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      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 #include "content/child/fling_animator_impl_android.h"
      6 
      7 #include "base/logging.h"
      8 #include "third_party/WebKit/public/platform/WebFloatSize.h"
      9 #include "third_party/WebKit/public/platform/WebGestureCurveTarget.h"
     10 #include "ui/gfx/frame_time.h"
     11 #include "ui/gfx/vector2d.h"
     12 
     13 namespace content {
     14 
     15 namespace {
     16 
     17 // Value taken directly from Android's ViewConfiguration. As the value has not
     18 // changed in 4+ years, and does not depend on any device-specific configuration
     19 // parameters, copy it directly to avoid potential JNI interop issues in the
     20 // render process (see crbug.com/362614).
     21 const float kDefaultAndroidPlatformScrollFriction = 0.015f;
     22 
     23 gfx::Scroller::Config GetScrollerConfig() {
     24   gfx::Scroller::Config config;
     25   config.flywheel_enabled = false;
     26   config.fling_friction = kDefaultAndroidPlatformScrollFriction;
     27   return config;
     28 }
     29 
     30 }  // namespace
     31 
     32 FlingAnimatorImpl::FlingAnimatorImpl()
     33     : is_active_(false),
     34       scroller_(GetScrollerConfig()) {}
     35 
     36 FlingAnimatorImpl::~FlingAnimatorImpl() {}
     37 
     38 void FlingAnimatorImpl::StartFling(const gfx::PointF& velocity) {
     39   // No bounds on the fling. See http://webkit.org/b/96403
     40   // Instead, use the largest possible bounds for minX/maxX/minY/maxY. The
     41   // compositor will ignore any attempt to scroll beyond the end of the page.
     42 
     43   DCHECK(velocity.x() || velocity.y());
     44   if (is_active_)
     45     CancelFling();
     46 
     47   is_active_ = true;
     48   scroller_.Fling(0,
     49                   0,
     50                   velocity.x(),
     51                   velocity.y(),
     52                   INT_MIN,
     53                   INT_MAX,
     54                   INT_MIN,
     55                   INT_MAX,
     56                   base::TimeTicks());
     57 }
     58 
     59 void FlingAnimatorImpl::CancelFling() {
     60   if (!is_active_)
     61     return;
     62 
     63   is_active_ = false;
     64   scroller_.AbortAnimation();
     65 }
     66 
     67 bool FlingAnimatorImpl::apply(double time,
     68                               blink::WebGestureCurveTarget* target) {
     69   // If the fling has yet to start, simply return and report true to prevent
     70   // fling termination.
     71   if (time <= 0)
     72     return true;
     73 
     74   const base::TimeTicks time_ticks =
     75       base::TimeTicks() + base::TimeDelta::FromMicroseconds(
     76                               time * base::Time::kMicrosecondsPerSecond);
     77   if (!scroller_.ComputeScrollOffset(time_ticks)) {
     78     is_active_ = false;
     79     return false;
     80   }
     81 
     82   gfx::PointF current_position(scroller_.GetCurrX(), scroller_.GetCurrY());
     83   gfx::Vector2dF scroll_amount(current_position - last_position_);
     84   last_position_ = current_position;
     85 
     86   // scrollBy() could delete this curve if the animation is over, so don't touch
     87   // any member variables after making that call.
     88   return target->scrollBy(blink::WebFloatSize(scroll_amount),
     89                           blink::WebFloatSize(scroller_.GetCurrVelocityX(),
     90                                               scroller_.GetCurrVelocityY()));
     91 }
     92 
     93 FlingAnimatorImpl* FlingAnimatorImpl::CreateAndroidGestureCurve(
     94     const blink::WebFloatPoint& velocity,
     95     const blink::WebSize&) {
     96   FlingAnimatorImpl* gesture_curve = new FlingAnimatorImpl();
     97   gesture_curve->StartFling(velocity);
     98   return gesture_curve;
     99 }
    100 
    101 }  // namespace content
    102