blob: 58f590be22dc0eb90d1601bc85631123ee5f08a4 [file] [log] [blame]
// 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 <stddef.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) {}
// Returns whether this update changes |node|.
bool HasChangedNode(const AXNode* node) {
return changed_node_ids.find(node->id()) != changed_node_ids.end();
}
// Returns whether this update removes |node|.
bool HasRemovedNode(const AXNode* node) {
return removed_node_ids.find(node->id()) != removed_node_ids.end();
}
// 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;
// This is similar to above, but we store node ids here because this list gets
// generated before any nodes get created or re-used. Its purpose is to allow
// us to know what nodes will be updated so we can make more intelligent
// decisions about when to notify delegates of removals or reparenting.
std::set<int> changed_node_ids;
// 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;
// Keeps track of any nodes removed. Used to identify re-parented nodes.
std::set<int> removed_node_ids;
};
AXTreeDelegate::AXTreeDelegate() {
}
AXTreeDelegate::~AXTreeDelegate() {
}
AXTree::AXTree()
: delegate_(NULL), root_(NULL) {
AXNodeData root;
root.id = -1;
AXTreeUpdate initial_state;
initial_state.root_id = -1;
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_t id) const {
base::hash_map<int32_t, AXNode*>::const_iterator iter = id_map_.find(id);
return iter != id_map_.end() ? iter->second : NULL;
}
void AXTree::UpdateData(const AXTreeData& data) {
data_ = data;
if (delegate_)
delegate_->OnTreeDataChanged(this);
}
bool AXTree::Unserialize(const AXTreeUpdate& update) {
AXTreeUpdateState update_state;
int32_t old_root_id = root_ ? root_->id() : 0;
// First, make a note of any nodes we will touch as part of this update.
for (size_t i = 0; i < update.nodes.size(); ++i)
update_state.changed_node_ids.insert(update.nodes[i].id);
if (update.has_tree_data)
UpdateData(update.tree_data);
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_) {
// Clear root_ before calling DestroySubtree so that root_ doesn't
// ever point to an invalid node.
AXNode* old_root = root_;
root_ = nullptr;
DestroySubtree(old_root, &update_state);
} 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);
}
}
bool root_exists = GetFromId(update.root_id) != nullptr;
for (size_t i = 0; i < update.nodes.size(); ++i) {
bool is_new_root = !root_exists && update.nodes[i].id == update.root_id;
if (!UpdateNode(update.nodes[i], is_new_root, &update_state))
return false;
}
if (!root_) {
error_ = "Tree has no root.";
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);
bool is_new_node = new_nodes.find(node) != new_nodes.end();
bool is_reparented_node =
is_new_node && update_state.HasRemovedNode(node);
AXTreeDelegate::ChangeType change = AXTreeDelegate::NODE_CHANGED;
if (is_new_node) {
bool is_subtree = new_nodes.find(node->parent()) == new_nodes.end();
if (is_reparented_node) {
change = is_subtree ? AXTreeDelegate::SUBTREE_REPARENTED
: AXTreeDelegate::NODE_REPARENTED;
} else {
change = is_subtree ? AXTreeDelegate::SUBTREE_CREATED
: AXTreeDelegate::NODE_CREATED;
}
}
changes.push_back(AXTreeDelegate::Change(node, change));
}
delegate_->OnAtomicUpdateFinished(
this, root_->id() != old_root_id, changes);
}
return true;
}
std::string AXTree::ToString() const {
return "AXTree" + data_.ToString() + "\n" + TreeToStringHelper(root_, 0);
}
AXNode* AXTree::CreateNode(AXNode* parent,
int32_t id,
int32_t index_in_parent,
AXTreeUpdateState* update_state) {
AXNode* new_node = new AXNode(parent, id, index_in_parent);
id_map_[new_node->id()] = new_node;
if (delegate_) {
if (update_state->HasChangedNode(new_node) &&
!update_state->HasRemovedNode(new_node))
delegate_->OnNodeCreated(this, new_node);
else
delegate_->OnNodeReparented(this, new_node);
}
return new_node;
}
bool AXTree::UpdateNode(const AXNodeData& src,
bool is_new_root,
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);
if (delegate_ &&
update_state->new_nodes.find(node) == update_state->new_nodes.end())
delegate_->OnNodeDataWillChange(this, node->data(), src);
node->SetData(src);
} else {
if (!is_new_root) {
error_ = base::StringPrintf(
"%d is not in the tree and not the new root", src.id);
return false;
}
update_state->new_root = CreateNode(NULL, src.id, 0, update_state);
node = update_state->new_root;
update_state->new_nodes.insert(node);
node->SetData(src);
}
if (delegate_)
delegate_->OnNodeChanged(this, 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 (is_new_root) {
// Make sure root_ always points to something valid or null_, even inside
// DestroySubtree.
AXNode* old_root = root_;
root_ = node;
if (old_root)
DestroySubtree(old_root, update_state);
}
return success;
}
void AXTree::DestroySubtree(AXNode* node,
AXTreeUpdateState* update_state) {
DCHECK(update_state);
if (delegate_) {
if (!update_state->HasChangedNode(node))
delegate_->OnSubtreeWillBeDeleted(this, node);
else
delegate_->OnSubtreeWillBeReparented(this, node);
}
DestroyNodeAndSubtree(node, update_state);
}
void AXTree::DestroyNodeAndSubtree(AXNode* node,
AXTreeUpdateState* update_state) {
if (delegate_) {
if (!update_state || !update_state->HasChangedNode(node))
delegate_->OnNodeWillBeDeleted(this, node);
else
delegate_->OnNodeWillBeReparented(this, node);
}
id_map_.erase(node->id());
for (int i = 0; i < node->child_count(); ++i)
DestroyNodeAndSubtree(node->ChildAtIndex(i), update_state);
if (update_state) {
update_state->pending_nodes.erase(node);
update_state->removed_node_ids.insert(node->id());
}
node->Destroy();
}
bool AXTree::DeleteOldChildren(AXNode* node,
const std::vector<int32_t>& 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_t> 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_t>& 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_t child_id = new_child_ids[i];
int32_t index_in_parent = static_cast<int32_t>(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);
update_state->pending_nodes.insert(child);
update_state->new_nodes.insert(child);
}
new_children->push_back(child);
}
return success;
}
} // namespace ui