layer_owner.h revision 5821806d5e7f356e8fa4b058a389a808ea183019 
1// Copyright (c) 2012 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef UI_COMPOSITOR_LAYER_OWNER_H_
6#define UI_COMPOSITOR_LAYER_OWNER_H_
7
8#include "base/compiler_specific.h"
9#include "base/memory/scoped_ptr.h"
10#include "ui/compositor/compositor_export.h"
11#include "ui/compositor/layer.h"
12
13namespace ui {
14
15class COMPOSITOR_EXPORT LayerOwner {
16 public:
17  LayerOwner();
18  virtual ~LayerOwner();
19
20  // Releases the owning reference to its layer, and returns it.
21  // This is used when you need to animate the presentation of the owner just
22  // prior to destroying it. The Owner can be destroyed soon after calling this
23  // function, and the caller is then responsible for disposing of the layer
24  // once any animation completes. Note that layer() will remain valid until the
25  // end of ~LayerOwner().
26  Layer* AcquireLayer() WARN_UNUSED_RESULT;
27
28  ui::Layer* layer() { return layer_; }
29  const ui::Layer* layer() const { return layer_; }
30
31 protected:
32  // The LayerOwner owns its layer unless ownership is relinquished via a call
33  // to AcquireLayer(). After that moment |layer_| will still be valid but
34  // |layer_owner_| will be NULL. The reason for releasing ownership is that
35  // the client may wish to animate the layer beyond the lifetime of the owner,
36  // e.g. fading it out when it is destroyed.
37  scoped_ptr<Layer> layer_owner_;
38  Layer* layer_;
39
40 private:
41  DISALLOW_COPY_AND_ASSIGN(LayerOwner);
42};
43
44}  // namespace ui
45
46#endif  // UI_COMPOSITOR_LAYER_OWNER_H_
47