chromium/third_party/blink/renderer/core/css/style_traversal_root.h

// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_CSS_STYLE_TRAVERSAL_ROOT_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_CSS_STYLE_TRAVERSAL_ROOT_H_

#include "base/dcheck_is_on.h"
#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/core/dom/container_node.h"

namespace blink {

// Class used to represent a common ancestor for all dirty nodes in a DOM tree.
// Subclasses implement the various types of dirtiness for style recalc, style
// invalidation, and layout tree rebuild. The common ancestor is used as a
// starting point for traversal to avoid unnecessary DOM tree traversal.
//
// The first dirty node is stored as a single root. When a second node is
// added with a common child-dirty ancestor which is not dirty, we store that
// as a common root. Any subsequent dirty nodes added whose closest child-dirty
// ancestor is not itself dirty, or is the current root, will cause us to fall
// back to use the document as the root node. In order to find a lowest common
// ancestor we would have had to traverse up the ancestor chain to see if we are
// below the current common root or not.
//
// Note that when the common ancestor candidate passed into Update is itself
// dirty, we know that we are currently below the current root node and don't
// have to modify it.

class CORE_EXPORT StyleTraversalRoot { … };

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_CSS_STYLE_TRAVERSAL_ROOT_H_