Add 3-stage animation for minimization of Panels on Win.

chrome/browser/ui/panels/panel_browser_view.cc

Index: chrome/browser/ui/panels/panel_browser_view.cc
diff --git a/chrome/browser/ui/panels/panel_browser_view.cc b/chrome/browser/ui/panels/panel_browser_view.cc
index 6bb2108a3708f11034744c4bdcf958eca1b87cb8..7e676c49ecb5bd3c736adfe88dfaeb0ab038cea1 100644
--- a/chrome/browser/ui/panels/panel_browser_view.cc
+++ b/chrome/browser/ui/panels/panel_browser_view.cc
@@ -17,7 +17,6 @@
 #include "chrome/common/chrome_switches.h"
 #include "content/public/browser/notification_service.h"
 #include "grit/chromium_strings.h"
-#include "ui/base/animation/slide_animation.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/views/controls/label.h"
 #include "ui/views/widget/widget.h"
@@ -25,6 +24,7 @@
 namespace {
 // This value is experimental and subjective.
 const int kSetBoundsAnimationMs = 180;
+const int kSetBoundsAnimationMinimizeMs = 1500;
 
 // The threshold to differentiate the short click and long click.
 const int kShortClickThresholdMs = 200;
@@ -35,6 +35,35 @@ const int kSuspendMinimizeOnClickIntervalMs = 500;
 
 }
 
+double PanelSlideAnimation::GetCurrentValue() const {
+  double progress = ui::SlideAnimation::GetCurrentValue();
+  if (!for_minimize_) {
+    // 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 double kAnimationStopAfterQuickDecrease = 0.15;
+  const double kAnimationStopAfterShowingTitlebar = 0.6;
+  double value;
+  if (progress <= kAnimationStopAfterQuickDecrease) {
+      value = progress * animation_stop_to_show_titlebar_ /
+          kAnimationStopAfterQuickDecrease;
+  } else if (progress <= kAnimationStopAfterShowingTitlebar) {
+      value = animation_stop_to_show_titlebar_;
+  } else {
+      value = animation_stop_to_show_titlebar_ +
+          (progress - kAnimationStopAfterShowingTitlebar) *
+          (1.0 - animation_stop_to_show_titlebar_) /
+          (1.0 - kAnimationStopAfterShowingTitlebar);
+  }
+  return value;
+}
+
 NativePanel* Panel::CreateNativePanel(Browser* browser, Panel* panel,
                                       const gfx::Rect& bounds) {
   PanelBrowserView* view = new PanelBrowserView(browser, panel, bounds);
@@ -140,13 +169,26 @@ void PanelBrowserView::SetBoundsInternal(const gfx::Rect& new_bounds,
 
   animation_start_bounds_ = GetBounds();
 
-  if (!bounds_animator_.get()) {
-    bounds_animator_.reset(new ui::SlideAnimation(this));
-    bounds_animator_->SetSlideDuration(kSetBoundsAnimationMs);
+  // 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.
+  double animation_stop_to_show_titlebar = 0;
+  bool for_minimize = false;
+  int duration = kSetBoundsAnimationMs;
+  if (panel_->expansion_state() == Panel::MINIMIZED) {
+    animation_stop_to_show_titlebar =
+        1.0 - static_cast<double>((TitleOnlyHeight() - new_bounds.height())) /
+        (GetBounds().height() - new_bounds.height());
+    if (animation_stop_to_show_titlebar > 0.7) {  // Relatively big movement.
+      for_minimize = true;
+      duration = kSetBoundsAnimationMinimizeMs;
+    }
   }
 
-  if (bounds_animator_->IsShowing())
-    bounds_animator_->Reset();
+  bounds_animator_.reset(new PanelSlideAnimation(
+      this, for_minimize, animation_stop_to_show_titlebar));
+  bounds_animator_->SetSlideDuration(duration);
   bounds_animator_->Show();
 }