| // 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 UI_EVENTS_GESTURE_DETECTION_VELOCITY_TRACKER_H_ |
| #define UI_EVENTS_GESTURE_DETECTION_VELOCITY_TRACKER_H_ |
| |
| #include "base/basictypes.h" |
| #include "base/memory/scoped_ptr.h" |
| #include "base/time/time.h" |
| #include "ui/events/gesture_detection/bitset_32.h" |
| |
| namespace ui { |
| |
| class MotionEvent; |
| class VelocityTrackerStrategy; |
| |
| namespace { |
| struct Estimator; |
| struct Position; |
| } |
| |
| // Port of VelocityTracker from Android |
| // * platform/frameworks/native/include/input/VelocityTracker.h |
| // * Change-Id: I4983db61b53e28479fc90d9211fafff68f7f49a6 |
| // * Please update the Change-Id as upstream Android changes are pulled. |
| class VelocityTracker { |
| public: |
| enum { |
| // The maximum number of pointers to use when computing the velocity. |
| // Note that the supplied MotionEvent may expose more than 16 pointers, but |
| // at most |MAX_POINTERS| will be used. |
| MAX_POINTERS = 16, |
| }; |
| |
| enum Strategy { |
| // 1st order least squares. Quality: POOR. |
| // Frequently underfits the touch data especially when the finger |
| // accelerates or changes direction. Often underestimates velocity. The |
| // direction is overly influenced by historical touch points. |
| LSQ1, |
| |
| // 2nd order least squares. Quality: VERY GOOD. |
| // Pretty much ideal, but can be confused by certain kinds of touch data, |
| // particularly if the panel has a tendency to generate delayed, |
| // duplicate or jittery touch coordinates when the finger is released. |
| LSQ2, |
| |
| // 3rd order least squares. Quality: UNUSABLE. |
| // Frequently overfits the touch data yielding wildly divergent estimates |
| // of the velocity when the finger is released. |
| LSQ3, |
| |
| // 2nd order weighted least squares, delta weighting. |
| // Quality: EXPERIMENTAL |
| WLSQ2_DELTA, |
| |
| // 2nd order weighted least squares, central weighting. |
| // Quality: EXPERIMENTAL |
| WLSQ2_CENTRAL, |
| |
| // 2nd order weighted least squares, recent weighting. |
| // Quality: EXPERIMENTAL |
| WLSQ2_RECENT, |
| |
| // 1st order integrating filter. Quality: GOOD. |
| // Not as good as 'lsq2' because it cannot estimate acceleration but it is |
| // more tolerant of errors. Like 'lsq1', this strategy tends to |
| // underestimate |
| // the velocity of a fling but this strategy tends to respond to changes in |
| // direction more quickly and accurately. |
| INT1, |
| |
| // 2nd order integrating filter. Quality: EXPERIMENTAL. |
| // For comparison purposes only. Unlike 'int1' this strategy can compensate |
| // for acceleration but it typically overestimates the effect. |
| INT2, |
| STRATEGY_MAX = INT2, |
| |
| // The default velocity tracker strategy. |
| // Although other strategies are available for testing and comparison |
| // purposes, this is the strategy that applications will actually use. Be |
| // very careful when adjusting the default strategy because it can |
| // dramatically affect (often in a bad way) the user experience. |
| STRATEGY_DEFAULT = LSQ2, |
| }; |
| |
| // 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(Strategy 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; |
| |
| base::TimeTicks last_event_time_; |
| BitSet32 current_pointer_id_bits_; |
| int32_t active_pointer_id_; |
| scoped_ptr<VelocityTrackerStrategy> strategy_; |
| |
| DISALLOW_COPY_AND_ASSIGN(VelocityTracker); |
| }; |
| |
| } // namespace ui |
| |
| #endif // UI_EVENTS_GESTURE_DETECTION_VELOCITY_TRACKER_H_ |