Animations: animate to current time, rather than a set number of frames.

This will cut down on the number of total frames shown for slow animations; should have no effect on fast animations.

This makes the following animations much snappier (as seen on Linux):
- download shelf opening
- bookmark bar opening at large browser width
- new tab animation

BUG=all animation jank bugs
TEST=if you put a Sleep(1000) in an AnimationProgressed callback, you will actually get called back fewer times.
TEST=looked at all the animations I could think of to make sure they still work right.
Review URL: http://codereview.chromium.org/257038

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@27935 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 15 insertions, 21 deletions

diff --git a/app/animation.cc b/app/animation.cc
index 1ef905d..94c99c2 100644
--- a/app/animation.cc
+++ b/app/animation.cc
@@ -10,6 +10,7 @@
 #include "base/win_util.h"
 #endif
 
+using base::Time;
 using base::TimeDelta;
 
 Animation::Animation(int frame_rate,
@@ -17,9 +18,6 @@ Animation::Animation(int frame_rate,
   : animating_(false),
     frame_rate_(frame_rate),
     timer_interval_(CalculateInterval(frame_rate)),
-    duration_(0),
-    iteration_count_(0),
-    current_iteration_(0),
     state_(0.0),
     delegate_(delegate) {
 }
@@ -30,9 +28,7 @@ Animation::Animation(int duration,
   : animating_(false),
     frame_rate_(frame_rate),
     timer_interval_(CalculateInterval(frame_rate)),
-    duration_(0),
-    iteration_count_(0),
-    current_iteration_(0),
+    duration_(TimeDelta::FromMilliseconds(duration)),
     state_(0.0),
     delegate_(delegate) {
 
@@ -43,7 +39,7 @@ Animation::~Animation() {
 }
 
 void Animation::Reset() {
-  current_iteration_ = 0;
+  start_time_ = Time::Now();
 }
 
 double Animation::GetCurrentValue() const {
@@ -53,8 +49,8 @@ double Animation::GetCurrentValue() const {
 
 void Animation::Start() {
   if (!animating_) {
-    timer_.Start(TimeDelta::FromMilliseconds(timer_interval_), this,
-                 &Animation::Run);
+    start_time_ = Time::Now();
+    timer_.Start(timer_interval_, this, &Animation::Run);
 
     animating_ = true;
     if (delegate_)
@@ -92,18 +88,16 @@ bool Animation::IsAnimating() const {
 }
 
 void Animation::SetDuration(int duration) {
-  duration_ = duration;
+  duration_ = TimeDelta::FromMilliseconds(duration);
   if (duration_ < timer_interval_)
     duration_ = timer_interval_;
-  iteration_count_ = duration_ / timer_interval_;
-
-  // Changing the number of iterations forces us to reset the
-  // animation to the first iteration.
-  current_iteration_ = 0;
+  start_time_ = Time::Now();
 }
 
 void Animation::Step() {
-  state_ = static_cast<double>(++current_iteration_) / iteration_count_;
+  TimeDelta elapsed_time = Time::Now() - start_time_;
+  state_ = static_cast<double>(elapsed_time.InMicroseconds()) /
+           static_cast<double>(duration_.InMicroseconds());
 
   if (state_ >= 1.0)
     state_ = 1.0;
@@ -120,11 +114,11 @@ void Animation::Run() {
   Step();
 }
 
-int Animation::CalculateInterval(int frame_rate) {
-  int timer_interval = 1000 / frame_rate;
-  if (timer_interval < 10)
-    timer_interval = 10;
-  return timer_interval;
+TimeDelta Animation::CalculateInterval(int frame_rate) {
+  int timer_interval = 1000000 / frame_rate;
+  if (timer_interval < 10000)
+    timer_interval = 10000;
+  return TimeDelta::FromMicroseconds(timer_interval);
 }
 
 // static