ui/accessibility/ax_tree.cc - chromium/src - Git at Google

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 #include "ui/accessibility/ax_tree.h"

 #include <set>

 #include "base/logging.h"
 #include "base/strings/stringprintf.h"
 #include "ui/accessibility/ax_node.h"

 namespace ui {

 namespace {

 std::string TreeToStringHelper(AXNode* node, int indent) {
   std::string result = std::string(2 * indent, ' ');
   result += node->data().ToString() + "\n";
   for (int i = 0; i < node->child_count(); ++i)
     result += TreeToStringHelper(node->ChildAtIndex(i), indent + 1);
   return result;
 }

 }  // namespace

 // Intermediate state to keep track of during a tree update.
 struct AXTreeUpdateState {
   AXTreeUpdateState() : new_root(nullptr) {}

   // During an update, this keeps track of all nodes that have been
   // implicitly referenced as part of this update, but haven't been
   // updated yet. It's an error if there are any pending nodes at the
   // end of Unserialize.
   std::set<AXNode*> pending_nodes;

   // Keeps track of new nodes created during this update.
   std::set<AXNode*> new_nodes;

   // The new root in this update, if any.
   AXNode* new_root;
 };

 AXTreeDelegate::AXTreeDelegate() {
 }

 AXTreeDelegate::~AXTreeDelegate() {
 }

 AXTree::AXTree()
     : delegate_(NULL), root_(NULL) {
   AXNodeData root;
   root.id = -1;
   root.role = AX_ROLE_ROOT_WEB_AREA;

   AXTreeUpdate initial_state;
   initial_state.nodes.push_back(root);
   CHECK(Unserialize(initial_state)) << error();
 }

 AXTree::AXTree(const AXTreeUpdate& initial_state)
     : delegate_(NULL), root_(NULL) {
   CHECK(Unserialize(initial_state)) << error();
 }

 AXTree::~AXTree() {
   if (root_)
     DestroyNodeAndSubtree(root_, nullptr);
 }

 void AXTree::SetDelegate(AXTreeDelegate* delegate) {
   delegate_ = delegate;
 }

 AXNode* AXTree::GetFromId(int32 id) const {
   base::hash_map<int32, AXNode*>::const_iterator iter = id_map_.find(id);
   return iter != id_map_.end() ? iter->second : NULL;
 }

 bool AXTree::Unserialize(const AXTreeUpdate& update) {
   AXTreeUpdateState update_state;
   int32 old_root_id = root_ ? root_->id() : 0;

   if (update.node_id_to_clear != 0) {
     AXNode* node = GetFromId(update.node_id_to_clear);
     if (!node) {
       error_ = base::StringPrintf("Bad node_id_to_clear: %d",
                                   update.node_id_to_clear);
       return false;
     }
     if (node == root_) {
       DestroySubtree(root_, &update_state);
       root_ = NULL;
     } else {
       for (int i = 0; i < node->child_count(); ++i)
         DestroySubtree(node->ChildAtIndex(i), &update_state);
       std::vector<AXNode*> children;
       node->SwapChildren(children);
       update_state.pending_nodes.insert(node);
     }
   }

   for (size_t i = 0; i < update.nodes.size(); ++i) {
     if (!UpdateNode(update.nodes[i], &update_state))
       return false;
   }

   if (!update_state.pending_nodes.empty()) {
     error_ = "Nodes left pending by the update:";
     for (std::set<AXNode*>::iterator iter = update_state.pending_nodes.begin();
          iter != update_state.pending_nodes.end(); ++iter) {
       error_ += base::StringPrintf(" %d", (*iter)->id());
     }
     return false;
   }

   if (delegate_) {
     std::set<AXNode*>& new_nodes = update_state.new_nodes;
     std::vector<AXTreeDelegate::Change> changes;
     changes.reserve(update.nodes.size());
     for (size_t i = 0; i < update.nodes.size(); ++i) {
       AXNode* node = GetFromId(update.nodes[i].id);
       if (new_nodes.find(node) != new_nodes.end()) {
         if (new_nodes.find(node->parent()) == new_nodes.end()) {
           changes.push_back(
               AXTreeDelegate::Change(node, AXTreeDelegate::SUBTREE_CREATED));
         } else {
           changes.push_back(
               AXTreeDelegate::Change(node, AXTreeDelegate::NODE_CREATED));
         }
       } else {
         changes.push_back(
             AXTreeDelegate::Change(node, AXTreeDelegate::NODE_CHANGED));
       }
     }
     delegate_->OnAtomicUpdateFinished(root_->id() != old_root_id, changes);
   }

   return true;
 }

 std::string AXTree::ToString() const {
   return TreeToStringHelper(root_, 0);
 }

 AXNode* AXTree::CreateNode(AXNode* parent, int32 id, int32 index_in_parent) {
   AXNode* new_node = new AXNode(parent, id, index_in_parent);
   id_map_[new_node->id()] = new_node;
   if (delegate_)
     delegate_->OnNodeCreated(new_node);
   return new_node;
 }

 bool AXTree::UpdateNode(const AXNodeData& src,
                         AXTreeUpdateState* update_state) {
   // This method updates one node in the tree based on serialized data
   // received in an AXTreeUpdate. See AXTreeUpdate for pre and post
   // conditions.

   // Look up the node by id. If it's not found, then either the root
   // of the tree is being swapped, or we're out of sync with the source
   // and this is a serious error.
   AXNode* node = GetFromId(src.id);
   if (node) {
     update_state->pending_nodes.erase(node);
     node->SetData(src);
   } else {
     if (src.role != AX_ROLE_ROOT_WEB_AREA) {
       error_ = base::StringPrintf(
           "%d is not in the tree and not the new root", src.id);
       return false;
     }
     if (update_state->new_root) {
       error_ = "Tree update contains two new roots";
       return false;
     }

     update_state->new_root = CreateNode(NULL, src.id, 0);
     node = update_state->new_root;
     update_state->new_nodes.insert(node);
     node->SetData(src);
   }

   if (delegate_)
     delegate_->OnNodeChanged(node);

   // First, delete nodes that used to be children of this node but aren't
   // anymore.
   if (!DeleteOldChildren(node, src.child_ids, update_state)) {
     if (update_state->new_root)
       DestroySubtree(update_state->new_root, update_state);
     return false;
   }

   // Now build a new children vector, reusing nodes when possible,
   // and swap it in.
   std::vector<AXNode*> new_children;
   bool success = CreateNewChildVector(
       node, src.child_ids, &new_children, update_state);
   node->SwapChildren(new_children);

   // Update the root of the tree if needed.
   if (src.role == AX_ROLE_ROOT_WEB_AREA &&
       (!root_ || root_->id() != src.id)) {
     if (root_)
       DestroySubtree(root_, update_state);
     root_ = node;
   }

   return success;
 }

 void AXTree::DestroySubtree(AXNode* node,
                             AXTreeUpdateState* update_state) {
   if (delegate_)
     delegate_->OnSubtreeWillBeDeleted(node);
   DestroyNodeAndSubtree(node, update_state);
 }

 void AXTree::DestroyNodeAndSubtree(AXNode* node,
                                    AXTreeUpdateState* update_state) {
   id_map_.erase(node->id());
   for (int i = 0; i < node->child_count(); ++i)
     DestroyNodeAndSubtree(node->ChildAtIndex(i), update_state);
   if (delegate_)
     delegate_->OnNodeWillBeDeleted(node);
   if (update_state) {
     update_state->pending_nodes.erase(node);
   }
   node->Destroy();
 }

 bool AXTree::DeleteOldChildren(AXNode* node,
                                const std::vector<int32>& new_child_ids,
                                AXTreeUpdateState* update_state) {
   // Create a set of child ids in |src| for fast lookup, and return false
   // if a duplicate is found;
   std::set<int32> new_child_id_set;
   for (size_t i = 0; i < new_child_ids.size(); ++i) {
     if (new_child_id_set.find(new_child_ids[i]) != new_child_id_set.end()) {
       error_ = base::StringPrintf("Node %d has duplicate child id %d",
                                   node->id(), new_child_ids[i]);
       return false;
     }
     new_child_id_set.insert(new_child_ids[i]);
   }

   // Delete the old children.
   const std::vector<AXNode*>& old_children = node->children();
   for (size_t i = 0; i < old_children.size(); ++i) {
     int old_id = old_children[i]->id();
     if (new_child_id_set.find(old_id) == new_child_id_set.end())
       DestroySubtree(old_children[i], update_state);
   }

   return true;
 }

 bool AXTree::CreateNewChildVector(AXNode* node,
                                   const std::vector<int32>& new_child_ids,
                                   std::vector<AXNode*>* new_children,
                                   AXTreeUpdateState* update_state) {
   bool success = true;
   for (size_t i = 0; i < new_child_ids.size(); ++i) {
     int32 child_id = new_child_ids[i];
     int32 index_in_parent = static_cast<int32>(i);
     AXNode* child = GetFromId(child_id);
     if (child) {
       if (child->parent() != node) {
         // This is a serious error - nodes should never be reparented.
         // If this case occurs, continue so this node isn't left in an
         // inconsistent state, but return failure at the end.
         error_ = base::StringPrintf(
             "Node %d reparented from %d to %d",
             child->id(),
             child->parent() ? child->parent()->id() : 0,
             node->id());
         success = false;
         continue;
       }
       child->SetIndexInParent(index_in_parent);
     } else {
       child = CreateNode(node, child_id, index_in_parent);
       update_state->pending_nodes.insert(child);
       update_state->new_nodes.insert(child);
     }
     new_children->push_back(child);
   }

   return success;
 }

 }  // namespace ui
	// Copyright 2013 The Chromium Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	#include "ui/accessibility/ax_tree.h"

	#include <set>

	#include "base/logging.h"
	#include "base/strings/stringprintf.h"
	#include "ui/accessibility/ax_node.h"

	namespace ui {

	namespace {

	std::string TreeToStringHelper(AXNode* node, int indent) {
	std::string result = std::string(2 * indent, ' ');
	result += node->data().ToString() + "\n";
	for (int i = 0; i < node->child_count(); ++i)
	result += TreeToStringHelper(node->ChildAtIndex(i), indent + 1);
	return result;
	}

	} // namespace

	// Intermediate state to keep track of during a tree update.
	struct AXTreeUpdateState {
	AXTreeUpdateState() : new_root(nullptr) {}

	// During an update, this keeps track of all nodes that have been
	// implicitly referenced as part of this update, but haven't been
	// updated yet. It's an error if there are any pending nodes at the
	// end of Unserialize.
	std::set<AXNode*> pending_nodes;

	// Keeps track of new nodes created during this update.
	std::set<AXNode*> new_nodes;

	// The new root in this update, if any.
	AXNode* new_root;
	};

	AXTreeDelegate::AXTreeDelegate() {
	}

	AXTreeDelegate::~AXTreeDelegate() {
	}

	AXTree::AXTree()
	: delegate_(NULL), root_(NULL) {
	AXNodeData root;
	root.id = -1;
	root.role = AX_ROLE_ROOT_WEB_AREA;

	AXTreeUpdate initial_state;
	initial_state.nodes.push_back(root);
	CHECK(Unserialize(initial_state)) << error();
	}

	AXTree::AXTree(const AXTreeUpdate& initial_state)
	: delegate_(NULL), root_(NULL) {
	CHECK(Unserialize(initial_state)) << error();
	}

	AXTree::~AXTree() {
	if (root_)
	DestroyNodeAndSubtree(root_, nullptr);
	}

	void AXTree::SetDelegate(AXTreeDelegate* delegate) {
	delegate_ = delegate;
	}

	AXNode* AXTree::GetFromId(int32 id) const {
	base::hash_map<int32, AXNode*>::const_iterator iter = id_map_.find(id);
	return iter != id_map_.end() ? iter->second : NULL;
	}

	bool AXTree::Unserialize(const AXTreeUpdate& update) {
	AXTreeUpdateState update_state;
	int32 old_root_id = root_ ? root_->id() : 0;

	if (update.node_id_to_clear != 0) {
	AXNode* node = GetFromId(update.node_id_to_clear);
	if (!node) {
	error_ = base::StringPrintf("Bad node_id_to_clear: %d",
	update.node_id_to_clear);
	return false;
	}
	if (node == root_) {
	DestroySubtree(root_, &update_state);
	root_ = NULL;
	} else {
	for (int i = 0; i < node->child_count(); ++i)
	DestroySubtree(node->ChildAtIndex(i), &update_state);
	std::vector<AXNode*> children;
	node->SwapChildren(children);
	update_state.pending_nodes.insert(node);
	}
	}

	for (size_t i = 0; i < update.nodes.size(); ++i) {
	if (!UpdateNode(update.nodes[i], &update_state))
	return false;
	}

	if (!update_state.pending_nodes.empty()) {
	error_ = "Nodes left pending by the update:";
	for (std::set<AXNode*>::iterator iter = update_state.pending_nodes.begin();
	iter != update_state.pending_nodes.end(); ++iter) {
	error_ += base::StringPrintf(" %d", (*iter)->id());
	}
	return false;
	}

	if (delegate_) {
	std::set<AXNode*>& new_nodes = update_state.new_nodes;
	std::vector<AXTreeDelegate::Change> changes;
	changes.reserve(update.nodes.size());
	for (size_t i = 0; i < update.nodes.size(); ++i) {
	AXNode* node = GetFromId(update.nodes[i].id);
	if (new_nodes.find(node) != new_nodes.end()) {
	if (new_nodes.find(node->parent()) == new_nodes.end()) {
	changes.push_back(
	AXTreeDelegate::Change(node, AXTreeDelegate::SUBTREE_CREATED));
	} else {
	changes.push_back(
	AXTreeDelegate::Change(node, AXTreeDelegate::NODE_CREATED));
	}
	} else {
	changes.push_back(
	AXTreeDelegate::Change(node, AXTreeDelegate::NODE_CHANGED));
	}
	}
	delegate_->OnAtomicUpdateFinished(root_->id() != old_root_id, changes);
	}

	return true;
	}

	std::string AXTree::ToString() const {
	return TreeToStringHelper(root_, 0);
	}

	AXNode* AXTree::CreateNode(AXNode* parent, int32 id, int32 index_in_parent) {
	AXNode* new_node = new AXNode(parent, id, index_in_parent);
	id_map_[new_node->id()] = new_node;
	if (delegate_)
	delegate_->OnNodeCreated(new_node);
	return new_node;
	}

	bool AXTree::UpdateNode(const AXNodeData& src,
	AXTreeUpdateState* update_state) {
	// This method updates one node in the tree based on serialized data
	// received in an AXTreeUpdate. See AXTreeUpdate for pre and post
	// conditions.

	// Look up the node by id. If it's not found, then either the root
	// of the tree is being swapped, or we're out of sync with the source
	// and this is a serious error.
	AXNode* node = GetFromId(src.id);
	if (node) {
	update_state->pending_nodes.erase(node);
	node->SetData(src);
	} else {
	if (src.role != AX_ROLE_ROOT_WEB_AREA) {
	error_ = base::StringPrintf(
	"%d is not in the tree and not the new root", src.id);
	return false;
	}
	if (update_state->new_root) {
	error_ = "Tree update contains two new roots";
	return false;
	}

	update_state->new_root = CreateNode(NULL, src.id, 0);
	node = update_state->new_root;
	update_state->new_nodes.insert(node);
	node->SetData(src);
	}

	if (delegate_)
	delegate_->OnNodeChanged(node);

	// First, delete nodes that used to be children of this node but aren't
	// anymore.
	if (!DeleteOldChildren(node, src.child_ids, update_state)) {
	if (update_state->new_root)
	DestroySubtree(update_state->new_root, update_state);
	return false;
	}

	// Now build a new children vector, reusing nodes when possible,
	// and swap it in.
	std::vector<AXNode*> new_children;
	bool success = CreateNewChildVector(
	node, src.child_ids, &new_children, update_state);
	node->SwapChildren(new_children);

	// Update the root of the tree if needed.
	if (src.role == AX_ROLE_ROOT_WEB_AREA &&
	(!root_ \|\| root_->id() != src.id)) {
	if (root_)
	DestroySubtree(root_, update_state);
	root_ = node;
	}

	return success;
	}

	void AXTree::DestroySubtree(AXNode* node,
	AXTreeUpdateState* update_state) {
	if (delegate_)
	delegate_->OnSubtreeWillBeDeleted(node);
	DestroyNodeAndSubtree(node, update_state);
	}

	void AXTree::DestroyNodeAndSubtree(AXNode* node,
	AXTreeUpdateState* update_state) {
	id_map_.erase(node->id());
	for (int i = 0; i < node->child_count(); ++i)
	DestroyNodeAndSubtree(node->ChildAtIndex(i), update_state);
	if (delegate_)
	delegate_->OnNodeWillBeDeleted(node);
	if (update_state) {
	update_state->pending_nodes.erase(node);
	}
	node->Destroy();
	}

	bool AXTree::DeleteOldChildren(AXNode* node,
	const std::vector<int32>& new_child_ids,
	AXTreeUpdateState* update_state) {
	// Create a set of child ids in \|src\| for fast lookup, and return false
	// if a duplicate is found;
	std::set<int32> new_child_id_set;
	for (size_t i = 0; i < new_child_ids.size(); ++i) {
	if (new_child_id_set.find(new_child_ids[i]) != new_child_id_set.end()) {
	error_ = base::StringPrintf("Node %d has duplicate child id %d",
	node->id(), new_child_ids[i]);
	return false;
	}
	new_child_id_set.insert(new_child_ids[i]);
	}

	// Delete the old children.
	const std::vector<AXNode*>& old_children = node->children();
	for (size_t i = 0; i < old_children.size(); ++i) {
	int old_id = old_children[i]->id();
	if (new_child_id_set.find(old_id) == new_child_id_set.end())
	DestroySubtree(old_children[i], update_state);
	}

	return true;
	}

	bool AXTree::CreateNewChildVector(AXNode* node,
	const std::vector<int32>& new_child_ids,
	std::vector<AXNode> new_children,
	AXTreeUpdateState* update_state) {
	bool success = true;
	for (size_t i = 0; i < new_child_ids.size(); ++i) {
	int32 child_id = new_child_ids[i];
	int32 index_in_parent = static_cast<int32>(i);
	AXNode* child = GetFromId(child_id);
	if (child) {
	if (child->parent() != node) {
	// This is a serious error - nodes should never be reparented.
	// If this case occurs, continue so this node isn't left in an
	// inconsistent state, but return failure at the end.
	error_ = base::StringPrintf(
	"Node %d reparented from %d to %d",
	child->id(),
	child->parent() ? child->parent()->id() : 0,
	node->id());
	success = false;
	continue;
	}
	child->SetIndexInParent(index_in_parent);
	} else {
	child = CreateNode(node, child_id, index_in_parent);
	update_state->pending_nodes.insert(child);
	update_state->new_nodes.insert(child);
	}
	new_children->push_back(child);
	}

	return success;
	}

	} // namespace ui