Add overscroll edge effect animations for Android.

content/browser/android/edge_effect.h

+// Copyright (c) 2013 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_EDGE_EFFECT_H_
+#define CONTENT_BROWSER_ANDROID_EDGE_EFFECT_H_
+
+#include "base/basictypes.h"
+#include "base/memory/ref_counted.h"
+#include "base/time.h"
+#include "ui/gfx/size_f.h"
+
+namespace cc {
+class Layer;
+}
+
+namespace content {
+
+/* |EdgeEffect| mirrors its Android counterpart, EdgeEffect.java.
+ * The primary difference is ownership; the Android version manages render
+ * resources directly, while this version simply applies the effect to
+ * existing resources. Conscious tradeoffs were made to align this as closely
+ * as possible with the original Android java version.
+ */
+class EdgeEffect {
+public:
+  enum Edge {
+    EDGE_TOP = 0,
+    EDGE_LEFT,
+    EDGE_BOTTOM,
+    EDGE_RIGHT,
+    EDGE_COUNT
+  };
+
+  EdgeEffect(scoped_refptr<cc::Layer> edge, scoped_refptr<cc::Layer> glow);
+  ~EdgeEffect();
+
+  void Pull(base::TimeTicks current_time, float delta_distance);
+  void Absorb(base::TimeTicks current_time, float velocity);
+  bool Update(base::TimeTicks current_time);
+  void Release(base::TimeTicks current_time);
+
+  void Finish();
+  bool IsFinished() const;
+
+  void Draw(cc::Layer* parent_layer, gfx::SizeF size, Edge edge);

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

Should this be called something other than Draw(), maybe Animate()? Or collapse
with Update() since that all seems to be the same stage?

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

Yeah, I went back and forth on this, particularly when the layers were owned by
the parent.  I wouldn't mind keeping the logical updates separate from the layer
updates, but "Draw" is probably a bad name here.  What about "ApplyToLayers" or
"UpdateLayers"?

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

I like ApplyToLayers().

+
+private:
+
+  enum State {
+    STATE_IDLE = 0,
+    STATE_PULL,
+    STATE_ABSORB,
+    STATE_RECEDE,
+    STATE_PULL_DECAY
+  };
+
+  void Attach(cc::Layer* parent_layer);
+  void Detach();
+
+  scoped_refptr<cc::Layer> edge_;
+  scoped_refptr<cc::Layer> glow_;
+
+  float edge_alpha_;
+  float edge_scale_y_;
+  float glow_alpha_;
+  float glow_scale_y_;
+
+  float edge_alpha_start_;
+  float edge_alpha_finish_;
+  float edge_scale_y_start_;
+  float edge_scale_y_finish_;
+  float glow_alpha_start_;
+  float glow_alpha_finish_;
+  float glow_scale_y_start_;
+  float glow_scale_y_finish_;
+
+  base::TimeTicks start_time_;
+  base::TimeDelta duration_;
+
+  State state_;
+
+  float pull_distance_;
+
+  DISALLOW_COPY_AND_ASSIGN(EdgeEffect);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_ANDROID_EDGE_EFFECT_H_