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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 #include "webkit/child/fling_animator_impl_android.h"
      6 
      7 #include "base/android/jni_android.h"
      8 #include "base/android/scoped_java_ref.h"
      9 #include "base/logging.h"
     10 #include "jni/OverScroller_jni.h"
     11 #include "third_party/WebKit/public/platform/WebFloatSize.h"
     12 #include "third_party/WebKit/public/platform/WebGestureCurveTarget.h"
     13 #include "ui/gfx/screen.h"
     14 #include "ui/gfx/vector2d.h"
     15 
     16 namespace webkit_glue {
     17 
     18 namespace {
     19 static const float kEpsilon = 1e-4;
     20 }
     21 
     22 FlingAnimatorImpl::FlingAnimatorImpl()
     23     : is_active_(false) {
     24   // hold the global reference of the Java objects.
     25   JNIEnv* env = base::android::AttachCurrentThread();
     26   java_scroller_.Reset(JNI_OverScroller::Java_OverScroller_ConstructorAWOS_ACC(
     27       env,
     28       base::android::GetApplicationContext()));
     29 }
     30 
     31 FlingAnimatorImpl::~FlingAnimatorImpl()
     32 {
     33 }
     34 
     35 //static
     36 bool FlingAnimatorImpl::RegisterJni(JNIEnv* env) {
     37   return JNI_OverScroller::RegisterNativesImpl(env);
     38 }
     39 
     40 void FlingAnimatorImpl::StartFling(const gfx::PointF& velocity)
     41 {
     42   // No bounds on the fling. See http://webkit.org/b/96403
     43   // Instead, use the largest possible bounds for minX/maxX/minY/maxY. The
     44   // compositor will ignore any attempt to scroll beyond the end of the page.
     45 
     46   DCHECK(velocity.x() || velocity.y());
     47   if (is_active_)
     48     CancelFling();
     49 
     50   is_active_ = true;
     51   last_time_ = 0;
     52   last_velocity_ = velocity;
     53 
     54   JNIEnv* env = base::android::AttachCurrentThread();
     55 
     56   JNI_OverScroller::Java_OverScroller_flingV_I_I_I_I_I_I_I_I(
     57       env, java_scroller_.obj(), 0, 0,
     58       static_cast<int>(velocity.x()),
     59       static_cast<int>(velocity.y()),
     60       INT_MIN, INT_MAX, INT_MIN, INT_MAX);
     61 }
     62 
     63 void FlingAnimatorImpl::CancelFling()
     64 {
     65   if (!is_active_)
     66     return;
     67 
     68   is_active_ = false;
     69   JNIEnv* env = base::android::AttachCurrentThread();
     70   JNI_OverScroller::Java_OverScroller_abortAnimation(env, java_scroller_.obj());
     71 }
     72 
     73 bool FlingAnimatorImpl::UpdatePosition()
     74 {
     75   JNIEnv* env = base::android::AttachCurrentThread();
     76   bool result = JNI_OverScroller::Java_OverScroller_computeScrollOffset(
     77       env,
     78       java_scroller_.obj());
     79   return is_active_ = result;
     80 }
     81 
     82 gfx::Point FlingAnimatorImpl::GetCurrentPosition()
     83 {
     84   JNIEnv* env = base::android::AttachCurrentThread();
     85   gfx::Point position(
     86       JNI_OverScroller::Java_OverScroller_getCurrX(env, java_scroller_.obj()),
     87       JNI_OverScroller::Java_OverScroller_getCurrY(env, java_scroller_.obj()));
     88   return position;
     89 }
     90 
     91 float FlingAnimatorImpl::GetCurrentVelocity()
     92 {
     93   JNIEnv* env = base::android::AttachCurrentThread();
     94   // TODO(jdduke): Add Java-side hooks for getCurrVelocityX/Y, and return
     95   //               vector velocity.
     96   return JNI_OverScroller::Java_OverScroller_getCurrVelocity(
     97       env, java_scroller_.obj());
     98 }
     99 
    100 bool FlingAnimatorImpl::apply(double time,
    101                               blink::WebGestureCurveTarget* target) {
    102   if (!UpdatePosition())
    103     return false;
    104 
    105   gfx::Point current_position = GetCurrentPosition();
    106   gfx::Vector2d diff(current_position - last_position_);
    107   last_position_ = current_position;
    108   float dpi_scale = gfx::Screen::GetNativeScreen()->GetPrimaryDisplay()
    109       .device_scale_factor();
    110   blink::WebFloatSize scroll_amount(diff.x() / dpi_scale,
    111                                      diff.y() / dpi_scale);
    112 
    113   float delta_time = time - last_time_;
    114   last_time_ = time;
    115 
    116   // Currently, the OverScroller only provides the velocity magnitude; use the
    117   // angle of the scroll delta to yield approximate x and y velocity components.
    118   // TODO(jdduke): Remove this when we can properly poll OverScroller velocity.
    119   gfx::PointF current_velocity = last_velocity_;
    120   if (delta_time > kEpsilon) {
    121     float diff_length = diff.Length();
    122     if (diff_length > kEpsilon) {
    123       float velocity = GetCurrentVelocity();
    124       float scroll_to_velocity = velocity / diff_length;
    125       current_velocity = gfx::PointF(diff.x() * scroll_to_velocity,
    126                                      diff.y() * scroll_to_velocity);
    127     }
    128   }
    129   last_velocity_ = current_velocity;
    130   blink::WebFloatSize fling_velocity(current_velocity.x() / dpi_scale,
    131                                       current_velocity.y() / dpi_scale);
    132   target->notifyCurrentFlingVelocity(fling_velocity);
    133 
    134   // scrollBy() could delete this curve if the animation is over, so don't touch
    135   // any member variables after making that call.
    136   target->scrollBy(scroll_amount);
    137   return true;
    138 }
    139 
    140 FlingAnimatorImpl* FlingAnimatorImpl::CreateAndroidGestureCurve(
    141     const blink::WebFloatPoint& velocity,
    142     const blink::WebSize&) {
    143   FlingAnimatorImpl* gesture_curve = new FlingAnimatorImpl();
    144   gesture_curve->StartFling(velocity);
    145   return gesture_curve;
    146 }
    147 
    148 } // namespace webkit_glue
    149