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.
5 #ifndef CC_INPUT_LAYER_SCROLL_OFFSET_DELEGATE_H_
6 #define CC_INPUT_LAYER_SCROLL_OFFSET_DELEGATE_H_
8 #include "base/basictypes.h"
9 #include "ui/gfx/size_f.h"
10 #include "ui/gfx/vector2d_f.h"
14 // The LayerScrollOffsetDelegate allows for the embedder to take ownership of
15 // the scroll offset of the root layer.
17 // The LayerScrollOffsetDelegate is only used on the impl thread.
18 class LayerScrollOffsetDelegate {
20 // This is called by the compositor to notify the delegate what is the upper
21 // total scroll offset bound.
22 virtual void SetMaxScrollOffset(gfx::Vector2dF max_scroll_offset) = 0;
24 // This is called by the compositor when the scroll offset of the layer would
25 // have otherwise changed.
26 virtual void SetTotalScrollOffset(gfx::Vector2dF new_value) = 0;
28 // This is called by the compositor to query the current scroll offset of the
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;
37 // This is called by the compositor to check whether a delegate-managed fling
39 virtual bool IsExternalFlingActive() const = 0;
41 // This is called by the compositor to notify the delegate what is the current
42 // page scale factor is.
43 virtual void SetTotalPageScaleFactor(float page_scale_factor) = 0;
45 // This is called by the compositor to notify the delegate what is the layer's
46 // scrollable size is.
47 virtual void SetScrollableSize(gfx::SizeF scrollable_size) = 0;
50 LayerScrollOffsetDelegate() {}
51 virtual ~LayerScrollOffsetDelegate() {}
54 DISALLOW_COPY_AND_ASSIGN(LayerScrollOffsetDelegate);
59 #endif // CC_INPUT_LAYER_SCROLL_OFFSET_DELEGATE_H_