patch from issue 218843002

ui/views/cull_set.h

+// Copyright (c) 2014 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 UI_VIEWS_CULL_SET_H_
+#define UI_VIEWS_CULL_SET_H_
+
+#include "base/containers/hash_tables.h"
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "ui/views/views_export.h"
+
+namespace views {
+
+class View;
+
+// A CullSet defines a set of View pointers which have been possibly culled
+// from painting or other bounds-checking operations. It wraps a set of
+// pointers to views, or NULL if no such set is available.
+class VIEWS_EXPORT CullSet {
+ public:
+  // Default constructor builds a CullSet that will always return true for
+  // ShouldPaint().
+  CullSet();
+  ~CullSet();
+
+  // Wraps a set of pointers to Views, as might be provided by
+  // gfx::RTree::Query(), that intersect the damage rect and therefore need
+  // to be painted. CullSet takes ownership of the provided pointer.
+  CullSet(scoped_ptr<base::hash_set<intptr_t> > cull_set);
+
+  // Returns true if |view| needs to be painted.
+  bool ShouldPaint(const View* view) const;
+
+ private:
+  friend class BoundsTreeTestView;
+
+  // The set of Views that collided with the query rectangle provided to the
+  // RTree data structure, or NULL if one is not available.
+  scoped_ptr<base::hash_set<intptr_t> > cull_set_;
+
+  DISALLOW_COPY_AND_ASSIGN(CullSet);
+};
+
+}  // namespace views
+
+#endif  // UI_VIEWS_CULL_SET_H_