Implement 3-stage minimize animation for Panels on OSX.

chrome/browser/ui/panels/panel_window_controller_cocoa.mm

Index: chrome/browser/ui/panels/panel_window_controller_cocoa.mm
diff --git a/chrome/browser/ui/panels/panel_window_controller_cocoa.mm b/chrome/browser/ui/panels/panel_window_controller_cocoa.mm
index 06e69df40e587410dc730d05bad69c18ca377ad3..797573a46a34f9cc8023a7cdb040b4d0e08104e6 100644
--- a/chrome/browser/ui/panels/panel_window_controller_cocoa.mm
+++ b/chrome/browser/ui/panels/panel_window_controller_cocoa.mm
@@ -428,20 +428,19 @@ enum {
   // Will be enabled back in animationDidEnd callback.
   [self disableTabContentsViewAutosizing];
 
+  // Terminate previous animation, if it is still playing.
+  [self terminateBoundsAnimation];
+
   NSDictionary *windowResize = [NSDictionary dictionaryWithObjectsAndKeys:
       [self window], NSViewAnimationTargetKey,
       [NSValue valueWithRect:frame], NSViewAnimationEndFrameKey, nil];
 
   NSArray *animations = [NSArray arrayWithObjects:windowResize, nil];
 
-  // Terminate previous animation, if it is still playing.
-  [self terminateBoundsAnimation];
   boundsAnimation_ =
       [[NSViewAnimation alloc] initWithViewAnimations:animations];
   [boundsAnimation_ setDelegate:self];
 
-  [boundsAnimation_ setAnimationBlockingMode: NSAnimationNonblocking];
-
   NSRect currentFrame = [[self window] frame];
   // Compute duration. We use constant speed of animation, however if the change
   // is too large, we clip the duration (effectively increasing speed) to
@@ -454,11 +453,55 @@ enum {
   double distance = std::max(distanceX, distanceY);
   double duration = std::min(distance / kBoundsAnimationSpeedPixelsPerSecond,
                              kBoundsAnimationMaxDurationSeconds);
+  // Detect animation that happens when expansion state is set to MINIMIZED
+  // and there is relatively big portion of the panel to hide from view.
+  // Initialize animation differently in this case, using fast-pause-slow
+  // method, see below for more details.
+  if (windowShim_->panel()->expansion_state() == Panel::MINIMIZED) {
+    float titlebarToFrameProportion =
+        (windowShim_->TitleOnlyHeight() - NSHeight(frame)) / distanceY;

[jianli, 2011/12/02 06:18:32]

Is NSHeight(frame) for the height of the expanded panel? If so,
titlebarToFrameProportion seens to be a negative value.

[Dmitry Titov, 2011/12/02 06:47:10]

The |frame| here is a new frame, since we are minimizing it's 4-px one. The
|currentFrame| is the previous one.

I need to subtract the new frame to obtain exact ratio when stopped animation
would only show the titlebar. Updated name of variable in hope to be more
descriptive.

+    if (titlebarToFrameProportion < 0.3) {  // Relatively big movement.
+      playingMinimizeAnimation_ = YES;
+      animationSpeedThreshold_ = 1.0 - titlebarToFrameProportion;
+      duration = 1.5;
+    }
+  }
   [boundsAnimation_ setDuration: duration];
+  [boundsAnimation_ setFrameRate:0.0];
+  [boundsAnimation_ setAnimationBlockingMode: NSAnimationNonblocking];
   [boundsAnimation_ startAnimation];
 }
 
+- (float)animation:(NSAnimation*)animation
+  valueForProgress:(NSAnimationProgress)progress {
+  if (!playingMinimizeAnimation_) {
+    // Cubic easing out.
+    float value = 1.0 - progress;
+    return 1.0 - value * value * value;
+  }
+
+  // Minimize animation:
+  // 1. Quickly (0 -> 0.15) make only titlebar visible.
+  // 2. Stay a little bit (0.15->0.6) in place, just showing titlebar.
+  // 3. Slowly minimize to thin strip (0.6->1.0)
+  const float kAnimationStopAfterQuickDecrease = 0.15;
+  const float kAnimationStopAfterShowingTitlebar = 0.6;
+  float value;
+  if (progress <= kAnimationStopAfterQuickDecrease)

[jianli, 2011/12/02 06:18:32]

nit: better to add brackets.

[Dmitry Titov, 2011/12/02 06:47:10]

Done.

+    value =
+        progress * animationSpeedThreshold_ / kAnimationStopAfterQuickDecrease;
+  else if (progress <= kAnimationStopAfterShowingTitlebar)
+    value = animationSpeedThreshold_;
+  else
+    value = animationSpeedThreshold_ +
+        (progress - kAnimationStopAfterShowingTitlebar) *
+        (1.0 - animationSpeedThreshold_) /
+        (1.0 - kAnimationStopAfterShowingTitlebar);
+  return value;
+}
+
 - (void)animationDidEnd:(NSAnimation*)animation {
+  playingMinimizeAnimation_ = NO;
   if (windowShim_->panel()->expansion_state() == Panel::EXPANDED)
     [self enableTabContentsViewAutosizing];