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Move node implementation to Objective C (#2652)
* Move node implementation to Objective C This changes AccessibilityBridge::Node (C++) to be AccessibilityNode (objc) in order to have the nodes returned directly as ui accessibility elements. This buys us a few things: 1) We can now return an element tree instead of a flat list, thus negating the need to maintain a global rect and global translation 2) We use less memory since we don't need to instantiate both nodes and their ensuing accessibility elements 3) accessibility elements can now implement the methods necessary to respond to events like user scrolling https://github.com/flutter/flutter/issues/1664
This commit is contained in:
Todd Volkert
parent
7af714532d
commit
fdc0b71889
@ -22,6 +22,36 @@
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#include "third_party/skia/include/core/SkRect.h"
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#include "third_party/skia/include/utils/SkMatrix44.h"
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namespace sky {
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namespace shell {
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class AccessibilityBridge;
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}
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}
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@interface AccessibilityNode : NSObject
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/**
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* The globally unique identifier for this node.
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*/
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@property(nonatomic, readonly) uint32_t uid;
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/**
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* The parent of this node in the node tree. Will be nil for the root node and
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* during transient state changes.
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*/
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@property(nonatomic, readonly) AccessibilityNode* parent;
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/**
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* This node's children in the node tree.
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*/
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@property(nonatomic, readonly) NSArray<AccessibilityNode*>* children;
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- (instancetype)init __attribute__((unavailable("Use initWithBridge instead")));
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- (instancetype)initWithBridge:(sky::shell::AccessibilityBridge*)bridge
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uid:(uint32_t)uid NS_DESIGNATED_INITIALIZER;
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@end
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namespace sky {
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namespace shell {
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@ -38,21 +68,18 @@ class AccessibilityBridge final : public semantics::SemanticsListener {
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~AccessibilityBridge() override;
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void UpdateSemanticsTree(mojo::Array<semantics::SemanticsNodePtr>) override;
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AccessibilityNode* UpdateNode(const semantics::SemanticsNodePtr& node);
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void RemoveNode(AccessibilityNode* node);
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base::WeakPtr<AccessibilityBridge> AsWeakPtr();
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FlutterView* getView() { return view_; }
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private:
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class Node;
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scoped_refptr<Node> UpdateNode(const semantics::SemanticsNodePtr& node);
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void RemoveNode(scoped_refptr<Node> node);
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NSArray* CreateAccessibleElements() const NS_RETURNS_RETAINED;
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// See class docs above about ownership relationship
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FlutterView* view_;
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semantics::SemanticsServerPtr semantics_server_;
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std::map<long, scoped_refptr<Node>> nodes_;
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NSMutableDictionary<NSNumber*, AccessibilityNode*>* nodes_;
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mojo::StrongBinding<semantics::SemanticsListener> binding_;
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@ -4,15 +4,14 @@
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#include "sky/shell/platform/ios/framework/Source/accessibility_bridge.h"
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#include <UIKit/UIKit.h>
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#import <UIKit/UIKit.h>
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#include "mojo/public/cpp/application/connect.h"
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namespace sky {
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namespace shell {
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namespace {
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static const uint32_t RootNodeId = 0;
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// Contains better abstractions than the raw Mojo data structure
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struct Geometry {
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Geometry& operator=(const semantics::SemanticGeometryPtr& other) {
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@ -23,163 +22,163 @@ struct Geometry {
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return *this;
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}
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SkMatrix44 transform;
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SkMatrix44 transform =
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SkMatrix44(SkMatrix44::Identity_Constructor::kIdentity_Constructor);
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SkRect rect;
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};
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} // anonymous namespace
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// Class that holds information about accessibility nodes, which are used
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// to construct iOS accessibility elements
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class AccessibilityBridge::Node final
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: public base::RefCounted<AccessibilityBridge::Node> {
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public:
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static const uint32_t kUninitializedNodeId = -1;
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@implementation AccessibilityNode {
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sky::shell::AccessibilityBridge* _bridge;
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Node(AccessibilityBridge*, const semantics::SemanticsNodePtr&);
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void Update(const semantics::SemanticsNodePtr& node);
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void PopulateAccessibleElements(NSMutableArray* accessibleElements);
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uint32_t id_ = kUninitializedNodeId;
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std::vector<scoped_refptr<Node>> children_;
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Node* parent_ = nullptr;
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private:
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friend class base::RefCounted<Node>;
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~Node();
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void ValidateGlobalRect();
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void ValidateGlobalTransform();
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AccessibilityBridge* bridge_;
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semantics::SemanticFlagsPtr flags_;
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semantics::SemanticStringsPtr strings_;
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Geometry geometry_;
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std::unique_ptr<SkMatrix44> global_transform_;
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std::unique_ptr<SkRect> global_rect_;
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DISALLOW_COPY_AND_ASSIGN(Node);
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};
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AccessibilityBridge::Node::Node(AccessibilityBridge* bridge,
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const semantics::SemanticsNodePtr& node)
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: bridge_(bridge) {
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Update(node);
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semantics::SemanticFlagsPtr _flags;
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semantics::SemanticStringsPtr _strings;
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Geometry _geometry;
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}
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void AccessibilityBridge::Node::Update(
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const semantics::SemanticsNodePtr& node) {
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if (id_ == kUninitializedNodeId) {
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id_ = node->id;
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}
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DCHECK(id_ == node->id);
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#pragma mark - Override base class designated initializers
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if (!node->flags.is_null()) {
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flags_ = node->flags.Pass();
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// Method declared as unavailable in the interface
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- (instancetype)init {
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[self release];
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[super doesNotRecognizeSelector:_cmd];
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return nil;
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}
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#pragma mark - Designated initializers
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- (instancetype)initWithBridge:(sky::shell::AccessibilityBridge*)bridge
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uid:(uint32_t)uid {
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DCHECK(bridge != nil) << "bridge must be set";
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DCHECK(uid >= RootNodeId);
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self = [super init];
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if (self) {
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_bridge = bridge;
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_uid = uid;
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}
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if (!node->strings.is_null()) {
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strings_ = node->strings.Pass();
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return self;
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}
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#pragma mark - Semantics node methods
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- (void)update:(const semantics::SemanticsNodePtr&)mojoNode {
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DCHECK(_uid == mojoNode->id);
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if (!mojoNode->flags.is_null()) {
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_flags = mojoNode->flags.Pass();
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}
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if (!node->geometry.is_null()) {
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geometry_ = node->geometry.Pass();
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if (!mojoNode->strings.is_null()) {
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_strings = mojoNode->strings.Pass();
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}
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if (!node->children.is_null()) {
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// Mark children for removal
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for (scoped_refptr<Node> child : children_) {
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DCHECK(child->parent_ != nullptr);
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child->parent_ = nullptr;
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if (!mojoNode->geometry.is_null()) {
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_geometry = mojoNode->geometry;
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}
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if (!mojoNode->children.is_null()) {
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// Mark existing children as orphans
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NSArray* oldChildren = _children;
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for (AccessibilityNode* child in oldChildren) {
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DCHECK(child->_parent != nil);
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child->_parent = nil;
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}
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// Set the new list of children
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std::vector<scoped_refptr<Node>> children;
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for (const semantics::SemanticsNodePtr& childNode : node->children) {
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scoped_refptr<Node> child = bridge_->UpdateNode(childNode);
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child->parent_ = this;
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children.push_back(child);
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NSMutableArray* children = [[NSMutableArray alloc] init];
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_children = children;
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for (const semantics::SemanticsNodePtr& mojoChild : mojoNode->children) {
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AccessibilityNode* child = _bridge->UpdateNode(mojoChild);
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child->_parent = self;
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[children insertObject:child atIndex:0];
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}
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children.swap(children_);
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// Remove those children that are still marked for removal
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for (scoped_refptr<Node> child : children) {
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if (child->parent_ == nullptr) {
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bridge_->RemoveNode(child);
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// Remove those children that are still marked as orphans
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for (AccessibilityNode* child in oldChildren) {
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if (child->_parent == nil) {
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_bridge->RemoveNode(child);
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}
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}
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}
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global_transform_.release();
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global_rect_.release();
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}
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void AccessibilityBridge::Node::ValidateGlobalTransform() {
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if (global_transform_ != nullptr) {
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return;
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}
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if (parent_ == nullptr) {
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global_transform_.reset(new SkMatrix44(geometry_.transform));
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} else {
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parent_->ValidateGlobalTransform();
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global_transform_.reset(
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new SkMatrix44(geometry_.transform * *(parent_->global_transform_)));
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[oldChildren release];
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}
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}
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void AccessibilityBridge::Node::ValidateGlobalRect() {
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if (global_rect_ != nullptr) {
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return;
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}
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- (void)remove {
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_parent = nil;
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_bridge->RemoveNode(self);
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}
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ValidateGlobalTransform();
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#pragma mark - UIAccessibility overrides
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- (BOOL)isAccessibilityElement {
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// Per UIAccessibilityContainer, accessibility containers MUST return
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// NO to -isAccessibilityElement
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return (_children.count == 0);
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}
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- (NSString*)accessibilityLabel {
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return (_strings.is_null() || _strings->label.get().empty())
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? nil
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: @(_string->label.data());
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}
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- (UIAccessibilityTraits)accessibilityTraits {
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// TODO(tvolkert): We need more semantic info in the mojom definition
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// in order to distinguish buttons, links, sliders, etc.
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return _flags->canBeTapped ? UIAccessibilityTraitButton
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: UIAccessibilityTraitNone;
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}
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- (CGRect)accessibilityFrame {
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SkPoint quad[4];
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geometry_.rect.toQuad(quad);
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_geometry.rect.toQuad(quad);
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for (auto& point : quad) {
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SkScalar vector[4] = {point.x(), point.y(), 0, 1};
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global_transform_->mapScalars(vector);
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_geometry.transform.mapScalars(vector);
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point.set(vector[0], vector[1]);
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}
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global_rect_.reset(new SkRect());
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global_rect_.get()->set(quad, 4);
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SkRect result;
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result.set(quad, 4);
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return CGRectMake(result.x(), result.y(), result.width(), result.height());
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}
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void AccessibilityBridge::Node::PopulateAccessibleElements(
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NSMutableArray* accessibleElements) {
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if (!geometry_.rect.isEmpty()) {
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UIAccessibilityElement* element = [[UIAccessibilityElement alloc]
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initWithAccessibilityContainer:bridge_->view_];
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element.isAccessibilityElement = YES;
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ValidateGlobalRect();
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element.accessibilityFrame =
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CGRectMake(global_rect_->x(), global_rect_->y(), global_rect_->width(),
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global_rect_->height());
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if (flags_->canBeTapped) {
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// TODO(tvolkert): What about links? We need semantic info in the mojom
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// definition
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element.accessibilityTraits = UIAccessibilityTraitButton;
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}
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if (!strings_->label.get().empty()) {
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element.accessibilityLabel =
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[NSString stringWithUTF8String:strings_->label.data()];
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}
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[accessibleElements insertObject:element atIndex:0];
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[element release];
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}
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#pragma mark - UIAccessibilityElement protocol
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for (scoped_refptr<Node> child : children_) {
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child->PopulateAccessibleElements(accessibleElements);
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}
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- (id)accessibilityContainer {
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return (_uid == RootNodeId) ? _bridge->getView() : _parent;
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}
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AccessibilityBridge::Node::~Node() {}
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#pragma mark - UIAccessibilityContainer overrides
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- (NSInteger)accessibilityElementCount {
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return _children.count;
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}
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- (nullable id)accessibilityElementAtIndex:(NSInteger)index {
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return (index < 0 || index >= (NSInteger)_children.count ? nil
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: _children[index]);
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}
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- (NSInteger)indexOfAccessibilityElement:(id)element {
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return (_children == nil) ? NSNotFound : [_children indexOfObject:element];
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}
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#pragma mark - Misc
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- (void)dealloc {
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[_children release];
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[super dealloc];
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}
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@end
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#pragma mark - AccessibilityBridge impl
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namespace sky {
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namespace shell {
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AccessibilityBridge::AccessibilityBridge(FlutterView* view,
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mojo::ServiceProvider* serviceProvider)
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@ -188,17 +187,19 @@ AccessibilityBridge::AccessibilityBridge(FlutterView* view,
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mojo::InterfaceHandle<semantics::SemanticsListener> listener;
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binding_.Bind(&listener);
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semantics_server_->AddSemanticsListener(listener.Pass());
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nodes_ = [[NSMutableDictionary alloc] init];
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}
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void AccessibilityBridge::UpdateSemanticsTree(
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mojo::Array<semantics::SemanticsNodePtr> nodes) {
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for (const semantics::SemanticsNodePtr& node : nodes) {
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UpdateNode(node);
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mojo::Array<semantics::SemanticsNodePtr> mojoNodes) {
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for (const semantics::SemanticsNodePtr& mojoNode : mojoNodes) {
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auto node = UpdateNode(mojoNode);
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if (mojoNode->id == RootNodeId && view_.accessibilityElements == nil) {
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view_.accessibilityElements = @[ node ];
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}
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}
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NSArray* accessibleElements = CreateAccessibleElements();
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view_.accessibilityElements = accessibleElements;
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[accessibleElements release];
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DCHECK(view_.accessibilityElements != nil);
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UIAccessibilityPostNotification(UIAccessibilityLayoutChangedNotification,
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nil);
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@ -208,45 +209,33 @@ base::WeakPtr<AccessibilityBridge> AccessibilityBridge::AsWeakPtr() {
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return weak_factory_.GetWeakPtr();
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}
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scoped_refptr<AccessibilityBridge::Node> AccessibilityBridge::UpdateNode(
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const semantics::SemanticsNodePtr& node) {
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scoped_refptr<Node> persistentNode;
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const auto& iter = nodes_.find(node->id);
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if (iter == nodes_.end()) {
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persistentNode = new Node(this, node);
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nodes_[node->id] = persistentNode;
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} else {
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persistentNode = iter->second;
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persistentNode->Update(node);
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AccessibilityNode* AccessibilityBridge::UpdateNode(
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const semantics::SemanticsNodePtr& mojoNode) {
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AccessibilityNode* node = nodes_[@(mojoNode->id)];
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if (node == nil) {
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node = [[AccessibilityNode alloc] initWithBridge:this uid:mojoNode->id];
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DCHECK(nodes_ != nil);
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nodes_[@(mojoNode->id)] = node;
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[node release];
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}
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DCHECK(persistentNode != nullptr);
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return persistentNode;
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[node update:mojoNode];
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return node;
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}
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void AccessibilityBridge::RemoveNode(scoped_refptr<Node> node) {
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DCHECK(nodes_.find(node->id_) != nodes_.end());
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DCHECK(nodes_.at(node->id_)->parent_ == nullptr);
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nodes_.erase(node->id_);
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for (scoped_refptr<Node>& child : node->children_) {
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child->parent_ = nullptr;
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RemoveNode(child);
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void AccessibilityBridge::RemoveNode(AccessibilityNode* node) {
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[node retain];
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DCHECK(nodes_[@(node.uid)] != nil);
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DCHECK(nodes_[@(node.uid)].parent == nil);
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[nodes_ removeObjectForKey:@(node.uid)];
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for (AccessibilityNode* child in node.children) {
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[child remove];
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}
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[node release];
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}
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NSArray* AccessibilityBridge::CreateAccessibleElements() const
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NS_RETURNS_RETAINED {
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NSMutableArray* accessibleElements = [[NSMutableArray alloc] init];
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for (const auto& iter : nodes_) {
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// TODO(tvolkert): There should only ever be 1 root. Keep a reference
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// to it so we don't have to look for it here.
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if (iter.second->parent_ == nullptr) {
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iter.second->PopulateAccessibleElements(accessibleElements);
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}
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}
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return accessibleElements;
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AccessibilityBridge::~AccessibilityBridge() {
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[nodes_ release];
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}
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AccessibilityBridge::~AccessibilityBridge() {}
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} // namespace shell
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} // namespace sky
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