[Android] Use DIP coordinates with MotionEventAndroid

content/browser/renderer_host/input/touch_event_queue.cc

 // Copyright 2013 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 "content/browser/renderer_host/input/touch_event_queue.h"
 
 #include "base/auto_reset.h"
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
 #include "base/stl_util.h"
 #include "content/browser/renderer_host/input/timeout_monitor.h"
 #include "content/browser/renderer_host/input/web_touch_event_traits.h"
 #include "content/public/common/content_switches.h"
 #include "ui/gfx/geometry/point_f.h"
 
 using blink::WebInputEvent;
 using blink::WebTouchEvent;
 using blink::WebTouchPoint;
 using ui::LatencyInfo;
 
 namespace content {
 namespace {
 
+// Using a small epsilon when comparing slop distances allows pixel perfect
+// slop determination when using fractional DIP coordinates (assuming the slop
+// region and DPI scale are reasonably proportioned).
+const float kSlopEpsilon = .05f;
+
 typedef std::vector<TouchEventWithLatencyInfo> WebTouchEventWithLatencyList;
 
 TouchEventWithLatencyInfo ObtainCancelEventForTouchEvent(
     const TouchEventWithLatencyInfo& event_to_cancel) {
   TouchEventWithLatencyInfo event = event_to_cancel;
   event.event.type = WebInputEvent::TouchCancel;
   for (size_t i = 0; i < event.event.touchesLength; i++)
     event.event.touches[i].state = WebTouchPoint::StateCancelled;
   return event;
 }
@@ skipping 126 matching lines @@
 
   // The event for which the ack timeout is triggered.
   TouchEventWithLatencyInfo timeout_event_;
 
   // Provides timeout-based callback behavior.
   TimeoutMonitor timeout_monitor_;
 };
 
 // Provides touchmove slop suppression for a single touch that remains within
 // a given slop region, unless the touchstart is preventDefault'ed.
+// TODO(jdduke): Use a flag bundled with each TouchEvent declaring whether it
+// has exceeded the slop region, removing duplicated slop determination logic.
 class TouchEventQueue::TouchMoveSlopSuppressor {
  public:
   TouchMoveSlopSuppressor(double slop_suppression_length_dips)
       : slop_suppression_length_dips_squared_(slop_suppression_length_dips *
                                               slop_suppression_length_dips),
         suppressing_touch_moves_(false) {}
 
   bool FilterEvent(const WebTouchEvent& event) {
     if (WebTouchEventTraits::IsTouchSequenceStart(event)) {
       touch_sequence_start_position_ =
@@ skipping 101 matching lines @@
 };
 
 TouchEventQueue::TouchEventQueue(TouchEventQueueClient* client,
                                  TouchScrollingMode mode,
                                  double touchmove_suppression_length_dips)
     : client_(client),
       dispatching_touch_ack_(NULL),
       dispatching_touch_(false),
       touch_filtering_state_(TOUCH_FILTERING_STATE_DEFAULT),
       ack_timeout_enabled_(false),
-      touchmove_slop_suppressor_(
-          new TouchMoveSlopSuppressor(touchmove_suppression_length_dips)),
+      touchmove_slop_suppressor_(new TouchMoveSlopSuppressor(
+          touchmove_suppression_length_dips + kSlopEpsilon)),
       absorbing_touch_moves_(false),
       touch_scrolling_mode_(mode) {
   DCHECK(client);
 }
 
 TouchEventQueue::~TouchEventQueue() {
   if (!touch_queue_.empty())
     STLDeleteElements(&touch_queue_);
 }
 
@@ skipping 325 matching lines @@
   } else if (event.type == WebInputEvent::TouchStart) {
     for (unsigned i = 0; i < event.touchesLength; ++i) {
       const WebTouchPoint& point = event.touches[i];
       if (point.state == WebTouchPoint::StatePressed)
         touch_ack_states_[point.id] = ack_result;
     }
   }
 }
 
 }  // namespace content