Touch Events - changedTouches list includes non-changed touch points on Android

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/debug/trace_event.h"
 #include "base/stl_util.h"
 #include "content/browser/renderer_host/input/timeout_monitor.h"
@@ skipping 685 matching lines @@
 }
 
 scoped_ptr<CoalescedWebTouchEvent> TouchEventQueue::PopTouchEvent() {
   DCHECK(!touch_queue_.empty());
   scoped_ptr<CoalescedWebTouchEvent> event(touch_queue_.front());
   touch_queue_.pop_front();
   return event.Pass();
 }
 
 void TouchEventQueue::SendTouchEventImmediately(
-    const TouchEventWithLatencyInfo& touch) {
+    TouchEventWithLatencyInfo& touch) {

[jdduke (slow), 2014/12/15 16:51:08]

Nit: Either pass by const ref, or by pointer (the latter for cases when the
argument is modified).

[USE s.singapati at gmail.com, 2014/12/17 11:28:43]

Done.

   if (needs_async_touchmove_for_outer_slop_region_) {
     // Any event other than a touchmove (e.g., touchcancel or secondary
     // touchstart) after a scroll has started will interrupt the need to send a
     // an outer slop-region exceeding touchmove.
     if (touch.event.type != WebInputEvent::TouchMove ||
         OutsideApplicationSlopRegion(touch.event,
                                      touch_sequence_start_position_))
       needs_async_touchmove_for_outer_slop_region_ = false;
   }
 
+  // For touchmove events, compare touch points position from current event
+  // to last sent event and update touch points state.
+  if (touch.event.type == WebInputEvent::TouchMove) {
+    if (last_sent_touchmove_) {
+      for (unsigned int i = 0; i < last_sent_touchmove_->touchesLength; ++i) {
+        const WebTouchPoint& last_touchmove_point =
+            last_sent_touchmove_->touches[i];
+
+        // touches with same id may not have same index in touches array
+        for (unsigned int j = 0; j < touch.event.touchesLength; ++j) {
+          WebTouchPoint& current_touchmove_point = touch.event.touches[j];
+          if (last_touchmove_point.id == current_touchmove_point.id) {
+            if (fabs(current_touchmove_point.position.x -

[jdduke (slow), 2014/12/15 16:51:08]

Can we avoid using the epsilon? If the touch really hasn't been updated, the
position should match precisely, I think.

[USE s.singapati at gmail.com, 2014/12/17 11:28:43]

Done. Did more testing and no problems found.

+                last_touchmove_point.position.x) < 0.000001
+                && fabs(current_touchmove_point.position.y -
+                    last_touchmove_point.position.y) < 0.000001)
+              current_touchmove_point.state = WebTouchPoint::StateStationary;
+
+            break;
+          }
+        }
+      }
+      *last_sent_touchmove_ = touch.event;
+    } else {
+      last_sent_touchmove_.reset(new WebTouchEvent(touch.event));
+    }
+  } else {
+    if (last_sent_touchmove_)

[jdduke (slow), 2014/12/15 16:51:08]

Nit: No need for the if, you can just unconditionally reset the scoped_ptr.

[USE s.singapati at gmail.com, 2014/12/17 11:28:42]

Done.

+      last_sent_touchmove_.reset();
+  }
+
   client_->SendTouchEventImmediately(touch);
 }
 
 TouchEventQueue::PreFilterResult
 TouchEventQueue::FilterBeforeForwarding(const WebTouchEvent& event) {
   if (timeout_handler_ && timeout_handler_->FilterEvent(event))
     return ACK_WITH_NO_CONSUMER_EXISTS;
 
   if (touchmove_slop_suppressor_->FilterEvent(event))
     return ACK_WITH_NOT_CONSUMED;
 
   if (WebTouchEventTraits::IsTouchSequenceStart(event)) {
     touch_consumer_states_.clear();
     send_touch_events_async_ = false;
     pending_async_touchmove_.reset();
+    last_sent_touchmove_.reset();
+
     touch_sequence_start_position_ = gfx::PointF(event.touches[0].position);
     drop_remaining_touches_in_sequence_ = false;
     if (!has_handlers_) {
       drop_remaining_touches_in_sequence_ = true;
       return ACK_WITH_NO_CONSUMER_EXISTS;
     }
   }
 
   if (drop_remaining_touches_in_sequence_ &&
       event.type != WebInputEvent::TouchCancel) {
@@ skipping 35 matching lines @@
         if (ack_result != INPUT_EVENT_ACK_STATE_NO_CONSUMER_EXISTS)
           touch_consumer_states_.mark_bit(point.id);
         else
           touch_consumer_states_.clear_bit(point.id);
       }
     }
   }
 }
 
 }  // namespace content