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Diffstat (limited to '')
| -rw-r--r-- | accessible/base/TreeWalker.cpp | 348 |
1 files changed, 348 insertions, 0 deletions
diff --git a/accessible/base/TreeWalker.cpp b/accessible/base/TreeWalker.cpp new file mode 100644 index 0000000000..ff314bd83c --- /dev/null +++ b/accessible/base/TreeWalker.cpp @@ -0,0 +1,348 @@ +/* -*- 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 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +#include "TreeWalker.h" + +#include "nsAccessibilityService.h" +#include "DocAccessible.h" + +#include "mozilla/dom/ChildIterator.h" +#include "mozilla/dom/Element.h" + +using namespace mozilla; +using 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)) { + // We may have ARIA owned element in the dependent attributes map, but the + // element may be not allowed for this ARIA owns relation, if the relation + // crosses out XBL anonymous content boundaries. In this case we won't + // create an accessible object for it, when aria-owns is processed, which + // may make the element subtree inaccessible. To avoid that let's create + // an accessible object now, and later, if allowed, move it in the tree, + // when aria-owns relation is processed. + if (mDoc->RelocateARIAOwnedIfNeeded(aNode) && !aNode->IsXULElement()) { + *aSkipSubtree = true; + return nullptr; + } + return GetAccService()->CreateAccessible(aNode, mContext, aSkipSubtree); + } + + return nullptr; +} + +dom::AllChildrenIterator* TreeWalker::PopState() { + mStateStack.RemoveLastElement(); + return mStateStack.IsEmpty() ? nullptr : &mStateStack.LastElement(); +} |