Implementing the dispatch of the swipe gesture for one-finger touch swipes.

ui/events/gesture_detection/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.
 
 // MSVC++ requires this to be set before any other includes to get M_PI.
 #define _USE_MATH_DEFINES
 
 #include "ui/events/gesture_detection/gesture_detector.h"
 
 #include <cmath>
@@ skipping 254 matching lines @@
         if (dot < 0) {
           vx_total = 0;
           vy_total = 0;
           velocity_tracker_.Clear();
           break;
         }
         vx_total += vx2;
         vy_total += vy2;
       }
 
-      if (swipe_enabled_ && (vx_total || vy_total)) {
-        float vx = vx_total / count;
-        float vy = vy_total / count;
-        float vx_abs = std::abs(vx);
-        float vy_abs = std::abs(vy);
-
-        if (vx_abs < min_swipe_velocity_)
-          vx_abs = vx = 0;
-        if (vy_abs < min_swipe_velocity_)
-          vy_abs = vy = 0;
-
-        // Note that the ratio will be 0 if both velocites are below the min.
-        float ratio = vx_abs > vy_abs ? vx_abs / std::max(vy_abs, 0.001f)
-                                      : vy_abs / std::max(vx_abs, 0.001f);
-        if (ratio > min_swipe_direction_component_ratio_) {
-          if (vx_abs > vy_abs)
-            vy = 0;
-          else
-            vx = 0;
-
-          handled = listener_->OnSwipe(*current_down_event_, ev, vx, vy);
-        }
-      }
+      handled = handleSwipeIfNeeded(ev, vx_total / count, vy_total / count);
 
       if (two_finger_tap_allowed_for_gesture_ && ev.GetPointerCount() == 2 &&
           (ev.GetEventTime() - secondary_pointer_down_event_->GetEventTime() <=
            two_finger_tap_timeout_)) {
         handled = listener_->OnTwoFingerTap(*current_down_event_, ev);
       }
       two_finger_tap_allowed_for_gesture_ = false;
     } break;
 
     case MotionEvent::ACTION_DOWN:
@@ skipping 118 matching lines @@
           const int pointer_id = ev.GetPointerId(0);
           velocity_tracker_.ComputeCurrentVelocity(1000, max_fling_velocity_);
           const float velocity_y = velocity_tracker_.GetYVelocity(pointer_id);
           const float velocity_x = velocity_tracker_.GetXVelocity(pointer_id);
 
           if ((std::abs(velocity_y) > min_fling_velocity_) ||
               (std::abs(velocity_x) > min_fling_velocity_)) {
             handled = listener_->OnFling(
                 *current_down_event_, ev, velocity_x, velocity_y);
           }
+
+          handled |= handleSwipeIfNeeded(ev, velocity_x, velocity_y);
         }
 
         previous_up_event_ = ev.Clone();
 
         velocity_tracker_.Clear();
         is_double_tapping_ = false;
         defer_confirm_single_tap_ = false;
         timeout_handler_->StopTimeout(SHOW_PRESS);
         timeout_handler_->StopTimeout(LONG_PRESS);
       }
@@ skipping 101 matching lines @@
 
   if (second_down.GetEventTime() - first_up.GetEventTime() >
       double_tap_timeout_)
     return false;
 
   const float delta_x = first_down.GetX() - second_down.GetX();
   const float delta_y = first_down.GetY() - second_down.GetY();
   return (delta_x * delta_x + delta_y * delta_y < double_tap_slop_square_);
 }
 
+bool GestureDetector::handleSwipeIfNeeded(const MotionEvent& up,
+                                          float vx,
+                                          float vy) {
+  if (!swipe_enabled_ || (!vx && !vy))
+    return false;
+  float vx_abs = std::abs(vx);
+  float vy_abs = std::abs(vy);
+
+  if (vx_abs < min_swipe_velocity_)
+    vx_abs = vx = 0;
+  if (vy_abs < min_swipe_velocity_)
+    vy_abs = vy = 0;
+
+  // Note that the ratio will be 0 if both velocites are below the min.
+  float ratio = vx_abs > vy_abs ? vx_abs / std::max(vy_abs, 0.001f)
+                                : vy_abs / std::max(vx_abs, 0.001f);
+
+  if (ratio > min_swipe_direction_component_ratio_) {

[jdduke (slow), 2014/05/26 21:19:42]

Nit: I would early out here in the unsatisfied case, i.e.,

if (ratio < min_swipe_direction_component_ratio_)
  return false;

...

(Note that the inequality strictness doesn't really matter, either way should
work).

[mfomitchev, 2014/05/26 22:07:14]

Done.

+    if (vx_abs > vy_abs)
+      vy = 0;
+    else
+      vx = 0;
+
+    return listener_->OnSwipe(*current_down_event_, up, vx, vy);
+  }
+  return false;
+}
+
 }  // namespace ui