cc/input/layer_scroll_offset_delegate.h

   1 // Copyright 2013 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 CC_INPUT_LAYER_SCROLL_OFFSET_DELEGATE_H_
   6 #define CC_INPUT_LAYER_SCROLL_OFFSET_DELEGATE_H_
   7
   8 #include "base/basictypes.h"
   9 #include "ui/gfx/vector2d_f.h"
  10
  11 namespace cc {
  12
  13 // The LayerScrollOffsetDelegate allows for the embedder to take ownership of
  14 // the scroll offset of the root layer.
  15 //
  16 // The LayerScrollOffsetDelegate is only used on the impl thread.
  17 class LayerScrollOffsetDelegate {
  18  public:
  19   // This is called by the compositor when the scroll offset of the layer would
  20   // have otherwise changed.
  21   virtual void SetTotalScrollOffset(gfx::Vector2dF new_value) = 0;
  22
  23   // This is called by the compositor to query the current scroll offset of the
  24   // layer.
  25   // There is no requirement that the return values of this method are
  26   // stable in time (two subsequent calls may yield different results).
  27   // The return value is not required to be related to the values passed in to
  28   // the SetTotalScrollOffset method in any way.
  29   virtual gfx::Vector2dF GetTotalScrollOffset() = 0;
  30
  31  protected:
  32   LayerScrollOffsetDelegate() {}
  33   virtual ~LayerScrollOffsetDelegate() {}
  34
  35  private:
  36   DISALLOW_COPY_AND_ASSIGN(LayerScrollOffsetDelegate);
  37 };
  38
  39 }  // namespace cc
  40
  41 #endif  // CC_INPUT_LAYER_SCROLL_OFFSET_DELEGATE_H_