child];
}

References parent.

routeName

- (NSString *) routeName

Definition at line 381 of file SemanticsObject.mm.

                       {
  // Returns the first non-null and non-empty semantic label of a child
  // with an NamesRoute flag. Otherwise returns nil.
  if (self.node.HasFlag(flutter::SemanticsFlags::kNamesRoute)) {
    NSString* newName = self.accessibilityLabel;
    if (newName != nil && [newName length] > 0) {
      return newName;
    }
  }
  if ([self hasChildren]) {
    for (SemanticsObject* child in self.children) {
      NSString* newName = [child routeName];
      if (newName != nil && [newName length] > 0) {
        return newName;
      }
    }
  }
  return nil;
}

setSemanticsNode:

- (void) setSemanticsNode:

(const flutter::SemanticsNode*)

NS_REQUIRES_SUPER

Updates this semantics object using data from the node argument.

Definition at line 333 of file SemanticsObject.mm.

                        :(const flutter::SemanticsNode*)node {
  _node = *node;
}

Property Documentation

bridge

- (WeakPtr<)flutter:

readnonatomicassign

The accessibility bridge that this semantics object is attached to. This object may use the bridge to access contextual application information. A weak pointer is used because the platform view owns the accessibility bridge. If you are referencing this property from an iOS callback, be sure to use isAccessibilityBridgeActive to protect against the case where this node may be orphaned.

Definition at line 52 of file SemanticsObject.h.

Referenced by FLUTTER_ASSERT_ARC::ConvertPointToGlobal(), FLUTTER_ASSERT_ARC::ConvertRectToGlobal(), and isAccessibilityBridgeAlive.

children

- (NSArray<SemanticsObject*>*) children

readwritenonatomiccopy

Direct children of this semantics object. Each child's parent property must be equal to this object.

Definition at line 68 of file SemanticsObject.h.

childrenInHitTestOrder

- (NSArray<SemanticsObject*>*) childrenInHitTestOrder

readwritenonatomiccopy

Direct children of this semantics object in hit test order. Each child's parent property must be equal to this object.

Definition at line 74 of file SemanticsObject.h.

hasChildren

- (BOOL) hasChildren

readnonatomicassign

Whether this semantics object has child semantics objects.

Definition at line 62 of file SemanticsObject.h.

nativeAccessibility

- (id) nativeAccessibility

readnonatomicassign

The UIAccessibility that represents this object.

By default, this return self. Subclasses can override to return different objects to represent them. For example, FlutterScrollableSemanticsObject[s] maintain UIScrollView[s] to represent their UIAccessibility[s].

Definition at line 83 of file SemanticsObject.h.

node

- (SemanticsNode) SemanticsObject:

readnonatomicassign

The semantics node used to produce this semantics object.

Definition at line 57 of file SemanticsObject.h.

parent

- (SemanticsObject*) parent

readnonatomicweak

The parent of this node in the node tree. Will be nil for the root node and during transient state changes.

Definition at line 42 of file SemanticsObject.h.

Referenced by FLUTTER_ASSERT_ARC::GetGlobalTransform(), and replaceChildAtIndex:withChild:.

uid

- (int32_t) uid

readnonatomicassign

The globally unique identifier for this node.

Definition at line 36 of file SemanticsObject.h.

---

The documentation for this class was generated from the following files:

• shell/platform/darwin/ios/framework/Source/SemanticsObject.h
• shell/platform/darwin/ios/framework/Source/SemanticsObject.mm