Add bounce to tray icon preview drop animation

BUG=1142572

Change-Id: Iefc890de450ed2037e5755441f116df4aaeb01e5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2577726Reviewed-by: Robert Flack <flackr@chromium.org>
Reviewed-by: David Black <dmblack@google.com>
Commit-Queue: Toni Baržić <tbarzic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#834876}

ash/system/holding_space/holding_space_tray_icon_preview.cc

@@ -13,6 +13,7 @@
 #include "ash/system/tray/tray_constants.h"
 #include "base/i18n/rtl.h"
 #include "ui/compositor/layer.h"
+#include "ui/compositor/layer_animation_sequence.h"
 #include "ui/compositor/paint_recorder.h"
 #include "ui/compositor/scoped_layer_animation_settings.h"
 #include "ui/gfx/canvas.h"
@@ -29,6 +30,15 @@ namespace {
 // Appearance.
 constexpr int kElevation = 2;
 
+// The duration of each of the preview icon bounce animation.
+constexpr base::TimeDelta kBounceAnimationSegmentDuration =
+    base::TimeDelta::FromMilliseconds(250);
+
+// The delay with which preview icon is dropped into the holding space tray
+// icon.
+constexpr base::TimeDelta kBounceAnimationBaseDelay =
+    base::TimeDelta::FromMilliseconds(150);
+
 // Helpers ---------------------------------------------------------------------
 
 // Returns the shadow details to use when painting elevation.
@@ -191,10 +201,31 @@ void HoldingSpaceTrayIconPreview::AnimateIn(size_t index) {
     parent->StackBelow(layer_.get(), children[children.size() - index - 1]);
   }
 
-  ui::ScopedLayerAnimationSettings animation_settings(layer_->GetAnimator());
-  SetUpAnimation(&animation_settings);
+  gfx::Transform mid_transform(transform_);
+  mid_transform.Translate(0, kTrayItemSize * 0.25f);
 
-  layer_->SetTransform(transform_);
+  ui::ScopedLayerAnimationSettings scoped_settings(layer_->GetAnimator());
+  scoped_settings.SetPreemptionStrategy(
+      ui::LayerAnimator::IMMEDIATELY_ANIMATE_TO_NEW_TARGET);
+
+  std::unique_ptr<ui::LayerAnimationSequence> sequence =
+      std::make_unique<ui::LayerAnimationSequence>();
+  sequence->AddElement(ui::LayerAnimationElement::CreatePauseElement(
+      ui::LayerAnimationElement::TRANSFORM, kBounceAnimationBaseDelay));
+
+  std::unique_ptr<ui::LayerAnimationElement> initial_drop =
+      ui::LayerAnimationElement::CreateTransformElement(
+          mid_transform, kBounceAnimationSegmentDuration);
+  initial_drop->set_tween_type(gfx::Tween::EASE_OUT_4);
+  sequence->AddElement(std::move(initial_drop));
+
+  std::unique_ptr<ui::LayerAnimationElement> rebound =
+      ui::LayerAnimationElement::CreateTransformElement(
+          transform_, kBounceAnimationSegmentDuration);
+  rebound->set_tween_type(gfx::Tween::FAST_OUT_SLOW_IN_3);
+  sequence->AddElement(std::move(rebound));
+
+  layer_->GetAnimator()->StartAnimation(sequence.release());
 }
 
 void HoldingSpaceTrayIconPreview::AnimateOut(

ui/gfx/animation/tween.cc

@@ -45,6 +45,9 @@ double Tween::CalculateValue(Tween::Type type, double state) {
     case EASE_OUT_3:
       return gfx::CubicBezier(0.6, 0, 0, 1).Solve(state);
 
+    case EASE_OUT_4:
+      return gfx::CubicBezier(1, 0, 0.8, 1).Solve(state);
+
     case LINEAR:
       return state;
 
@@ -63,6 +66,9 @@ double Tween::CalculateValue(Tween::Type type, double state) {
     case FAST_OUT_SLOW_IN_2:
       return gfx::CubicBezier(0.2, 0, 0.2, 1).Solve(state);
 
+    case FAST_OUT_SLOW_IN_3:
+      return gfx::CubicBezier(0.2, 0, 0, 1).Solve(state);
+
     case LINEAR_OUT_SLOW_IN:
       return gfx::CubicBezier(0, 0, .2, 1).Solve(state);
 

ui/gfx/animation/tween.h

@@ -26,6 +26,9 @@ class ANIMATION_EXPORT Tween {
     EASE_OUT,          // Fast in, slow out (default).
     EASE_OUT_2,        // Variant of EASE_OUT that ends slower than EASE_OUT.
     EASE_OUT_3,        // Variant of EASE_OUT that ends slower than EASE_OUT_2.
+    EASE_OUT_4,        // Variant of EASE_OUT that start slower than EASE_OUT_3,
+                       // and ends faster. Best used to lead into a bounce
+                       // animation.
     EASE_IN,           // Slow in, fast out.
     EASE_IN_2,         // Variant of EASE_IN that starts out slower than
                        // EASE_IN.
@@ -36,6 +39,9 @@ class ANIMATION_EXPORT Tween {
     FAST_OUT_SLOW_IN,  // Variant of EASE_IN_OUT which should be used in most
                        // cases.
     FAST_OUT_SLOW_IN_2,  // Variant of FAST_OUT_SLOW_IN that starts out quicker.
+    FAST_OUT_SLOW_IN_3,  // Variant of FAST_OUT_SLOW_IN that starts out quicker
+                         // than FAST_OUT_SLOW_IN_2. Best used for rebound in
+                         // bounce animation.
     LINEAR_OUT_SLOW_IN,  // Variant of EASE_OUT which should be used for
                          // fading in from 0% or motion when entering a scene.
     SLOW_OUT_LINEAR_IN,  // Reverse of LINEAR_OUT_SLOW_IN which should be used