Calculate paint invalidation rect for scrollbars

third_party/WebKit/Source/core/paint/PaintInvalidationCapableScrollableArea.h

+// Copyright 2015 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 PaintInvalidationCapableScrollableArea_h
+#define PaintInvalidationCapableScrollableArea_h
+
+#include "core/CoreExport.h"
+#include "platform/geometry/LayoutRect.h"
+#include "platform/scroll/ScrollableArea.h"
+
+namespace blink {
+
+class LayoutBox;
+class LayoutBoxModelObject;
+class LayoutScrollbarPart;
+class PaintInvalidationContainer;
+class PaintInvalidationState;
+
+// Base class of FrameView and PaintLayerScrollableArea to share paint invalidation code.
+// TODO(wangxianzhu): Combine this into PaintLayerScrollableArea when root-layer-scrolls launches.
+class CORE_EXPORT PaintInvalidationCapableScrollableArea : public ScrollableArea {
+public:
+    void willRemoveScrollbar(Scrollbar*, ScrollbarOrientation) override;
+    void invalidatePaintOfScrollControlsIfNeeded(const PaintInvalidationState&, const LayoutBoxModelObject& paintInvalidationContainer);
+
+private:
+    virtual LayoutBox& boxForScrollControlPaintInvalidation() const = 0;
+    virtual LayoutScrollbarPart* scrollCorner() const = 0;
+    virtual LayoutScrollbarPart* resizer() const = 0;
+
+    LayoutRect m_horizontalScrollbarPreviousPaintInvalidationRect;
+    LayoutRect m_verticalScrollbarPreviousPaintInvalidationRect;
+    LayoutRect m_scrollCornerPreviousPaintInvalidationRect;
+};
+
+} // namespace blink
+
+#endif // PaintInvalidationCapableScrollableArea_h