accessible/base/TreeWalker.cpp

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 #include "TreeWalker.h"
   7
   8 #include "Accessible.h"
   9 #include "nsAccessibilityService.h"
  10 #include "DocAccessible.h"
  11
  12 #include "mozilla/dom/ChildIterator.h"
  13 #include "mozilla/dom/Element.h"
  14
  15 using namespace mozilla::a11y;
  16
  17 ////////////////////////////////////////////////////////////////////////////////
  18 // WalkState
  19 ////////////////////////////////////////////////////////////////////////////////
  20
  21 namespace mozilla {
  22 namespace a11y {
  23
  24 struct WalkState
  25 {
  26   WalkState(nsIContent *aContent, uint32_t aFilter) :
  27     content(aContent), prevState(nullptr), iter(aContent, aFilter) {}
  28
  29   nsCOMPtr<nsIContent> content;
  30   WalkState *prevState;
  31   dom::AllChildrenIterator iter;
  32 };
  33
  34 } // namespace a11y
  35 } // namespace mozilla
  36
  37 ////////////////////////////////////////////////////////////////////////////////
  38 // TreeWalker
  39 ////////////////////////////////////////////////////////////////////////////////
  40
  41 TreeWalker::
  42   TreeWalker(Accessible* aContext, nsIContent* aContent, uint32_t aFlags) :
  43   mDoc(aContext->Document()), mContext(aContext),
  44   mFlags(aFlags), mState(nullptr)
  45 {
  46   NS_ASSERTION(aContent, "No node for the accessible tree walker!");
  47
  48   mChildFilter = mContext->CanHaveAnonChildren() ?
  49     nsIContent::eAllChildren : nsIContent::eAllButXBL;
  50   mChildFilter |= nsIContent::eSkipPlaceholderContent;
  51
  52   if (aContent)
  53     mState = new WalkState(aContent, mChildFilter);
  54
  55   MOZ_COUNT_CTOR(TreeWalker);
  56 }
  57
  58 TreeWalker::~TreeWalker()
  59 {
  60   // Clear state stack from memory
  61   while (mState)
  62     PopState();
  63
  64   MOZ_COUNT_DTOR(TreeWalker);
  65 }
  66
  67 ////////////////////////////////////////////////////////////////////////////////
  68 // TreeWalker: private
  69
  70 Accessible*
  71 TreeWalker::NextChildInternal(bool aNoWalkUp)
  72 {
  73   if (!mState || !mState->content)
  74     return nullptr;
  75
  76   while (nsIContent* childNode = mState->iter.GetNextChild()) {
  77     bool isSubtreeHidden = false;
  78     Accessible* accessible = mFlags & eWalkCache ?
  79       mDoc->GetAccessible(childNode) :
  80       GetAccService()->GetOrCreateAccessible(childNode, mContext,
  81                                              &isSubtreeHidden);
  82
  83     if (accessible)
  84       return accessible;
  85
  86     // Walk down into subtree to find accessibles.
  87     if (!isSubtreeHidden && childNode->IsElement()) {
  88       PushState(childNode);
  89       accessible = NextChildInternal(true);
  90       if (accessible)
  91         return accessible;
  92     }
  93   }
  94
  95   // No more children, get back to the parent.
  96   nsIContent* anchorNode = mState->content;
  97   PopState();
  98   if (aNoWalkUp)
  99     return nullptr;
 100
 101   if (mState)
 102     return NextChildInternal(false);
 103
 104   // If we traversed the whole subtree of the anchor node. Move to next node
 105   // relative anchor node within the context subtree if possible.
 106   if (mFlags != eWalkContextTree)
 107     return nullptr;
 108
 109   while (anchorNode != mContext->GetNode()) {
 110     nsINode* parentNode = anchorNode->GetFlattenedTreeParent();
 111     if (!parentNode || !parentNode->IsElement())
 112       return nullptr;
 113
 114     PushState(parentNode->AsElement());
 115     while (nsIContent* childNode = mState->iter.GetNextChild()) {
 116       if (childNode == anchorNode)
 117         return NextChildInternal(false);
 118     }
 119     PopState();
 120
 121     anchorNode = parentNode->AsElement();
 122   }
 123
 124   return nullptr;
 125 }
 126
 127 void
 128 TreeWalker::PopState()
 129 {
 130   WalkState* prevToLastState = mState->prevState;
 131   delete mState;
 132   mState = prevToLastState;
 133 }
 134
 135 void
 136 TreeWalker::PushState(nsIContent* aContent)
 137 {
 138   WalkState* nextToLastState = new WalkState(aContent, mChildFilter);
 139   nextToLastState->prevState = mState;
 140   mState = nextToLastState;
 141 }