Avoid an extra GestureDetector instance for double-tap drag zooming

ui/events/gesture_detection/scale_gesture_detector.cc

 // 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.
 
 #include "ui/events/gesture_detection/scale_gesture_detector.h"
 
 #include <limits.h>
 #include <cmath>
 
 #include "base/float_util.h"
@@ skipping 13 matching lines @@
 
 const int kTouchStabilizeTimeMs = 128;
 
 const float kScaleFactor = .5f;
 
 }  // namespace
 
 // Note: These constants were taken directly from the default (unscaled)
 // versions found in Android's ViewConfiguration.
 ScaleGestureDetector::Config::Config()
-    : min_scaling_touch_major(48),
+    : span_slop(16),
+      min_scaling_touch_major(48),
       min_scaling_span(200),
-      quick_scale_enabled(true),
       min_pinch_update_span_delta(0) {
 }
 
 ScaleGestureDetector::Config::~Config() {}
 
 bool ScaleGestureDetector::SimpleScaleGestureListener::OnScale(
     const ScaleGestureDetector&, const MotionEvent&) {
   return false;
 }
 
 bool ScaleGestureDetector::SimpleScaleGestureListener::OnScaleBegin(
     const ScaleGestureDetector&, const MotionEvent&) {
   return true;
 }
 
 void ScaleGestureDetector::SimpleScaleGestureListener::OnScaleEnd(
     const ScaleGestureDetector&, const MotionEvent&) {}
 
 ScaleGestureDetector::ScaleGestureDetector(const Config& config,
                                            ScaleGestureListener* listener)
     : listener_(listener),
-      config_(config),
       focus_x_(0),
       focus_y_(0),
-      quick_scale_enabled_(false),
       curr_span_(0),
       prev_span_(0),
       initial_span_(0),
       curr_span_x_(0),
       curr_span_y_(0),
       prev_span_x_(0),
       prev_span_y_(0),
       in_progress_(0),
       span_slop_(0),
       min_span_(0),
       touch_upper_(0),
       touch_lower_(0),
       touch_history_last_accepted_(0),
       touch_history_direction_(0),
       touch_min_major_(0),
       touch_max_major_(0),
       double_tap_focus_x_(0),
       double_tap_focus_y_(0),
       double_tap_mode_(DOUBLE_TAP_MODE_NONE),
       event_before_or_above_starting_gesture_event_(false) {
   DCHECK(listener_);
-  span_slop_ = (config.gesture_detector_config.touch_slop + kSlopEpsilon) * 2;
+  span_slop_ = config.span_slop + kSlopEpsilon;
   touch_min_major_ = config.min_scaling_touch_major;
   touch_max_major_ = std::min(config.min_scaling_span / std::sqrt(2.f),
                               2.f * touch_min_major_);
   min_span_ = config.min_scaling_span + kSlopEpsilon;
   ResetTouchHistory();
-  SetQuickScaleEnabled(config.quick_scale_enabled);
 }
 
 ScaleGestureDetector::~ScaleGestureDetector() {}
 
 bool ScaleGestureDetector::OnTouchEvent(const MotionEvent& event) {
   curr_time_ = event.GetEventTime();
 
   const int action = event.GetAction();
 
-  // Forward the event to check for double tap gesture.
-  if (quick_scale_enabled_) {
-    DCHECK(gesture_detector_);
-    gesture_detector_->OnTouchEvent(event);
-  }
-
   const bool stream_complete =
       action == MotionEvent::ACTION_UP ||
       action == MotionEvent::ACTION_CANCEL ||
       (action == MotionEvent::ACTION_POINTER_DOWN && InDoubleTapMode());
 
   if (action == MotionEvent::ACTION_DOWN || stream_complete) {
     // Reset any scale in progress with the listener.
     // If it's an ACTION_DOWN we're beginning a new event stream.
     // This means the app probably didn't give us all the events. Shame on it.
     if (in_progress_) {
@@ skipping 119 matching lines @@
       prev_span_x_ = curr_span_x_;
       prev_span_y_ = curr_span_y_;
       prev_span_ = curr_span_;
       prev_time_ = curr_time_;
     }
   }
 
   return true;
 }
 
-void ScaleGestureDetector::SetQuickScaleEnabled(bool scales) {
-  quick_scale_enabled_ = scales;
-  if (quick_scale_enabled_ && !gesture_detector_) {
-    gesture_detector_.reset(
-        new GestureDetector(config_.gesture_detector_config, this, this));
-  }
-}
-
-bool ScaleGestureDetector::IsQuickScaleEnabled() const {
-  return quick_scale_enabled_;
-}
-
 bool ScaleGestureDetector::IsInProgress() const { return in_progress_; }
 
 bool ScaleGestureDetector::InDoubleTapMode() const {
   return double_tap_mode_ == DOUBLE_TAP_MODE_IN_PROGRESS;
 }
 
 float ScaleGestureDetector::GetFocusX() const { return focus_x_; }
 
 float ScaleGestureDetector::GetFocusY() const { return focus_y_; }
 
@@ skipping 112 matching lines @@
   touch_history_last_accepted_time_ = base::TimeTicks();
 }
 
 void ScaleGestureDetector::ResetScaleWithSpan(float span) {
   in_progress_ = false;
   initial_span_ = span;
   double_tap_mode_ = DOUBLE_TAP_MODE_NONE;
 }
 
 }  // namespace ui