ui/compositor/layer_owner.h

   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
  13 namespace ui {
  14
  15 class 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_