[Tracking Patch] Unified gesture detection

content/browser/renderer_host/input/gestures/velocity_tracker.h

+// Copyright 2014 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_RENDERER_HOST_INPUT_GESTURES_VELOCITY_TRACKER_H_
+#define CONTENT_BROWSER_RENDERER_HOST_INPUT_GESTURES_VELOCITY_TRACKER_H_
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/time/time.h"
+#include "content/browser/renderer_host/input/gestures/bitset_32.h"
+
+namespace content {
+
+class MotionEvent;
+class VelocityTrackerStrategy;
+
+namespace {
+struct Estimator;
+}
+
+// Port of VelocityTracker from Android
+// * platform/frameworks/native/include/input/VelocityTracker.h
+// * Change-Id: I4983db61b53e28479fc90d9211fafff68f7f49a6
+// * Changes to this class should be cosmetic only, easing fork maintenance.
+class VelocityTracker {
+public:
+  struct Position {
+    float x, y;
+  };
+
+  enum {
+    MAX_POINTERS = 16,
+    MAX_POINTER_ID = 31
+  };
+
+  // Creates a velocity tracker using the default strategy for the platform.
+  VelocityTracker();
+
+  // Creates a velocity tracker using the specified strategy.
+  // If strategy is NULL, uses the default strategy for the platform.
+  explicit VelocityTracker(const char* strategy);
+
+  ~VelocityTracker();
+
+  // Resets the velocity tracker state.
+  void Clear();
+
+  // Adds movement information for all pointers in a MotionEvent, including
+  // historical samples.
+  void AddMovement(const MotionEvent& event);
+
+  // Gets the velocity of the specified pointer id in position units per second.
+  // Returns false and sets the velocity components to zero if there is
+  // insufficient movement information for the pointer.
+  bool GetVelocity(uint32_t id, float* outVx, float* outVy) const;
+
+  // Gets the active pointer id, or -1 if none.
+  inline int32_t GetActivePointerId() const { return active_pointer_id_; }
+
+  // Gets a bitset containing all pointer ids from the most recent movement.
+  inline BitSet32 GetCurrentPointerIdBits() const {
+    return current_pointer_id_bits_;
+  }
+
+ private:
+  // Resets the velocity tracker state for specific pointers.
+  // Call this method when some pointers have changed and may be reusing
+  // an id that was assigned to a different pointer earlier.
+  void ClearPointers(BitSet32 id_bits);
+
+  // Adds movement information for a set of pointers.
+  // The id_bits bitfield specifies the pointer ids of the pointers whose
+  // positions
+  // are included in the movement.
+  // The positions array contains position information for each pointer in order
+  // by
+  // increasing id.  Its size should be equal to the number of one bits in
+  // id_bits.
+  void AddMovement(const base::TimeTicks& event_time,
+                   BitSet32 id_bits,
+                   const Position* positions);
+
+  // Gets an estimator for the recent movements of the specified pointer id.
+  // Returns false and clears the estimator if there is no information available
+  // about the pointer.
+  bool GetEstimator(uint32_t id, Estimator* out_estimator) const;
+
+  bool ConfigureStrategy(const char* strategy);
+
+  static VelocityTrackerStrategy* CreateStrategy(const char* strategy);
+
+  base::TimeTicks last_event_time_;
+  BitSet32 current_pointer_id_bits_;
+  int32_t active_pointer_id_;
+  scoped_ptr<VelocityTrackerStrategy> strategy_;
+};
+
+// Implements a particular velocity tracker algorithm.
+class VelocityTrackerStrategy {
+ public:
+  virtual ~VelocityTrackerStrategy() {}
+
+  virtual void Clear() = 0;
+  virtual void ClearPointers(BitSet32 id_bits) = 0;
+  virtual void AddMovement(const base::TimeTicks& event_time,
+                           BitSet32 id_bits,
+                           const VelocityTracker::Position* positions) = 0;
+  virtual bool GetEstimator(uint32_t id, Estimator* out_estimator) const = 0;
+
+ protected:
+  VelocityTrackerStrategy() {}
+};
+
+}  // namespace content
+
+#endif // CONTENT_BROWSER_RENDERER_HOST_INPUT_GESTURES_VELOCITY_TRACKER_H_