Eager Gesture Recognition on Aura

ui/events/gestures/gesture_provider_aura.cc

Index: ui/events/gestures/gesture_provider_aura.cc
diff --git a/ui/events/gestures/gesture_provider_aura.cc b/ui/events/gestures/gesture_provider_aura.cc
index 7485cda70e9fad124277642a8c685ecd0f9f3648..bf2deb325f0d2305038ec5fe4c5def25a6335a8b 100644
--- a/ui/events/gestures/gesture_provider_aura.cc
+++ b/ui/events/gestures/gesture_provider_aura.cc
@@ -28,6 +28,17 @@ bool GestureProviderAura::OnTouchEvent(const TouchEvent& event) {
     if (event.touch_id() != pointer_state_.GetPointerId(i))
       continue;
     pointer_id_is_active = true;
+
+    // If this is a touchmove event, and it isn't different from the last
+    // event, ignore it.
+    if (event.type() == ET_TOUCH_MOVED &&
+        event.x() == pointer_state_.GetX(i) &&
+        event.y() == pointer_state_.GetY(i) &&
+        std::max(event.radius_x(), event.radius_y()) * 2 ==
+            pointer_state_.GetTouchMajor(i) &&
+        event.force() == pointer_state_.GetPressure(i)) {

[jdduke (slow), 2014/07/30 15:29:32]

How noisy are force/radius values compared to position? I'd rather we preserve
the logic we had in ui_events_helper.cc for now (only comparing the position),
and fold in the radius/pressure if we find that necessary in the future.

[tdresser, 2014/07/31 15:33:31]

The amount of noise depends entirely on the firmware configuration, but you're
right that there is frequently more noise in the radius and pressure.

It feels wrong to me to be artificially filtering out legitimate changes in
radius and pressure though. If we feel the signal is too noisy, maybe we should
be smoothing it?

That being said, I don't care particularly strongly about it, if you'd prefer
only looking at location, that's fine.

[jdduke (slow), 2014/07/31 16:19:02]

It's not that I feel strongly about it, more so that this patch introduces a
substantial behavior change, so the fewer additional differences we layer in,
the better.  We can always fix it in a follow-up patch, and you're probably
right that using the size here makes sense.

[tdresser, 2014/08/01 13:35:32]

Done.

+      return false;
+    }
     break;
   }