Add multi-finger swipe detection to GestureDetector

ui/events/gesture_detection/gesture_config_helper_aura.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/gesture_config_helper.h"
 
 #include "ui/events/gestures/gesture_configuration.h"
 #include "ui/gfx/screen.h"
 
 namespace ui {
 namespace {
 
 GestureDetector::Config DefaultGestureDetectorConfig() {
   GestureDetector::Config config;
 
   config.longpress_timeout = base::TimeDelta::FromMilliseconds(
       GestureConfiguration::long_press_time_in_seconds() * 1000.);
   config.showpress_timeout = base::TimeDelta::FromMilliseconds(
       GestureConfiguration::show_press_delay_in_ms());
   config.double_tap_timeout = base::TimeDelta::FromMilliseconds(
       GestureConfiguration::semi_long_press_time_in_seconds() * 1000.);
   config.touch_slop =
       GestureConfiguration::max_touch_move_in_pixels_for_click();
   config.double_tap_slop =
       GestureConfiguration::max_distance_between_taps_for_double_tap();
   config.minimum_fling_velocity =
       GestureConfiguration::min_scroll_velocity();
   config.maximum_fling_velocity =
       GestureConfiguration::fling_velocity_cap();
+  config.swipe_enabled = true;
+  config.minimum_swipe_velocity = GestureConfiguration::min_swipe_speed();
+  config.minimum_swipe_direction_ratio =

[tdresser, 2014/04/22 15:27:16]

This name isn't great, nor was the previous one.

We could rename it minimum_swipe_deviation_angle, and do a wee bit of trig?

Side note: we're caching these configuration values all over the place, which
will make getting about://gesture up and running with the unified GR a bit of a
pain. I'm not sure how we'll want to approach that.

[jdduke (slow), 2014/04/24 00:54:29]

Yeah that's better, though I'll probably cache the cotan(angle) value to get the
ratio when initializing the GestureDetector.

+      GestureConfiguration::max_swipe_deviation_ratio();
 
   return config;
 }
 
 ScaleGestureDetector::Config DefaultScaleGestureDetectorConfig() {
   ScaleGestureDetector::Config config;
 
   config.gesture_detector_config = DefaultGestureDetectorConfig();
   config.min_scaling_touch_major = GestureConfiguration::default_radius() * 2;
   config.min_scaling_span =
       GestureConfiguration::min_distance_for_pinch_scroll_in_pixels();
   return config;
 }
 
 }  // namespace
 
 GestureProvider::Config DefaultGestureProviderConfig() {
   GestureProvider::Config config;
   config.display = gfx::Screen::GetNativeScreen()->GetPrimaryDisplay();
   config.gesture_detector_config = DefaultGestureDetectorConfig();
   config.scale_gesture_detector_config = DefaultScaleGestureDetectorConfig();
   config.gesture_begin_end_types_enabled = true;
   return config;
 }
 
 }  // namespace ui