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 "base/callback_forward.h"
  10 #include "base/time/time.h"
  11 #include "ui/gfx/geometry/scroll_offset.h"
  12 #include "ui/gfx/geometry/size_f.h"
  13
  14 namespace cc {
  15
  16 // The LayerScrollOffsetDelegate allows for the embedder to take ownership of
  17 // the scroll offset of the root layer.
  18 //
  19 // The LayerScrollOffsetDelegate is only used on the impl thread.
  20 class LayerScrollOffsetDelegate {
  21  public:
  22   // This is called by the compositor to query the current scroll offset of the
  23   // layer.
  24   // There is no requirement that the return values of this method are
  25   // stable in time (two subsequent calls may yield different results).
  26   // The return value is not required to be related to the values passed in to
  27   // the SetTotalScrollOffset method in any way however it is required to be no
  28   // more than the value passed to the most recent SetMaxScrollOffset call.
  29   virtual gfx::ScrollOffset GetTotalScrollOffset() = 0;
  30
  31   // This is called by the compositor to notify the delegate of any change to
  32   // the following parameters:
  33   // |total_scroll_offset| current scroll offset of the root layer,
  34   // |max_scroll_offset| total scroll offset upper bound for the root layer,
  35   // |scrollable_size| root layer scrollable size,
  36   // |page_scale_factor| current page scale,
  37   // |min_page_scale_factor| page scale lower limit,
  38   // |max_page_scale_factor| page scale upper limit.
  39   virtual void UpdateRootLayerState(
  40       const gfx::ScrollOffset& total_scroll_offset,
  41       const gfx::ScrollOffset& max_scroll_offset,
  42       const gfx::SizeF& scrollable_size,
  43       float page_scale_factor,
  44       float min_page_scale_factor,
  45       float max_page_scale_factor) = 0;
  46
  47   // This is called by the compositor to check whether a delegate-managed fling
  48   // is active or not.
  49   // TODO(hush): Remove after WebView's smooth scrolling path is unified with
  50   // Chrome's.
  51   virtual bool IsExternalScrollActive() const = 0;
  52
  53   // This is called by the compositor when a fling hitting the root layer
  54   // requires a scheduled animation update.
  55   typedef base::Callback<void(base::TimeTicks)> AnimationCallback;
  56   virtual void SetNeedsAnimate(const AnimationCallback& animation) = 0;
  57
  58  protected:
  59   LayerScrollOffsetDelegate() {}
  60   virtual ~LayerScrollOffsetDelegate() {}
  61
  62  private:
  63   DISALLOW_COPY_AND_ASSIGN(LayerScrollOffsetDelegate);
  64 };
  65
  66 }  // namespace cc
  67
  68 #endif  // CC_INPUT_LAYER_SCROLL_OFFSET_DELEGATE_H_