Add overscroll edge effect animations for Android.

content/browser/android/overscroll_glow.h

+// Copyright (c) 2012 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 CONTENT_BROWSER_ANDROID_OVERSCROLL_GLOW_H_
+#define CONTENT_BROWSER_ANDROID_OVERSCROLL_GLOW_H_
+
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/time.h"
+#include "content/browser/android/edge_effect.h"
+#include "ui/gfx/size_f.h"
+#include "ui/gfx/vector2d_f.h"
+
+class SkBitmap;
+
+namespace cc {
+class Layer;
+}
+
+namespace content {
+
+/* |OverscrollGlow| mirrors its Android counterpart, EdgeEffect.java.
+ * Conscious tradeoffs were made to align this as closely as possible with the
+ * original Android java version.
+ */
+class OverscrollGlow {
+ public:
+  static scoped_ptr<OverscrollGlow> Create();
+
+  ~OverscrollGlow();
+
+  void OnOverscrolled(base::TimeTicks current_time,
+                      gfx::Vector2dF overscroll,
+                      gfx::Vector2dF velocity);
+  // Returns true if the effect still needs animation ticks.
+  bool Animate(base::TimeTicks current_time);
+  void Finish();
+
+  // Returns true if the effect needs animation ticks.
+  bool IsActive() const;
+
+  void set_horizontal_overscroll_enabled(bool enabled);

[no sievers, 2013/05/13 18:38:24]

nit: SetHorizontalOverscrollEnabled(), and same for other methods.

[jdduke (slow), 2013/05/13 20:44:24]

Why? It's a trivial setter?

[no sievers, 2013/05/13 20:53:22]

I think lower-case with underscores is normally used with inline functions only
though.

+  void set_vertical_overscroll_enabled(bool enabled);
+  void set_size(gfx::SizeF size);
+  void set_parent_layer(scoped_refptr<cc::Layer> parent_layer);
+
+ private:
+  enum Axis { AXIS_X, AXIS_Y };
+
+  OverscrollGlow(const SkBitmap& edge, const SkBitmap& glow);
+
+  void Pull(base::TimeTicks current_time,
+            gfx::Vector2dF added_overscroll);
+  void Absorb(base::TimeTicks current_time,
+              gfx::Vector2dF velocity,
+              gfx::Vector2dF overscroll,
+              gfx::Vector2dF old_overscroll);
+
+  void Release(base::TimeTicks current_time);
+  void Release(Axis axis, base::TimeTicks current_time);
+
+  EdgeEffect* GetOppositeEdge(int edge_index);
+
+  scoped_ptr<EdgeEffect> edge_effects_[EdgeEffect::EDGE_COUNT];
+
+  gfx::SizeF size_;
+  gfx::Vector2dF old_overscroll_;
+  gfx::Vector2dF old_velocity_;
+  bool horizontal_overscroll_enabled_;
+  bool vertical_overscroll_enabled_;
+
+  scoped_refptr<cc::Layer> parent_layer_;
+
+  DISALLOW_COPY_AND_ASSIGN(OverscrollGlow);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_ANDROID_SCROLL_GLOW_H_