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   // If the pinch zoom anchor on the first PinchUpdate is within this length
  24   // of the screen edge, "snap" the zoom to that edge. Experimentally
  25   // determined.
  26   static const int kPinchZoomSnapMarginDips = 100;
  27
  28   // TODO(tdresser): eventually |consumed_delta| should equal
  29   // |content_scrolled_delta|. See crbug.com/510045 for details.
  30   struct ScrollResult {
  31     gfx::Vector2dF consumed_delta;
  32     gfx::Vector2dF content_scrolled_delta;
  33   };
  34
  35   static scoped_ptr<Viewport> Create(LayerTreeHostImpl* host_impl);
  36
  37   // Differs from scrolling in that only the visual viewport is moved, without
  38   // affecting the top controls or outer viewport.
  39   void Pan(const gfx::Vector2dF& delta);
  40
  41   // Scrolls the viewport, applying the unique bubbling between the inner and
  42   // outer viewport. Scrolls can be consumed by top controls.
  43   ScrollResult ScrollBy(const gfx::Vector2dF& delta,
  44                         const gfx::Point& viewport_point,
  45                         bool is_wheel_scroll,
  46                         bool affect_top_controls);
  47
  48   void PinchUpdate(float magnify_delta, const gfx::Point& anchor);
  49   void PinchEnd();
  50
  51  private:
  52   explicit Viewport(LayerTreeHostImpl* host_impl);
  53
  54   bool ShouldTopControlsConsumeScroll(const gfx::Vector2dF& scroll_delta) const;
  55   gfx::Vector2dF AdjustOverscroll(const gfx::Vector2dF& delta) const;
  56
  57   // Sends the delta to the top controls, returns the amount applied.
  58   gfx::Vector2dF ScrollTopControls(const gfx::Vector2dF& delta);
  59
  60   gfx::ScrollOffset MaxTotalScrollOffset() const;
  61   gfx::ScrollOffset TotalScrollOffset() const;
  62
  63   LayerImpl* InnerScrollLayer() const;
  64   LayerImpl* OuterScrollLayer() const;
  65
  66   void SnapPinchAnchorIfWithinMargin(const gfx::Point& anchor);
  67
  68   LayerTreeHostImpl* host_impl_;
  69
  70   bool pinch_zoom_active_;
  71
  72   // The pinch zoom anchor point is adjusted by this amount during a pinch. This
  73   // is used to "snap" a pinch-zoom to the edge of the screen.
  74   gfx::Vector2d pinch_anchor_adjustment_;
  75
  76   DISALLOW_COPY_AND_ASSIGN(Viewport);
  77 };
  78
  79 }  // namespace cc
  80
  81 #endif  // CC_LAYERS_VIEWPORT_H_