ui/events/gesture_detection/scale_gesture_detector.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/scale_gesture_detector.h"
   6
   7 #include <limits.h>
   8 #include <cmath>
   9
  10 #include "base/float_util.h"
  11 #include "base/logging.h"
  12 #include "ui/events/gesture_detection/motion_event.h"
  13
  14 using base::TimeDelta;
  15 using base::TimeTicks;
  16
  17 namespace ui {
  18 namespace {
  19
  20 // Using a small epsilon when comparing slop distances allows pixel perfect
  21 // slop determination when using fractional DPI coordinates (assuming the slop
  22 // region and DPI scale are reasonably proportioned).
  23 const float kSlopEpsilon = .05f;
  24
  25 const int kTouchStabilizeTimeMs = 128;
  26
  27 const float kScaleFactor = .5f;
  28
  29 }  // namespace
  30
  31 // Note: These constants were taken directly from the default (unscaled)
  32 // versions found in Android's ViewConfiguration.
  33 ScaleGestureDetector::Config::Config()
  34     : span_slop(16),
  35       min_scaling_touch_major(48),
  36       min_scaling_span(200),
  37       min_pinch_update_span_delta(0) {
  38 }
  39
  40 ScaleGestureDetector::Config::~Config() {}
  41
  42 bool ScaleGestureDetector::SimpleScaleGestureListener::OnScale(
  43     const ScaleGestureDetector&, const MotionEvent&) {
  44   return false;
  45 }
  46
  47 bool ScaleGestureDetector::SimpleScaleGestureListener::OnScaleBegin(
  48     const ScaleGestureDetector&, const MotionEvent&) {
  49   return true;
  50 }
  51
  52 void ScaleGestureDetector::SimpleScaleGestureListener::OnScaleEnd(
  53     const ScaleGestureDetector&, const MotionEvent&) {}
  54
  55 ScaleGestureDetector::ScaleGestureDetector(const Config& config,
  56                                            ScaleGestureListener* listener)
  57     : listener_(listener),
  58       focus_x_(0),
  59       focus_y_(0),
  60       curr_span_(0),
  61       prev_span_(0),
  62       initial_span_(0),
  63       curr_span_x_(0),
  64       curr_span_y_(0),
  65       prev_span_x_(0),
  66       prev_span_y_(0),
  67       in_progress_(0),
  68       span_slop_(0),
  69       min_span_(0),
  70       touch_upper_(0),
  71       touch_lower_(0),
  72       touch_history_last_accepted_(0),
  73       touch_history_direction_(0),
  74       touch_min_major_(0),
  75       touch_max_major_(0),
  76       double_tap_focus_x_(0),
  77       double_tap_focus_y_(0),
  78       double_tap_mode_(DOUBLE_TAP_MODE_NONE),
  79       event_before_or_above_starting_gesture_event_(false) {
  80   DCHECK(listener_);
  81   span_slop_ = config.span_slop + kSlopEpsilon;
  82   touch_min_major_ = config.min_scaling_touch_major;
  83   touch_max_major_ = std::min(config.min_scaling_span / std::sqrt(2.f),
  84                               2.f * touch_min_major_);
  85   min_span_ = config.min_scaling_span + kSlopEpsilon;
  86   ResetTouchHistory();
  87 }
  88
  89 ScaleGestureDetector::~ScaleGestureDetector() {}
  90
  91 bool ScaleGestureDetector::OnTouchEvent(const MotionEvent& event) {
  92   curr_time_ = event.GetEventTime();
  93
  94   const int action = event.GetAction();
  95
  96   const bool stream_complete =
  97       action == MotionEvent::ACTION_UP ||
  98       action == MotionEvent::ACTION_CANCEL ||
  99       (action == MotionEvent::ACTION_POINTER_DOWN && InDoubleTapMode());
 100
 101   if (action == MotionEvent::ACTION_DOWN || stream_complete) {
 102     // Reset any scale in progress with the listener.
 103     // If it's an ACTION_DOWN we're beginning a new event stream.
 104     // This means the app probably didn't give us all the events. Shame on it.
 105     if (in_progress_) {
 106       listener_->OnScaleEnd(*this, event);
 107       ResetScaleWithSpan(0);
 108     } else if (InDoubleTapMode() && stream_complete) {
 109       ResetScaleWithSpan(0);
 110     }
 111
 112     if (stream_complete) {
 113       ResetTouchHistory();
 114       return true;
 115     }
 116   }
 117
 118   const bool config_changed = action == MotionEvent::ACTION_DOWN ||
 119                               action == MotionEvent::ACTION_POINTER_UP ||
 120                               action == MotionEvent::ACTION_POINTER_DOWN;
 121
 122   const bool pointer_up = action == MotionEvent::ACTION_POINTER_UP;
 123   const int skip_index = pointer_up ? event.GetActionIndex() : -1;
 124
 125   // Determine focal point.
 126   float sum_x = 0, sum_y = 0;
 127   const int count = static_cast<int>(event.GetPointerCount());
 128   const int unreleased_point_count = pointer_up ? count - 1 : count;
 129   const float inverse_unreleased_point_count = 1.0f / unreleased_point_count;
 130
 131   float focus_x;
 132   float focus_y;
 133   if (InDoubleTapMode()) {
 134     // In double tap mode, the focal pt is always where the double tap
 135     // gesture started.
 136     focus_x = double_tap_focus_x_;
 137     focus_y = double_tap_focus_y_;
 138     if (event.GetY() < focus_y) {
 139       event_before_or_above_starting_gesture_event_ = true;
 140     } else {
 141       event_before_or_above_starting_gesture_event_ = false;
 142     }
 143   } else {
 144     for (int i = 0; i < count; i++) {
 145       if (skip_index == i)
 146         continue;
 147       sum_x += event.GetX(i);
 148       sum_y += event.GetY(i);
 149     }
 150
 151     focus_x = sum_x * inverse_unreleased_point_count;
 152     focus_y = sum_y * inverse_unreleased_point_count;
 153   }
 154
 155   AddTouchHistory(event);
 156
 157   // Determine average deviation from focal point.
 158   float dev_sum_x = 0, dev_sum_y = 0;
 159   for (int i = 0; i < count; i++) {
 160     if (skip_index == i)
 161       continue;
 162
 163     dev_sum_x += std::abs(event.GetX(i) - focus_x);
 164     dev_sum_y += std::abs(event.GetY(i) - focus_y);
 165   }
 166   // Convert the resulting diameter into a radius, to include touch
 167   // radius in overall deviation.
 168   const float touch_radius = touch_history_last_accepted_ / 2;
 169
 170   const float dev_x = dev_sum_x * inverse_unreleased_point_count + touch_radius;
 171   const float dev_y = dev_sum_y * inverse_unreleased_point_count + touch_radius;
 172
 173   // Span is the average distance between touch points through the focal point;
 174   // i.e. the diameter of the circle with a radius of the average deviation from
 175   // the focal point.
 176   const float span_x = dev_x * 2;
 177   const float span_y = dev_y * 2;
 178   float span;
 179   if (InDoubleTapMode()) {
 180     span = span_y;
 181   } else {
 182     span = std::sqrt(span_x * span_x + span_y * span_y);
 183   }
 184
 185   // Dispatch begin/end events as needed.
 186   // If the configuration changes, notify the app to reset its current state by
 187   // beginning a fresh scale event stream.
 188   const bool was_in_progress = in_progress_;
 189   focus_x_ = focus_x;
 190   focus_y_ = focus_y;
 191   if (!InDoubleTapMode() && in_progress_ &&
 192       (span < min_span_ || config_changed)) {
 193     listener_->OnScaleEnd(*this, event);
 194     ResetScaleWithSpan(span);
 195   }
 196   if (config_changed) {
 197     prev_span_x_ = curr_span_x_ = span_x;
 198     prev_span_y_ = curr_span_y_ = span_y;
 199     initial_span_ = prev_span_ = curr_span_ = span;
 200   }
 201
 202   const float min_span = InDoubleTapMode() ? span_slop_ : min_span_;
 203   if (!in_progress_ && span >= min_span &&
 204       (was_in_progress || std::abs(span - initial_span_) > span_slop_)) {
 205     prev_span_x_ = curr_span_x_ = span_x;
 206     prev_span_y_ = curr_span_y_ = span_y;
 207     prev_span_ = curr_span_ = span;
 208     prev_time_ = curr_time_;
 209     in_progress_ = listener_->OnScaleBegin(*this, event);
 210   }
 211
 212   // Handle motion; focal point and span/scale factor are changing.
 213   if (action == MotionEvent::ACTION_MOVE) {
 214     curr_span_x_ = span_x;
 215     curr_span_y_ = span_y;
 216     curr_span_ = span;
 217
 218     bool update_prev = true;
 219
 220     if (in_progress_) {
 221       update_prev = listener_->OnScale(*this, event);
 222     }
 223
 224     if (update_prev) {
 225       prev_span_x_ = curr_span_x_;
 226       prev_span_y_ = curr_span_y_;
 227       prev_span_ = curr_span_;
 228       prev_time_ = curr_time_;
 229     }
 230   }
 231
 232   return true;
 233 }
 234
 235 bool ScaleGestureDetector::IsInProgress() const { return in_progress_; }
 236
 237 bool ScaleGestureDetector::InDoubleTapMode() const {
 238   return double_tap_mode_ == DOUBLE_TAP_MODE_IN_PROGRESS;
 239 }
 240
 241 float ScaleGestureDetector::GetFocusX() const { return focus_x_; }
 242
 243 float ScaleGestureDetector::GetFocusY() const { return focus_y_; }
 244
 245 float ScaleGestureDetector::GetCurrentSpan() const { return curr_span_; }
 246
 247 float ScaleGestureDetector::GetCurrentSpanX() const { return curr_span_x_; }
 248
 249 float ScaleGestureDetector::GetCurrentSpanY() const { return curr_span_y_; }
 250
 251 float ScaleGestureDetector::GetPreviousSpan() const { return prev_span_; }
 252
 253 float ScaleGestureDetector::GetPreviousSpanX() const { return prev_span_x_; }
 254
 255 float ScaleGestureDetector::GetPreviousSpanY() const { return prev_span_y_; }
 256
 257 float ScaleGestureDetector::GetScaleFactor() const {
 258   if (InDoubleTapMode()) {
 259     // Drag is moving up; the further away from the gesture start, the smaller
 260     // the span should be, the closer, the larger the span, and therefore the
 261     // larger the scale.
 262     const bool scale_up = (event_before_or_above_starting_gesture_event_ &&
 263                            (curr_span_ < prev_span_)) ||
 264                           (!event_before_or_above_starting_gesture_event_ &&
 265                            (curr_span_ > prev_span_));
 266     const float span_diff =
 267         (std::abs(1.f - (curr_span_ / prev_span_)) * kScaleFactor);
 268     return prev_span_ <= 0 ? 1.f
 269                            : (scale_up ? (1.f + span_diff) : (1.f - span_diff));
 270   }
 271   return prev_span_ > 0 ? curr_span_ / prev_span_ : 1;
 272 }
 273
 274 base::TimeDelta ScaleGestureDetector::GetTimeDelta() const {
 275   return curr_time_ - prev_time_;
 276 }
 277
 278 base::TimeTicks ScaleGestureDetector::GetEventTime() const {
 279   return curr_time_;
 280 }
 281
 282 bool ScaleGestureDetector::OnDoubleTap(const MotionEvent& ev) {
 283   // Double tap: start watching for a swipe.
 284   double_tap_focus_x_ = ev.GetX();
 285   double_tap_focus_y_ = ev.GetY();
 286   double_tap_mode_ = DOUBLE_TAP_MODE_IN_PROGRESS;
 287   return true;
 288 }
 289
 290 void ScaleGestureDetector::AddTouchHistory(const MotionEvent& ev) {
 291   const base::TimeTicks current_time = ev.GetEventTime();
 292   DCHECK(!current_time.is_null());
 293   const int count = static_cast<int>(ev.GetPointerCount());
 294   bool accept = touch_history_last_accepted_time_.is_null() ||
 295                 (current_time - touch_history_last_accepted_time_) >=
 296                     base::TimeDelta::FromMilliseconds(kTouchStabilizeTimeMs);
 297   float total = 0;
 298   int sample_count = 0;
 299   for (int i = 0; i < count; i++) {
 300     const bool has_last_accepted = !base::IsNaN(touch_history_last_accepted_);
 301     const int history_size = static_cast<int>(ev.GetHistorySize());
 302     const int pointersample_count = history_size + 1;
 303     for (int h = 0; h < pointersample_count; h++) {
 304       float major;
 305       if (h < history_size) {
 306         major = ev.GetHistoricalTouchMajor(i, h);
 307       } else {
 308         major = ev.GetTouchMajor(i);
 309       }
 310       if (major < touch_min_major_)
 311         major = touch_min_major_;
 312       if (major > touch_max_major_)
 313         major = touch_max_major_;
 314       total += major;
 315
 316       if (base::IsNaN(touch_upper_) || major > touch_upper_) {
 317         touch_upper_ = major;
 318       }
 319       if (base::IsNaN(touch_lower_) || major < touch_lower_) {
 320         touch_lower_ = major;
 321       }
 322
 323       if (has_last_accepted) {
 324         const float major_delta = major - touch_history_last_accepted_;
 325         const int direction_sig =
 326             major_delta > 0 ? 1 : (major_delta < 0 ? -1 : 0);
 327         if (direction_sig != touch_history_direction_ ||
 328             (direction_sig == 0 && touch_history_direction_ == 0)) {
 329           touch_history_direction_ = direction_sig;
 330           touch_history_last_accepted_time_ = h < history_size
 331                                                   ? ev.GetHistoricalEventTime(h)
 332                                                   : ev.GetEventTime();
 333           accept = false;
 334         }
 335       }
 336     }
 337     sample_count += pointersample_count;
 338   }
 339
 340   const float avg = total / sample_count;
 341
 342   if (accept) {
 343     float new_accepted = (touch_upper_ + touch_lower_ + avg) / 3;
 344     touch_upper_ = (touch_upper_ + new_accepted) / 2;
 345     touch_lower_ = (touch_lower_ + new_accepted) / 2;
 346     touch_history_last_accepted_ = new_accepted;
 347     touch_history_direction_ = 0;
 348     touch_history_last_accepted_time_ = ev.GetEventTime();
 349   }
 350 }
 351
 352 void ScaleGestureDetector::ResetTouchHistory() {
 353   touch_upper_ = std::numeric_limits<float>::quiet_NaN();
 354   touch_lower_ = std::numeric_limits<float>::quiet_NaN();
 355   touch_history_last_accepted_ = std::numeric_limits<float>::quiet_NaN();
 356   touch_history_direction_ = 0;
 357   touch_history_last_accepted_time_ = base::TimeTicks();
 358 }
 359
 360 void ScaleGestureDetector::ResetScaleWithSpan(float span) {
 361   in_progress_ = false;
 362   initial_span_ = span;
 363   double_tap_mode_ = DOUBLE_TAP_MODE_NONE;
 364 }
 365
 366 }  // namespace ui