зеркало из https://github.com/mozilla/gecko-dev.git
114 строки
3.7 KiB
C++
114 строки
3.7 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/**
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* Implementation of
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* https://dom.spec.whatwg.org/#concept-shadow-including-tree-order in iterator
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* form. This can and should be used to avoid recursion on the stack and lots
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* of function calls during shadow-including tree iteration.
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*/
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#ifndef mozilla_dom_ShadowIncludingTreeIterator_h
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#define mozilla_dom_ShadowIncludingTreeIterator_h
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#include "nsINode.h"
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#include "nsTArray.h"
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#include "mozilla/dom/Element.h"
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#include "mozilla/dom/ShadowRoot.h"
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namespace mozilla {
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namespace dom {
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class ShadowIncludingTreeIterator {
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public:
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/**
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* Initialize an iterator with aRoot. After that it can be iterated with a
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* range-based for loop. At the moment, that's the only supported form of use
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* for this iterator.
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*/
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explicit ShadowIncludingTreeIterator(nsINode& aRoot) : mCurrent(&aRoot) {
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mRoots.AppendElement(&aRoot);
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}
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#ifdef DEBUG
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~ShadowIncludingTreeIterator() {
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MOZ_ASSERT(
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!mMutationGuard.Mutated(0),
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"Don't mutate the DOM while using a ShadowIncludingTreeIterator");
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}
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#endif // DEBUG
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// Basic support for range-based for loops. This will modify the iterator as
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// it goes.
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ShadowIncludingTreeIterator& begin() { return *this; }
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ShadowIncludingTreeIterator end() { return ShadowIncludingTreeIterator(); }
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bool operator!=(const ShadowIncludingTreeIterator& aOther) {
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return mCurrent != aOther.mCurrent;
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}
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void operator++() { Next(); }
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nsINode* operator*() { return mCurrent; }
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private:
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// Constructor used only for end() to represent a drained iterator.
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ShadowIncludingTreeIterator() : mCurrent(nullptr) {}
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void Next() {
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MOZ_ASSERT(mCurrent, "Don't call Next() after we have no current node");
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// We walk shadow roots immediately after their shadow host.
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if (Element* element = Element::FromNode(mCurrent)) {
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if (ShadowRoot* shadowRoot = element->GetShadowRoot()) {
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mCurrent = shadowRoot;
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mRoots.AppendElement(shadowRoot);
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return;
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}
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}
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mCurrent = mCurrent->GetNextNode(mRoots.LastElement());
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while (!mCurrent) {
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// Nothing left under this root. Keep trying to pop the stack until we
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// find a node or run out of stack.
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nsINode* root = mRoots.PopLastElement();
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if (mRoots.IsEmpty()) {
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// No more roots to step out of; we're done. mCurrent is already set to
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// null.
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return;
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}
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mCurrent =
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ShadowRoot::FromNode(root)->Host()->GetNextNode(mRoots.LastElement());
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}
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}
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// The current node we're at.
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nsINode* mCurrent;
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// Stack of roots that we're inside of right now. An empty stack can only
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// happen when mCurrent is null (and hence we are done iterating).
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//
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// The default array size here is picked based on gut feeling. We want at
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// least 1, since we will always add something to it in our constructor.
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// Having a few more entries probably makes sense, because this is commonly
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// used in cases when we know we have custom elements, and hence likely have
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// shadow DOMs. But the exact value "4" was just picked because it sounded
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// not too big, not too small. Feel free to replace it with something else
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// based on actual data.
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AutoTArray<nsINode*, 4> mRoots;
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#ifdef DEBUG
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// Make sure no one mutates the DOM while we're walking over it.
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nsMutationGuard mMutationGuard;
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#endif // DEBUG
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};
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} // namespace dom
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} // namespace mozilla
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#endif // mozilla_dom_ShadowIncludingTreeIterator_h
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