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      1 // Copyright (c) 2012 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 CONTENT_BROWSER_ANDROID_OVERSCROLL_GLOW_H_
      6 #define CONTENT_BROWSER_ANDROID_OVERSCROLL_GLOW_H_
      7 
      8 #include "base/callback.h"
      9 #include "base/memory/ref_counted.h"
     10 #include "base/memory/scoped_ptr.h"
     11 #include "base/time/time.h"
     12 #include "ui/gfx/size_f.h"
     13 #include "ui/gfx/vector2d_f.h"
     14 
     15 namespace cc {
     16 class Layer;
     17 }
     18 
     19 namespace content {
     20 
     21 class EdgeEffectBase;
     22 
     23 /* |OverscrollGlow| mirrors its Android counterpart, OverscrollGlow.java.
     24  * Conscious tradeoffs were made to align this as closely as possible with the
     25  * original Android Java version.
     26  */
     27 class OverscrollGlow {
     28  public:
     29   enum Edge { EDGE_TOP = 0, EDGE_LEFT, EDGE_BOTTOM, EDGE_RIGHT, EDGE_COUNT };
     30 
     31   // Allows lazy creation of the edge effects.
     32   typedef base::Callback<scoped_ptr<EdgeEffectBase>(void)> EdgeEffectProvider;
     33 
     34   // |edge_effect_provider| must be valid for the duration of the effect's
     35   // lifetime.  The effect is enabled by default, but will remain dormant until
     36   // the first overscroll event.
     37   explicit OverscrollGlow(const EdgeEffectProvider& edge_effect_provider);
     38 
     39   ~OverscrollGlow();
     40 
     41   // Enable the effect. If the effect was previously disabled, it will remain
     42   // dormant until subsequent calls to |OnOverscrolled()|.
     43   void Enable();
     44 
     45   // Deactivate and detach the effect. Subsequent calls to |OnOverscrolled()| or
     46   // |Animate()| will have no effect.
     47   void Disable();
     48 
     49   // Effect layers will be attached to |overscrolling_layer| if necessary.
     50   // |accumulated_overscroll| and |overscroll_delta| are in device pixels, while
     51   // |velocity| is in device pixels / second.
     52   // Returns true if the effect still needs animation ticks.
     53   bool OnOverscrolled(cc::Layer* overscrolling_layer,
     54                       base::TimeTicks current_time,
     55                       gfx::Vector2dF accumulated_overscroll,
     56                       gfx::Vector2dF overscroll_delta,
     57                       gfx::Vector2dF velocity,
     58                       gfx::Vector2dF overscroll_location);
     59 
     60   // Returns true if the effect still needs animation ticks.
     61   // Note: The effect will detach itself when no further animation is required.
     62   bool Animate(base::TimeTicks current_time);
     63 
     64   // Update the effect according to the most recent display parameters,
     65   // Note: All dimensions are in device pixels.
     66   struct DisplayParameters {
     67     DisplayParameters();
     68     gfx::SizeF size;
     69     float edge_offsets[EDGE_COUNT];
     70   };
     71   void UpdateDisplayParameters(const DisplayParameters& params);
     72 
     73  private:
     74   enum Axis { AXIS_X, AXIS_Y };
     75 
     76   // Returns whether the effect is initialized.
     77   bool InitializeIfNecessary();
     78   bool NeedsAnimate() const;
     79   void UpdateLayerAttachment(cc::Layer* parent);
     80   void Detach();
     81   void Pull(base::TimeTicks current_time,
     82             const gfx::Vector2dF& overscroll_delta,
     83             const gfx::Vector2dF& overscroll_location);
     84   void Absorb(base::TimeTicks current_time,
     85               const gfx::Vector2dF& velocity,
     86               bool x_overscroll_started,
     87               bool y_overscroll_started);
     88   void Release(base::TimeTicks current_time);
     89 
     90   EdgeEffectBase* GetOppositeEdge(int edge_index);
     91 
     92   EdgeEffectProvider edge_effect_provider_;
     93   scoped_ptr<EdgeEffectBase> edge_effects_[EDGE_COUNT];
     94 
     95   DisplayParameters display_params_;
     96   bool enabled_;
     97   bool initialized_;
     98 
     99   scoped_refptr<cc::Layer> root_layer_;
    100 
    101   DISALLOW_COPY_AND_ASSIGN(OverscrollGlow);
    102 };
    103 
    104 }  // namespace content
    105 
    106 #endif  // CONTENT_BROWSER_ANDROID_SCROLL_GLOW_H_
    107