[CRD iOS] Viewport fling animation

remoting/client/fling_animation.h

+// Copyright 2017 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 REMOTING_CLIENT_FLING_ANIMATION_H_
+#define REMOTING_CLIENT_FLING_ANIMATION_H_
+
+#include "base/callback.h"
+#include "remoting/client/fling_tracker.h"
+
+namespace remoting {
+
+// This class helps interpolating the positions of an object with the given
+// initial velocity and feeds the change in position back to the callback.
+class FlingAnimation {
+ public:
+  using FlingCallback = base::Callback<void(float, float)>;

[nicholss, 2017/05/10 19:34:05]

Can you document the callback please

[Yuwei, 2017/05/10 23:28:24]

Done.

+
+  // FlingCallback: arguments are delta_x and delta_y with respect to the
+  //     positions at previous tick.

[nicholss, 2017/05/10 19:34:05]

running git cl format leaves these spaces?

[Yuwei, 2017/05/10 23:28:24]

I was trying to follow the four-space indenting rule. Not working well though.

I've moved the comment to the callback.

+  FlingAnimation(float time_constant, const FlingCallback& fling_callback);
+  ~FlingAnimation();
+
+  // (Re)starts the fling animation with the given initial velocity.
+  void Reset(float velocity_x, float velocity_y);

[nicholss, 2017/05/10 19:34:05]

rename to setVelocity() ?

[Yuwei, 2017/05/10 23:28:24]

Done.

+
+  bool IsAnimationInProgress() const;
+
+  // Moves forward the animation to catch up with current time. Calls the fling
+  // callback with the new positions. No-op if fling animation is not in
+  // progress.
+  void Tick();
+
+  // Aborts the animation.
+  void Abort();
+
+ private:
+  FlingTracker fling_tracker_;

[nicholss, 2017/05/10 19:34:05]

Forward declare rather than include?

[Yuwei, 2017/05/10 23:28:24]

This is not a pointer nor a reference so forward declaration doesn't work in
this case.

If you insist, I can change this to a unique_ptr.

+  FlingCallback fling_callback_;
+
+  float previous_position_x_ = 0.f;
+  float previous_position_y_ = 0.f;
+
+  // FlingAnimation is neither copyable nor movable.
+  FlingAnimation(const FlingAnimation&) = delete;
+  FlingAnimation& operator=(const FlingAnimation&) = delete;
+};
+
+}  // namespace remoting
+#endif  // REMOTING_CLIENT_FLING_ANIMATION_H_