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// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef CC_INPUT_LAYER_SCROLL_OFFSET_DELEGATE_H_
#define CC_INPUT_LAYER_SCROLL_OFFSET_DELEGATE_H_
#include "base/basictypes.h"
#include "ui/gfx/size_f.h"
#include "ui/gfx/vector2d_f.h"
namespace cc {
// The LayerScrollOffsetDelegate allows for the embedder to take ownership of
// the scroll offset of the root layer.
//
// The LayerScrollOffsetDelegate is only used on the impl thread.
class LayerScrollOffsetDelegate {
public:
// This is called by the compositor to query the current scroll offset of the
// layer.
// There is no requirement that the return values of this method are
// stable in time (two subsequent calls may yield different results).
// The return value is not required to be related to the values passed in to
// the SetTotalScrollOffset method in any way however it is required to be no
// more than the value passed to the most recent SetMaxScrollOffset call.
virtual gfx::Vector2dF GetTotalScrollOffset() = 0;
// This is called by the compositor to notify the delegate of any change to
// the following parameters:
// |total_scroll_offset| current scroll offset of the root layer,
// |max_scroll_offset| total scroll offset upper bound for the root layer,
// |scrollable_size| root layer scrollable size,
// |page_scale_factor| current page scale,
// |min_page_scale_factor| page scale lower limit,
// |max_page_scale_factor| page scale upper limit.
virtual void UpdateRootLayerState(const gfx::Vector2dF& total_scroll_offset,
const gfx::Vector2dF& max_scroll_offset,
const gfx::SizeF& scrollable_size,
float page_scale_factor,
float min_page_scale_factor,
float max_page_scale_factor) = 0;
// This is called by the compositor to check whether a delegate-managed fling
// is active or not.
virtual bool IsExternalFlingActive() const = 0;
protected:
LayerScrollOffsetDelegate() {}
virtual ~LayerScrollOffsetDelegate() {}
private:
DISALLOW_COPY_AND_ASSIGN(LayerScrollOffsetDelegate);
};
} // namespace cc
#endif // CC_INPUT_LAYER_SCROLL_OFFSET_DELEGATE_H_
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