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/geometry/scroll_offset.h"
  10 #include "ui/gfx/geometry/size_f.h"
  11
  12 namespace cc {
  13
  14 // The LayerScrollOffsetDelegate allows for the embedder to take ownership of
  15 // the scroll offset of the root layer.
  16 //
  17 // The LayerScrollOffsetDelegate is only used on the impl thread.
  18 class LayerScrollOffsetDelegate {
  19  public:
  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 however it is required to be no
  26   // more than the value passed to the most recent SetMaxScrollOffset call.
  27   virtual gfx::ScrollOffset GetTotalScrollOffset() = 0;
  28
  29   // This is called by the compositor to notify the delegate of any change to
  30   // the following parameters:
  31   // |total_scroll_offset| current scroll offset of the root layer,
  32   // |max_scroll_offset| total scroll offset upper bound for the root layer,
  33   // |scrollable_size| root layer scrollable size,
  34   // |page_scale_factor| current page scale,
  35   // |min_page_scale_factor| page scale lower limit,
  36   // |max_page_scale_factor| page scale upper limit.
  37   virtual void UpdateRootLayerState(
  38       const gfx::ScrollOffset& total_scroll_offset,
  39       const gfx::ScrollOffset& max_scroll_offset,
  40       const gfx::SizeF& scrollable_size,
  41       float page_scale_factor,
  42       float min_page_scale_factor,
  43       float max_page_scale_factor) = 0;
  44
  45   // This is called by the compositor to check whether a delegate-managed fling
  46   // is active or not.
  47   virtual bool IsExternalFlingActive() const = 0;
  48
  49  protected:
  50   LayerScrollOffsetDelegate() {}
  51   virtual ~LayerScrollOffsetDelegate() {}
  52
  53  private:
  54   DISALLOW_COPY_AND_ASSIGN(LayerScrollOffsetDelegate);
  55 };
  56
  57 }  // namespace cc
  58
  59 #endif  // CC_INPUT_LAYER_SCROLL_OFFSET_DELEGATE_H_