Home | History | Annotate | Download | only in gesture_detection 
      1 // Copyright 2014 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #include "ui/events/gesture_detection/velocity_tracker_state.h"
      6 
      7 #include "base/logging.h"
      8 #include "ui/events/gesture_detection/motion_event.h"
      9 
     10 namespace ui {
     11 namespace {
     12 // Special constant to request the velocity of the active pointer.
     13 const int ACTIVE_POINTER_ID = -1;
     14 }
     15 
     16 VelocityTrackerState::VelocityTrackerState()
     17     : velocity_tracker_(VelocityTracker::STRATEGY_DEFAULT),
     18       active_pointer_id_(ACTIVE_POINTER_ID) {}
     19 
     20 VelocityTrackerState::VelocityTrackerState(VelocityTracker::Strategy strategy)
     21     : velocity_tracker_(strategy), active_pointer_id_(ACTIVE_POINTER_ID) {}
     22 
     23 VelocityTrackerState::~VelocityTrackerState() {}
     24 
     25 void VelocityTrackerState::Clear() {
     26   velocity_tracker_.Clear();
     27   active_pointer_id_ = ACTIVE_POINTER_ID;
     28   calculated_id_bits_.clear();
     29 }
     30 
     31 void VelocityTrackerState::AddMovement(const MotionEvent& event) {
     32   velocity_tracker_.AddMovement(event);
     33 }
     34 
     35 void VelocityTrackerState::ComputeCurrentVelocity(int32_t units,
     36                                                   float max_velocity) {
     37   DCHECK_GE(max_velocity, 0);
     38 
     39   BitSet32 id_bits(velocity_tracker_.GetCurrentPointerIdBits());
     40   calculated_id_bits_ = id_bits;
     41 
     42   for (uint32_t index = 0; !id_bits.is_empty(); index++) {
     43     uint32_t id = id_bits.clear_first_marked_bit();
     44 
     45     float vx, vy;
     46     velocity_tracker_.GetVelocity(id, &vx, &vy);
     47 
     48     vx = vx * units / 1000.f;
     49     vy = vy * units / 1000.f;
     50 
     51     if (vx > max_velocity)
     52       vx = max_velocity;
     53     else if (vx < -max_velocity)
     54       vx = -max_velocity;
     55 
     56     if (vy > max_velocity)
     57       vy = max_velocity;
     58     else if (vy < -max_velocity)
     59       vy = -max_velocity;
     60 
     61     Velocity& velocity = calculated_velocity_[index];
     62     velocity.vx = vx;
     63     velocity.vy = vy;
     64   }
     65 }
     66 
     67 float VelocityTrackerState::GetXVelocity(int32_t id) const {
     68   float vx;
     69   GetVelocity(id, &vx, NULL);
     70   return vx;
     71 }
     72 
     73 float VelocityTrackerState::GetYVelocity(int32_t id) const {
     74   float vy;
     75   GetVelocity(id, NULL, &vy);
     76   return vy;
     77 }
     78 
     79 void VelocityTrackerState::GetVelocity(int32_t id,
     80                                        float* out_vx,
     81                                        float* out_vy) const {
     82   DCHECK(out_vx || out_vy);
     83   if (id == ACTIVE_POINTER_ID)
     84     id = velocity_tracker_.GetActivePointerId();
     85 
     86   float vx, vy;
     87   if (id >= 0 && id <= MotionEvent::MAX_POINTER_ID &&
     88       calculated_id_bits_.has_bit(id)) {
     89     uint32_t index = calculated_id_bits_.get_index_of_bit(id);
     90     const Velocity& velocity = calculated_velocity_[index];
     91     vx = velocity.vx;
     92     vy = velocity.vy;
     93   } else {
     94     vx = 0;
     95     vy = 0;
     96   }
     97 
     98   if (out_vx)
     99     *out_vx = vx;
    100 
    101   if (out_vy)
    102     *out_vy = vy;
    103 }
    104 
    105 }  // namespace ui
    106