cc/layers/viewport.h

   1 // Copyright 2015 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_LAYERS_VIEWPORT_H_
   6 #define CC_LAYERS_VIEWPORT_H_
   7
   8 #include "base/memory/scoped_ptr.h"
   9 #include "cc/layers/layer_impl.h"
  10 #include "ui/gfx/geometry/vector2d_f.h"
  11
  12 namespace cc {
  13
  14 class LayerTreeHostImpl;
  15
  16 // Encapsulates gesture handling logic on the viewport layers. The "viewport"
  17 // is made up of two scrolling layers, the inner viewport (visual) and the
  18 // outer viewport (layout) scroll layers. These layers have different scroll
  19 // bubbling behavior from the rest of the layer tree which is encoded in this
  20 // class.
  21 class CC_EXPORT Viewport {
  22  public:
  23   struct ScrollResult {
  24     gfx::Vector2dF applied_delta;
  25     gfx::Vector2dF unused_scroll_delta;
  26     gfx::Vector2dF top_controls_applied_delta;
  27   };
  28
  29   static scoped_ptr<Viewport> Create(LayerTreeHostImpl* host_impl);
  30
  31   // Differs from scrolling in that only the visual viewport is moved, without
  32   // affecting the top controls or outer viewport.
  33   void Pan(const gfx::Vector2dF& delta);
  34
  35   // Scrolls the viewport, applying the unique bubbling between the inner and
  36   // outer viewport. Scrolls can be consumed by top controls.
  37   ScrollResult ScrollBy(const gfx::Vector2dF& delta,
  38                         const gfx::Point& viewport_point,
  39                         bool is_wheel_scroll,
  40                         bool affect_top_controls);
  41
  42  private:
  43   explicit Viewport(LayerTreeHostImpl* host_impl);
  44
  45   bool ShouldTopControlsConsumeScroll(const gfx::Vector2dF& scroll_delta) const;
  46   gfx::Vector2dF AdjustOverscroll(const gfx::Vector2dF& delta) const;
  47
  48   // Sends the delta to the top controls, returns the amount applied.
  49   gfx::Vector2dF ScrollTopControls(const gfx::Vector2dF& delta);
  50
  51   gfx::ScrollOffset MaxTotalScrollOffset() const;
  52   gfx::ScrollOffset TotalScrollOffset() const;
  53
  54   LayerImpl* InnerScrollLayer() const;
  55   LayerImpl* OuterScrollLayer() const;
  56
  57   LayerTreeHostImpl* host_impl_;
  58
  59   DISALLOW_COPY_AND_ASSIGN(Viewport);
  60 };
  61
  62 }  // namespace cc
  63
  64 #endif  // CC_LAYERS_VIEWPORT_H_