import FIREFOX_52_6_0esr_RELEASE from mozilla-esr52 hg repo

accessible/base/TreeWalker.cpp

@@ -0,0 +1,325 @@
+/* -*- 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 "Accessible.h"
+#include "AccIterator.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(Accessible* aContext) :
+  mDoc(aContext->Document()), mContext(aContext), mAnchorNode(nullptr),
+  mARIAOwnsIdx(0),
+  mChildFilter(nsIContent::eSkipPlaceholderContent), mFlags(0),
+  mPhase(eAtStart)
+{
+  mChildFilter |= mContext->NoXBLKids() ?
+    nsIContent::eAllButXBL : nsIContent::eAllChildren;
+
+  mAnchorNode = mContext->IsDoc() ?
+    mDoc->DocumentNode()->GetRootElement() : mContext->GetContent();
+
+  MOZ_COUNT_CTOR(TreeWalker);
+}
+
+TreeWalker::
+  TreeWalker(Accessible* 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 |= mContext->NoXBLKids() ?
+    nsIContent::eAllButXBL : nsIContent::eAllChildren;
+
+  MOZ_COUNT_CTOR(TreeWalker);
+}
+
+TreeWalker::~TreeWalker()
+{
+  MOZ_COUNT_DTOR(TreeWalker);
+}
+
+Accessible*
+TreeWalker::Scope(nsIContent* aAnchorNode)
+{
+  Reset();
+
+  mAnchorNode = aAnchorNode;
+
+  bool skipSubtree = false;
+  Accessible* 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->HasFlag(NODE_MAY_BE_IN_BINDING_MNGR) &&
+      (mChildFilter & nsIContent::eAllButXBL) ?
+      childNode->GetParentNode() : childNode->GetFlattenedTreeParent();
+
+    if (!parentNode || !parentNode->IsElement()) {
+      return false;
+    }
+
+    // If ARIA owned child.
+    Accessible* child = mDoc->GetAccessible(childNode);
+    if (child && child->IsRelocated()) {
+      if (child->Parent() != mContext) {
+        return false;
+      }
+
+      Accessible* 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);
+
+  return false;
+}
+
+Accessible*
+TreeWalker::Next()
+{
+  if (mStateStack.IsEmpty()) {
+    if (mPhase == eAtEnd) {
+      return nullptr;
+    }
+
+    if (mPhase == eAtDOM || mPhase == eAtARIAOwns) {
+      mPhase = eAtARIAOwns;
+      Accessible* child = mDoc->ARIAOwnedAt(mContext, mARIAOwnsIdx);
+      if (child) {
+        mARIAOwnsIdx++;
+        return child;
+      }
+      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;
+      Accessible* 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();
+}
+
+Accessible*
+TreeWalker::Prev()
+{
+  if (mStateStack.IsEmpty()) {
+    if (mPhase == eAtStart || mPhase == eAtDOM) {
+      mPhase = eAtStart;
+      return nullptr;
+    }
+
+    if (mPhase == eAtEnd) {
+      mARIAOwnsIdx = mDoc->ARIAOwnedCount(mContext);
+      mPhase = eAtARIAOwns;
+    }
+
+    if (mPhase == eAtARIAOwns) {
+      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;
+      Accessible* 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;
+}
+
+Accessible*
+TreeWalker::AccessibleFor(nsIContent* aNode, uint32_t aFlags, bool* aSkipSubtree)
+{
+  // Ignore the accessible and its subtree if it was repositioned by means
+  // of aria-owns.
+  Accessible* 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()
+{
+  size_t length = mStateStack.Length();
+  mStateStack.RemoveElementAt(length - 1);
+  return mStateStack.IsEmpty() ? nullptr : &mStateStack.LastElement();
+}