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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 "ui/gfx/animation/slide_animation.h"
      6 
      7 #include <math.h>
      8 
      9 namespace gfx {
     10 
     11 // How many frames per second to target.
     12 static const int kDefaultFrameRateHz = 60;
     13 
     14 // How long animations should take by default.
     15 static const int kDefaultDurationMs = 120;
     16 
     17 SlideAnimation::SlideAnimation(AnimationDelegate* target)
     18     : LinearAnimation(kDefaultFrameRateHz, target),
     19       target_(target),
     20       tween_type_(Tween::EASE_OUT),
     21       showing_(false),
     22       value_start_(0),
     23       value_end_(0),
     24       value_current_(0),
     25       slide_duration_(kDefaultDurationMs) {
     26 }
     27 
     28 SlideAnimation::~SlideAnimation() {
     29 }
     30 
     31 void SlideAnimation::Reset() {
     32   Reset(0);
     33 }
     34 
     35 void SlideAnimation::Reset(double value) {
     36   Stop();
     37   showing_ = static_cast<bool>(value == 1);
     38   value_current_ = value;
     39 }
     40 
     41 void SlideAnimation::Show() {
     42   // If we're already showing (or fully shown), we have nothing to do.
     43   if (showing_)
     44     return;
     45 
     46   showing_ = true;
     47   value_start_ = value_current_;
     48   value_end_ = 1.0;
     49 
     50   // Make sure we actually have something to do.
     51   if (slide_duration_ == 0) {
     52     AnimateToState(1.0);  // Skip to the end of the animation.
     53     return;
     54   } else if (value_current_ == value_end_)  {
     55     return;
     56   }
     57 
     58   // This will also reset the currently-occurring animation.
     59   SetDuration(static_cast<int>(slide_duration_ * (1 - value_current_)));
     60   Start();
     61 }
     62 
     63 void SlideAnimation::Hide() {
     64   // If we're already hiding (or hidden), we have nothing to do.
     65   if (!showing_)
     66     return;
     67 
     68   showing_ = false;
     69   value_start_ = value_current_;
     70   value_end_ = 0.0;
     71 
     72   // Make sure we actually have something to do.
     73   if (slide_duration_ == 0) {
     74     AnimateToState(0.0);  // Skip to the end of the animation.
     75     return;
     76   } else if (value_current_ == value_end_) {
     77     return;
     78   }
     79 
     80   // This will also reset the currently-occurring animation.
     81   SetDuration(static_cast<int>(slide_duration_ * value_current_));
     82   Start();
     83 }
     84 
     85 void SlideAnimation::SetSlideDuration(int duration) {
     86   slide_duration_ = duration;
     87 }
     88 
     89 double SlideAnimation::GetCurrentValue() const {
     90   return value_current_;
     91 }
     92 
     93 void SlideAnimation::AnimateToState(double state) {
     94   if (state > 1.0)
     95     state = 1.0;
     96 
     97   state = Tween::CalculateValue(tween_type_, state);
     98 
     99   value_current_ = value_start_ + (value_end_ - value_start_) * state;
    100 
    101   // Implement snapping.
    102   if (tween_type_ == Tween::EASE_OUT_SNAP &&
    103       fabs(value_current_ - value_end_) <= 0.06)
    104     value_current_ = value_end_;
    105 
    106   // Correct for any overshoot (while state may be capped at 1.0, let's not
    107   // take any rounding error chances.
    108   if ((value_end_ >= value_start_ && value_current_ > value_end_) ||
    109       (value_end_ < value_start_ && value_current_ < value_end_)) {
    110     value_current_ = value_end_;
    111   }
    112 }
    113 
    114 }  // namespace gfx
    115