[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 <memory>
+
+#include "base/callback.h"
+#include "base/time/tick_clock.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:
+  // arguments are delta_x and delta_y with respect to the positions at previous
+  // tick.
+  using FlingCallback = base::Callback<void(float, float)>;
+
+  FlingAnimation(float time_constant, const FlingCallback& fling_callback);
+  ~FlingAnimation();
+
+  // (Re)starts the fling animation with the given initial velocity.
+  void SetVelocity(float velocity_x, float velocity_y);
+
+  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();
+
+  void SetTickClockForTest(std::unique_ptr<base::TickClock> clock);
+
+ private:
+  FlingTracker fling_tracker_;
+  FlingCallback fling_callback_;
+
+  base::TimeTicks fling_start_time_;
+
+  std::unique_ptr<base::TickClock> clock_;
+
+  // FlingAnimation is neither copyable nor movable.
+  FlingAnimation(const FlingAnimation&) = delete;
+  FlingAnimation& operator=(const FlingAnimation&) = delete;
+};
+
+}  // namespace remoting
+#endif  // REMOTING_CLIENT_FLING_ANIMATION_H_