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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
#include "TreeWalker.h"
#include "nsAccessibilityService.h"
#include "DocAccessible.h"
#include "mozilla/dom/ChildIterator.h"
#include "mozilla/dom/Element.h"
namespace mozilla::a11y {
////////////////////////////////////////////////////////////////////////////////
// TreeWalker
////////////////////////////////////////////////////////////////////////////////
TreeWalker::TreeWalker(LocalAccessible* aContext)
: mDoc(aContext->Document()),
mContext(aContext),
mAnchorNode(nullptr),
mARIAOwnsIdx(0),
mChildFilter(nsIContent::eSkipPlaceholderContent),
mFlags(0),
mPhase(eAtStart) {
mChildFilter |= nsIContent::eAllChildren;
mAnchorNode = mContext->IsDoc() ? mDoc->DocumentNode()->GetRootElement()
: mContext->GetContent();
MOZ_COUNT_CTOR(TreeWalker);
}
TreeWalker::TreeWalker(LocalAccessible* aContext, nsIContent* aAnchorNode,
uint32_t aFlags)
: mDoc(aContext->Document()),
mContext(aContext),
mAnchorNode(aAnchorNode),
mARIAOwnsIdx(0),
mChildFilter(nsIContent::eSkipPlaceholderContent),
mFlags(aFlags),
mPhase(eAtStart) {
MOZ_ASSERT(mFlags & eWalkCache,
"This constructor cannot be used for tree creation");
MOZ_ASSERT(aAnchorNode, "No anchor node for the accessible tree walker");
mChildFilter |= nsIContent::eAllChildren;
MOZ_COUNT_CTOR(TreeWalker);
}
TreeWalker::TreeWalker(DocAccessible* aDocument, nsIContent* aAnchorNode)
: mDoc(aDocument),
mContext(nullptr),
mAnchorNode(aAnchorNode),
mARIAOwnsIdx(0),
mChildFilter(nsIContent::eSkipPlaceholderContent |
nsIContent::eAllChildren),
mFlags(eWalkCache),
mPhase(eAtStart) {
MOZ_ASSERT(aAnchorNode, "No anchor node for the accessible tree walker");
MOZ_COUNT_CTOR(TreeWalker);
}
TreeWalker::~TreeWalker() { MOZ_COUNT_DTOR(TreeWalker); }
LocalAccessible* TreeWalker::Scope(nsIContent* aAnchorNode) {
Reset();
mAnchorNode = aAnchorNode;
mFlags |= eScoped;
bool skipSubtree = false;
LocalAccessible* acc = AccessibleFor(aAnchorNode, 0, &skipSubtree);
if (acc) {
mPhase = eAtEnd;
return acc;
}
return skipSubtree ? nullptr : Next();
}
bool TreeWalker::Seek(nsIContent* aChildNode) {
MOZ_ASSERT(aChildNode, "Child cannot be null");
Reset();
if (mAnchorNode == aChildNode) {
return true;
}
nsIContent* childNode = nullptr;
nsINode* parentNode = aChildNode;
do {
childNode = parentNode->AsContent();
parentNode = childNode->GetFlattenedTreeParent();
// Handle the special case of XBL binding child under a shadow root.
if (parentNode && parentNode->IsShadowRoot()) {
parentNode = childNode->GetFlattenedTreeParent();
if (parentNode == mAnchorNode) {
return true;
}
continue;
}
if (!parentNode || !parentNode->IsElement()) {
return false;
}
// If ARIA owned child.
LocalAccessible* child = mDoc->GetAccessible(childNode);
if (child && child->IsRelocated()) {
MOZ_ASSERT(
!(mFlags & eScoped),
"Walker should not be scoped when seeking into relocated children");
if (child->LocalParent() != mContext) {
return false;
}
LocalAccessible* ownedChild = nullptr;
while ((ownedChild = mDoc->ARIAOwnedAt(mContext, mARIAOwnsIdx++)) &&
ownedChild != child) {
;
}
MOZ_ASSERT(ownedChild, "A child has to be in ARIA owned elements");
mPhase = eAtARIAOwns;
return true;
}
// Look in DOM.
dom::AllChildrenIterator* iter =
PrependState(parentNode->AsElement(), true);
if (!iter->Seek(childNode)) {
return false;
}
if (parentNode == mAnchorNode) {
mPhase = eAtDOM;
return true;
}
} while (true);
MOZ_ASSERT_UNREACHABLE("because the do-while loop never breaks");
}
LocalAccessible* TreeWalker::Next() {
if (mStateStack.IsEmpty()) {
if (mPhase == eAtEnd) {
return nullptr;
}
if (mPhase == eAtDOM || mPhase == eAtARIAOwns) {
if (!(mFlags & eScoped)) {
mPhase = eAtARIAOwns;
LocalAccessible* child = mDoc->ARIAOwnedAt(mContext, mARIAOwnsIdx);
if (child) {
mARIAOwnsIdx++;
return child;
}
}
MOZ_ASSERT(!(mFlags & eScoped) || mPhase != eAtARIAOwns,
"Don't walk relocated children in scoped mode");
mPhase = eAtEnd;
return nullptr;
}
if (!mAnchorNode) {
mPhase = eAtEnd;
return nullptr;
}
mPhase = eAtDOM;
PushState(mAnchorNode, true);
}
dom::AllChildrenIterator* top = &mStateStack[mStateStack.Length() - 1];
while (top) {
while (nsIContent* childNode = top->GetNextChild()) {
bool skipSubtree = false;
LocalAccessible* child = AccessibleFor(childNode, mFlags, &skipSubtree);
if (child) {
return child;
}
// Walk down the subtree if allowed.
if (!skipSubtree && childNode->IsElement()) {
top = PushState(childNode, true);
}
}
top = PopState();
}
// If we traversed the whole subtree of the anchor node. Move to next node
// relative anchor node within the context subtree if asked.
if (mFlags != eWalkContextTree) {
// eWalkCache flag presence indicates that the search is scoped to the
// anchor (no ARIA owns stuff).
if (mFlags & eWalkCache) {
mPhase = eAtEnd;
return nullptr;
}
return Next();
}
nsINode* contextNode = mContext->GetNode();
while (mAnchorNode != contextNode) {
nsINode* parentNode = mAnchorNode->GetFlattenedTreeParent();
if (!parentNode || !parentNode->IsElement()) return nullptr;
nsIContent* parent = parentNode->AsElement();
top = PushState(parent, true);
if (top->Seek(mAnchorNode)) {
mAnchorNode = parent;
return Next();
}
// XXX We really should never get here, it means we're trying to find an
// accessible for a dom node where iterating over its parent's children
// doesn't return it. However this sometimes happens when we're asked for
// the nearest accessible to place holder content which we ignore.
mAnchorNode = parent;
}
return Next();
}
LocalAccessible* TreeWalker::Prev() {
if (mStateStack.IsEmpty()) {
if (mPhase == eAtStart || mPhase == eAtDOM) {
mPhase = eAtStart;
return nullptr;
}
if (mPhase == eAtEnd) {
if (mFlags & eScoped) {
mPhase = eAtDOM;
} else {
mPhase = eAtARIAOwns;
mARIAOwnsIdx = mDoc->ARIAOwnedCount(mContext);
}
}
if (mPhase == eAtARIAOwns) {
MOZ_ASSERT(!(mFlags & eScoped),
"Should not walk relocated children in scoped mode");
if (mARIAOwnsIdx > 0) {
return mDoc->ARIAOwnedAt(mContext, --mARIAOwnsIdx);
}
if (!mAnchorNode) {
mPhase = eAtStart;
return nullptr;
}
mPhase = eAtDOM;
PushState(mAnchorNode, false);
}
}
dom::AllChildrenIterator* top = &mStateStack[mStateStack.Length() - 1];
while (top) {
while (nsIContent* childNode = top->GetPreviousChild()) {
// No accessible creation on the way back.
bool skipSubtree = false;
LocalAccessible* child =
AccessibleFor(childNode, eWalkCache, &skipSubtree);
if (child) {
return child;
}
// Walk down into subtree to find accessibles.
if (!skipSubtree && childNode->IsElement()) {
top = PushState(childNode, false);
}
}
top = PopState();
}
// Move to a previous node relative the anchor node within the context
// subtree if asked.
if (mFlags != eWalkContextTree) {
mPhase = eAtStart;
return nullptr;
}
nsINode* contextNode = mContext->GetNode();
while (mAnchorNode != contextNode) {
nsINode* parentNode = mAnchorNode->GetFlattenedTreeParent();
if (!parentNode || !parentNode->IsElement()) {
return nullptr;
}
nsIContent* parent = parentNode->AsElement();
top = PushState(parent, true);
if (top->Seek(mAnchorNode)) {
mAnchorNode = parent;
return Prev();
}
mAnchorNode = parent;
}
mPhase = eAtStart;
return nullptr;
}
LocalAccessible* TreeWalker::AccessibleFor(nsIContent* aNode, uint32_t aFlags,
bool* aSkipSubtree) {
// Ignore the accessible and its subtree if it was repositioned by means
// of aria-owns.
LocalAccessible* child = mDoc->GetAccessible(aNode);
if (child) {
if (child->IsRelocated()) {
*aSkipSubtree = true;
return nullptr;
}
return child;
}
// Create an accessible if allowed.
if (!(aFlags & eWalkCache) && mContext->IsAcceptableChild(aNode)) {
mDoc->RelocateARIAOwnedIfNeeded(aNode);
return GetAccService()->CreateAccessible(aNode, mContext, aSkipSubtree);
}
return nullptr;
}
dom::AllChildrenIterator* TreeWalker::PopState() {
mStateStack.RemoveLastElement();
return mStateStack.IsEmpty() ? nullptr : &mStateStack.LastElement();
}
} // namespace mozilla::a11y