cc/animation/scrollbar_animation_controller.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 "cc/animation/scrollbar_animation_controller.h"
   6
   7 #include <algorithm>
   8
   9 #include "base/time/time.h"
  10
  11 namespace cc {
  12
  13 ScrollbarAnimationController::ScrollbarAnimationController(
  14     ScrollbarAnimationControllerClient* client,
  15     base::TimeDelta delay_before_starting,
  16     base::TimeDelta duration)
  17     : client_(client),
  18       delay_before_starting_(delay_before_starting),
  19       duration_(duration),
  20       is_animating_(false),
  21       currently_scrolling_(false),
  22       scroll_gesture_has_scrolled_(false),
  23       weak_factory_(this) {
  24 }
  25
  26 ScrollbarAnimationController::~ScrollbarAnimationController() {
  27 }
  28
  29 void ScrollbarAnimationController::Animate(base::TimeTicks now) {
  30   if (!is_animating_)
  31     return;
  32
  33   if (last_awaken_time_.is_null())
  34     last_awaken_time_ = now;
  35
  36   float progress = AnimationProgressAtTime(now);
  37   RunAnimationFrame(progress);
  38
  39   if (is_animating_) {
  40     delayed_scrollbar_fade_.Cancel();
  41     client_->SetNeedsScrollbarAnimationFrame();
  42   }
  43 }
  44
  45 float ScrollbarAnimationController::AnimationProgressAtTime(
  46     base::TimeTicks now) {
  47   base::TimeDelta delta = now - last_awaken_time_;
  48   float progress = delta.InSecondsF() / duration_.InSecondsF();
  49   return std::max(std::min(progress, 1.f), 0.f);
  50 }
  51
  52 void ScrollbarAnimationController::DidScrollBegin() {
  53   currently_scrolling_ = true;
  54 }
  55
  56 void ScrollbarAnimationController::DidScrollUpdate() {
  57   StopAnimation();
  58   delayed_scrollbar_fade_.Cancel();
  59
  60   // As an optimization, we avoid spamming fade delay tasks during active fast
  61   // scrolls.  But if we're not within one, we need to post every scroll update.
  62   if (!currently_scrolling_)
  63     PostDelayedFade();
  64   else
  65     scroll_gesture_has_scrolled_ = true;
  66 }
  67
  68 void ScrollbarAnimationController::DidScrollEnd() {
  69   if (scroll_gesture_has_scrolled_) {
  70     PostDelayedFade();
  71     scroll_gesture_has_scrolled_ = false;
  72   }
  73
  74   currently_scrolling_ = false;
  75 }
  76
  77 void ScrollbarAnimationController::PostDelayedFade() {
  78   delayed_scrollbar_fade_.Reset(
  79       base::Bind(&ScrollbarAnimationController::StartAnimation,
  80                  weak_factory_.GetWeakPtr()));
  81   client_->PostDelayedScrollbarFade(delayed_scrollbar_fade_.callback(),
  82                                     delay_before_starting_);
  83 }
  84
  85 void ScrollbarAnimationController::StartAnimation() {
  86   delayed_scrollbar_fade_.Cancel();
  87   is_animating_ = true;
  88   last_awaken_time_ = base::TimeTicks();
  89   client_->SetNeedsScrollbarAnimationFrame();
  90 }
  91
  92 void ScrollbarAnimationController::StopAnimation() {
  93   is_animating_ = false;
  94 }
  95
  96 }  // namespace cc