Expand the Material Design hover as it fades out when a ripple is triggered.

ui/views/animation/ink_drop_hover.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_VIEWS_ANIMATION_INK_DROP_HOVER_H_
 #define UI_VIEWS_ANIMATION_INK_DROP_HOVER_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "base/time/time.h"
 #include "third_party/skia/include/core/SkColor.h"
 #include "ui/gfx/geometry/point.h"
+#include "ui/gfx/geometry/point_f.h"
 #include "ui/gfx/geometry/size.h"
+#include "ui/gfx/geometry/size_f.h"
+#include "ui/gfx/transform.h"
 #include "ui/views/views_export.h"
 
 namespace ui {
 class Layer;
 class CallbackLayerAnimationObserver;
 }  // namespace ui
 
 namespace views {
 class RoundedRectangleLayerDelegate;
 
 // Manages fade in/out animations for a painted Layer that is used to provide
 // visual feedback on ui::Views for mouse hover states.
 class VIEWS_EXPORT InkDropHover {
  public:
   InkDropHover(const gfx::Size& size,
                int corner_radius,
                const gfx::Point& center_point,
                SkColor color);
   ~InkDropHover();
 
+  void set_explode_size(const gfx::SizeF& size) { explode_size_ = size; }

[varkha, 2016/04/21 16:16:49]

Do you think this class should decide to use Size vs. SizeF (not necessarily in
this CL)?

[varkha, 2016/04/21 16:16:49]

It may be simpler (less flexible but I don't think you have non-equal horizontal
and vertical scaling now anyway) to pass around scale factor rather than
gfx::Size. I think this will save on how many places calculate the scale factor.

[bruthig, 2016/04/21 21:14:04]

Updated to use Size.

[bruthig, 2016/04/21 21:14:04]

Discussed with varkha@ offline.  We will defer deciding on this until we have
decided whether we can/cannot optimize by painting to a smaller Layer.

+
   // Returns true if the hover animation is either in the process of fading
   // in or is fully visible.
   bool IsFadingInOrVisible() const;
 
   // Fades in the hover visual over the given |duration|.
   void FadeIn(const base::TimeDelta& duration);
 
   // Fades out the hover visual over the given |duration|.

[varkha, 2016/04/21 16:16:49]

nit: Document |explode|.

[bruthig, 2016/04/21 21:14:04]

Done.

-  void FadeOut(const base::TimeDelta& duration);
+  void FadeOut(const base::TimeDelta& duration, bool explode);
 
   // The root Layer that can be added in to a Layer tree.
   ui::Layer* layer() { return layer_.get(); }
 
  private:
   enum HoverAnimationType { FADE_IN, FADE_OUT };
 
-  // Animates a fade in/out as specified by |animation_type| over the given
-  // |duration|.
+  // Animates a fade in/out as specified by |animation_type| combined with a
+  // transformation from the |initial_transform| to the |target_transform| over
+  // the given |duration|.
   void AnimateFade(HoverAnimationType animation_type,
-                   const base::TimeDelta& duration);
+                   const base::TimeDelta& duration,
+                   const gfx::Transform& initial_transform,
+                   const gfx::Transform& target_transform);
+
+  // Calculates the Transform to apply to |layer_| for the given |size|.
+  gfx::Transform CalculateTransform(const gfx::SizeF& size) const;
 
   // The callback that will be invoked when a fade in/out animation is complete.
   bool AnimationEndedCallback(
       HoverAnimationType animation_type,
       const ui::CallbackLayerAnimationObserver& observer);
 
+  // The size of the hover shape when fully faded in.
+  gfx::SizeF size_;
+
+  // The target size of the hover shape when it expands during a fade out
+  // animation.
+  gfx::SizeF explode_size_;
+
+  // The center point of the hover shape in the parent Layer's coordinate space.
+  gfx::PointF center_point_;
+
   // True if the last animation to be initiated was a FADE_IN, and false
   // otherwise.
   bool last_animation_initiated_was_fade_in_;
 
   // The LayerDelegate that paints the hover |layer_|.
   std::unique_ptr<RoundedRectangleLayerDelegate> layer_delegate_;
 
   // The visual hover layer that is painted by |layer_delegate_|.
   std::unique_ptr<ui::Layer> layer_;
 
   DISALLOW_COPY_AND_ASSIGN(InkDropHover);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_ANIMATION_INK_DROP_HOVER_H_