Isolation of subtrees of stacking contexts and out-of-flow positioned objects

third_party/WebKit/Source/platform/graphics/paint/PaintPropertyNode.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef PaintPropertyNode_h
+#define PaintPropertyNode_h
+
+#include "wtf/PassRefPtr.h"
+#include "wtf/RefCounted.h"
+#include "wtf/RefPtr.h"
+
+namespace blink {
+
+template <typename T>
+class PaintPropertyNode : public RefCounted<T> {
+public:
+    // Parent property node, or nullptr if this is the root property.
+    const T* parent() const { return m_parent.get(); }
+    // Used to move this node from one tree to another.
+    void setParent(PassRefPtr<T> parent) { m_parent = parent; }
+
+    // See PaintPropertyTreeBuilder for explanation of isolation.
+    bool isIsolationNode() const { return m_isIsolationNode; }
+    void setIsIsolationNode() { m_isIsolationNode = true; }
+
+    // This node or ancestor of this node that is not an isolation node.
+    // This is for PaintArtifactCompositor to ignore isolation nodes.
+    // TODO(wangxianzhu): This might be unnecessary when PaintArtifactCompositor
+    // fully works. For now this avoids extra layers for isolation nodes and
+    // pixel differences of layout tests caused by unknown reasons.
+    const T* nonIsolationNode() const
+    {
+        const T* node = static_cast<const T*>(this);
+        while (node && node->isIsolationNode())
+            node = node->parent();
+        return node;
+    }
+
+    // Parent non-isolation property node, or nullptr if this is the root property.
+    // This is for PaintArtifactCompositor to ignore isolation nodes.
+    const T* nonIsolationParent() const
+    {
+        return m_parent ? m_parent->nonIsolationNode() : nullptr;
+    }
+
+protected:
+    PaintPropertyNode() : m_isIsolationNode(false) { }
+    PaintPropertyNode(PassRefPtr<T> parent) : m_parent(parent), m_isIsolationNode(false) { }
+
+private:
+    RefPtr<T> m_parent;
+    bool m_isIsolationNode;
+};
+
+} // namespace blink
+
+#endif // PaintPropertyNode_h