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Diffstat (limited to '')
-rw-r--r-- | dom/base/ShadowIncludingTreeIterator.h | 118 |
1 files changed, 118 insertions, 0 deletions
diff --git a/dom/base/ShadowIncludingTreeIterator.h b/dom/base/ShadowIncludingTreeIterator.h new file mode 100644 index 0000000000..886738f39f --- /dev/null +++ b/dom/base/ShadowIncludingTreeIterator.h @@ -0,0 +1,118 @@ +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ +/* vim: set ts=8 sts=2 et sw=2 tw=80: */ +/* 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/. */ + +/** + * Implementation of + * https://dom.spec.whatwg.org/#concept-shadow-including-tree-order in iterator + * form. This can and should be used to avoid recursion on the stack and lots + * of function calls during shadow-including tree iteration. + */ + +#ifndef mozilla_dom_ShadowIncludingTreeIterator_h +#define mozilla_dom_ShadowIncludingTreeIterator_h + +#include "nsINode.h" +#include "nsTArray.h" +#include "mozilla/dom/Element.h" +#include "mozilla/dom/ShadowRoot.h" + +namespace mozilla::dom { + +class ShadowIncludingTreeIterator { + public: + /** + * Initialize an iterator with aRoot. After that it can be iterated with a + * range-based for loop. At the moment, that's the only supported form of use + * for this iterator. + */ + explicit ShadowIncludingTreeIterator(nsINode& aRoot) : mCurrent(&aRoot) { + mRoots.AppendElement(&aRoot); + } + +#ifdef DEBUG + ~ShadowIncludingTreeIterator() { + MOZ_ASSERT( + !mMutationGuard.Mutated(0), + "Don't mutate the DOM while using a ShadowIncludingTreeIterator"); + } +#endif // DEBUG + + // Basic support for range-based for loops. This will modify the iterator as + // it goes. + ShadowIncludingTreeIterator& begin() { return *this; } + + std::nullptr_t end() const { return nullptr; } + + bool operator!=(std::nullptr_t) const { return !!mCurrent; } + + explicit operator bool() const { return !!mCurrent; } + + void operator++() { Next(); } + + void SkipChildren() { + MOZ_ASSERT(mCurrent, "Shouldn't be at end"); + mCurrent = mCurrent->GetNextNonChildNode(mRoots.LastElement()); + WalkOutOfShadowRootsIfNeeded(); + } + + nsINode* operator*() { return mCurrent; } + + private: + void Next() { + MOZ_ASSERT(mCurrent, "Don't call Next() after we have no current node"); + + // We walk shadow roots immediately after their shadow host. + if (Element* element = Element::FromNode(mCurrent)) { + if (ShadowRoot* shadowRoot = element->GetShadowRoot()) { + mCurrent = shadowRoot; + mRoots.AppendElement(shadowRoot); + return; + } + } + + mCurrent = mCurrent->GetNextNode(mRoots.LastElement()); + WalkOutOfShadowRootsIfNeeded(); + } + + void WalkOutOfShadowRootsIfNeeded() { + while (!mCurrent) { + // Nothing left under this root. Keep trying to pop the stack until we + // find a node or run out of stack. + nsINode* root = mRoots.PopLastElement(); + if (mRoots.IsEmpty()) { + // No more roots to step out of; we're done. mCurrent is already set to + // null. + return; + } + mCurrent = + ShadowRoot::FromNode(root)->Host()->GetNextNode(mRoots.LastElement()); + } + } + + // The current node we're at. + nsINode* mCurrent; + + // Stack of roots that we're inside of right now. An empty stack can only + // happen when mCurrent is null (and hence we are done iterating). + // + // The default array size here is picked based on gut feeling. We want at + // least 1, since we will always add something to it in our constructor. + // Having a few more entries probably makes sense, because this is commonly + // used in cases when we know we have custom elements, and hence likely have + // shadow DOMs. But the exact value "4" was just picked because it sounded + // not too big, not too small. Feel free to replace it with something else + // based on actual data. + CopyableAutoTArray<nsINode*, 4> mRoots; + +#ifdef DEBUG + // Make sure no one mutates the DOM while we're walking over it. + nsMutationGuard mMutationGuard; +#endif // DEBUG +}; + +} // namespace mozilla::dom + +#endif // mozilla_dom_ShadowIncludingTreeIterator_h |