Tweaks the pinned background tab title change animation per Nicholas's

request.

BUG=none
TEST=none

Review URL: http://codereview.chromium.org/3041006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@52949 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 47 insertions, 5 deletions

diff --git a/app/multi_animation.cc b/app/multi_animation.cc
index 703ed85..14cd7f9 100644
--- a/app/multi_animation.cc
+++ b/app/multi_animation.cc
@@ -9,8 +9,10 @@ static const int kDefaultInterval = 20;
 
 static int TotalTime(const MultiAnimation::Parts& parts) {
   int time_ms = 0;
-  for (size_t i = 0; i < parts.size(); ++i)
+  for (size_t i = 0; i < parts.size(); ++i) {
+    DCHECK(parts[i].end_time_ms - parts[i].start_time_ms >= parts[i].time_ms);
     time_ms += parts[i].time_ms;
+  }
   return time_ms;
 }
 
@@ -30,8 +32,9 @@ void MultiAnimation::Step(base::TimeTicks time_now) {
   int delta = static_cast<int>((time_now - start_time()).InMilliseconds() %
                                cycle_time_ms_);
   const Part& part = GetPart(&delta, &current_part_index_);
-  double percent = static_cast<double>(delta) /
-        static_cast<double>(part.time_ms);
+  double percent = static_cast<double>(delta + part.start_time_ms) /
+        static_cast<double>(part.end_time_ms);
+  DCHECK(percent <= 1);
   current_value_ = Tween::CalculateValue(part.type, percent);
 
   if ((current_value_ != last_value || current_part_index_ != last_index) &&
diff --git a/app/multi_animation.h b/app/multi_animation.h
index ac0ab84..7c9ca6d 100644
--- a/app/multi_animation.h
+++ b/app/multi_animation.h
@@ -16,11 +16,28 @@
 // invoked.
 class MultiAnimation : public Animation {
  public:
+  // Defines part of the animation. Each part consists of the following:
+  //
+  // time_ms: the time of the part.
+  // start_time_ms: the amount of time to offset this part by when calculating
+  // the percented completed.
+  // end_time_ms: the end time used to calculate the percentange completed.
+  //
+  // In most cases |start_time_ms| = 0 and |end_time_ms| = |time_ms|. But you
+  // can adjust the start/end for different effects. For example, to run a part
+  // for 200ms with a % between .25 and .75 use the following three values: 200,
+  // 100, 400.
   struct Part {
-    Part() : time_ms(0), type(Tween::ZERO) {}
-    Part(int time_ms, Tween::Type type) : time_ms(time_ms), type(type) {}
+    Part() : time_ms(0), start_time_ms(0), end_time_ms(0), type(Tween::ZERO) {}
+    Part(int time_ms, Tween::Type type)
+        : time_ms(time_ms),
+          start_time_ms(0),
+          end_time_ms(time_ms),
+          type(type) {}
 
     int time_ms;
+    int start_time_ms;
+    int end_time_ms;
     Tween::Type type;
   };
 
diff --git a/app/multi_animation_unittest.cc b/app/multi_animation_unittest.cc
index c3990591..fbbf1b0 100644
--- a/app/multi_animation_unittest.cc
+++ b/app/multi_animation_unittest.cc
@@ -34,3 +34,25 @@ TEST_F(MultiAnimationTest, Basic) {
   EXPECT_EQ(Tween::CalculateValue(Tween::EASE_OUT, .2),
             animation.GetCurrentValue());
 }
+
+TEST_F(MultiAnimationTest, DifferingStartAndEnd) {
+  // Create a MultiAnimation with two parts.
+  MultiAnimation::Parts parts;
+  parts.push_back(MultiAnimation::Part(200, Tween::LINEAR));
+  parts[0].start_time_ms = 100;
+  parts[0].end_time_ms = 400;
+
+  MultiAnimation animation(parts);
+  AnimationContainer::Element* as_element =
+      static_cast<AnimationContainer::Element*>(&animation);
+  as_element->SetStartTime(base::TimeTicks());
+
+  // Step to 0. Because the start_time is 100, this should be 100ms into the
+  // animation
+  as_element->Step(base::TimeTicks());
+  EXPECT_EQ(.25, animation.GetCurrentValue());
+
+  // Step to 100, which is effectively 200ms into the animation.
+  as_element->Step(base::TimeTicks() + base::TimeDelta::FromMilliseconds(100));
+  EXPECT_EQ(.5, animation.GetCurrentValue());
+}