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/size_f.h"
  10 #include "ui/gfx/vector2d_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 notify the delegate what is the upper
  21   // total scroll offset bound.
  22   virtual void SetMaxScrollOffset(const gfx::Vector2dF& max_scroll_offset) = 0;
  23
  24   // This is called by the compositor when the scroll offset of the layer would
  25   // have otherwise changed.
  26   virtual void SetTotalScrollOffset(const gfx::Vector2dF& new_value) = 0;
  27
  28   // This is called by the compositor to query the current scroll offset of the
  29   // layer.
  30   // There is no requirement that the return values of this method are
  31   // stable in time (two subsequent calls may yield different results).
  32   // The return value is not required to be related to the values passed in to
  33   // the SetTotalScrollOffset method in any way however it is required to be no
  34   // more than the value passed to the most recent SetMaxScrollOffset call.
  35   virtual gfx::Vector2dF GetTotalScrollOffset() = 0;
  36
  37   // This is called by the compositor to check whether a delegate-managed fling
  38   // is active or not.
  39   virtual bool IsExternalFlingActive() const = 0;
  40
  41   // This is called by the compositor to notify the delegate what is the current
  42   // page scale factor and limits are.
  43   virtual void SetTotalPageScaleFactorAndLimits(
  44       float page_scale_factor,
  45       float min_page_scale_factor,
  46       float max_page_scale_factor) = 0;
  47
  48   // This is called by the compositor to notify the delegate what is the layer's
  49   // scrollable size is.
  50   virtual void SetScrollableSize(const gfx::SizeF& scrollable_size) = 0;
  51
  52  protected:
  53   LayerScrollOffsetDelegate() {}
  54   virtual ~LayerScrollOffsetDelegate() {}
  55
  56  private:
  57   DISALLOW_COPY_AND_ASSIGN(LayerScrollOffsetDelegate);
  58 };
  59
  60 }  // namespace cc
  61
  62 #endif  // CC_INPUT_LAYER_SCROLL_OFFSET_DELEGATE_H_