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-rw-r--r--dom/base/ShadowIncludingTreeIterator.h118
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diff --git a/dom/base/ShadowIncludingTreeIterator.h b/dom/base/ShadowIncludingTreeIterator.h
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+/* -*- 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