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