content/child/fling_animator_impl_android.cc

   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