ui/events/gesture_detection/velocity_tracker_state.cc

   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