cc/input/scroll_elasticity_helper.h

   1 // Copyright 2014 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_SCROLL_ELASTICITY_HELPER_H_
   6 #define CC_INPUT_SCROLL_ELASTICITY_HELPER_H_
   7
   8 #include "base/time/time.h"
   9 #include "cc/base/cc_export.h"
  10 #include "ui/gfx/geometry/scroll_offset.h"
  11 #include "ui/gfx/geometry/vector2d_f.h"
  12
  13 namespace cc {
  14
  15 class LayerTreeHostImpl;
  16
  17 // ScrollElasticityHelper is based on
  18 // WebKit/Source/platform/mac/ScrollElasticityController.h
  19 /*
  20  * Copyright (C) 2011 Apple Inc. All rights reserved.
  21  *
  22  * Redistribution and use in source and binary forms, with or without
  23  * modification, are permitted provided that the following conditions
  24  * are met:
  25  * 1. Redistributions of source code must retain the above copyright
  26  *    notice, this list of conditions and the following disclaimer.
  27  * 2. Redistributions in binary form must reproduce the above copyright
  28  *    notice, this list of conditions and the following disclaimer in the
  29  *    documentation and/or other materials provided with the distribution.
  30  *
  31  * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
  32  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  33  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  34  * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
  35  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  36  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  37  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  38  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  39  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  40  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
  41  * THE POSSIBILITY OF SUCH DAMAGE.
  42  */
  43
  44 // Interface between a LayerTreeHostImpl and the ScrollElasticityController. It
  45 // would be possible, in principle, for LayerTreeHostImpl to implement this
  46 // interface itself. This artificial boundary is introduced to reduce the amount
  47 // of logic and state held directly inside LayerTreeHostImpl.
  48 class CC_EXPORT ScrollElasticityHelper {
  49  public:
  50   static ScrollElasticityHelper* CreateForLayerTreeHostImpl(
  51       LayerTreeHostImpl* layer_tree_host_impl);
  52
  53   virtual ~ScrollElasticityHelper() {}
  54
  55   virtual bool IsUserScrollable() const = 0;
  56
  57   // The amount that the view is stretched past the normal allowable bounds.
  58   virtual gfx::Vector2dF StretchAmount() const = 0;
  59   virtual void SetStretchAmount(const gfx::Vector2dF& stretch_amount) = 0;
  60
  61   // Functions for the scrolling of the root scroll layer.
  62   virtual gfx::ScrollOffset ScrollOffset() const = 0;
  63   virtual gfx::ScrollOffset MaxScrollOffset() const = 0;
  64   virtual void ScrollBy(const gfx::Vector2dF& delta) = 0;
  65
  66   // Request that the controller have its Animate method called for the next
  67   // frame.
  68   virtual void RequestAnimate() = 0;
  69 };
  70
  71 }  // namespace cc
  72
  73 #endif  // CC_INPUT_SCROLL_ELASTICITY_HELPER_H_