touchui: Convert XI2 MT tracking id to slot id for gesture recognizer

views/events/event_x.cc

Index: views/events/event_x.cc
diff --git a/views/events/event_x.cc b/views/events/event_x.cc
index fda4affb3038f172432e0f45dd3c2641d69a66f7..a014e2ee62113ea5b97643a684b13bb2795a04e8 100644
--- a/views/events/event_x.cc
+++ b/views/events/event_x.cc
@@ -122,18 +122,22 @@ ui::EventType GetTouchEventType(XEvent* xev) {
 }
 
 int GetTouchIDFromXEvent(XEvent* xev) {
-  float id = 0;
+  float slot = 0;

[Daniel Kurtz, 2011/09/24 01:53:36]

id is a better name, since it is used for both touchID and slotID

[sadrul, 2011/09/24 03:06:31]

I think 'slot' is fine. Right now, 'slot id' is essentially the same as 'touch
id'. For _MT, the we compute the 'slot id' from the 'tracking id'. For non-MT,
we already have the 'slot id' from X. Ideally, we would always compute the
'touch id' from the 'tracking id'. Once the code around this settles (there are
refactoring happening in this space), I will try to consolidate this code to
determine the touch-id (this should allow us to get rid of one of the cros
patches we carry).

 #if defined(USE_XI2_MT)
-  // TODO(ningxin.hu@gmail.com): Make the id always start from 0 for a new
-  // touch-sequence when TRACKING_ID is used to extract the touch id.
-  TouchFactory::TouchParam tp = TouchFactory::TP_TRACKING_ID;
+  float tracking_id;
+  TouchFactory* factory = TouchFactory::GetInstance();

[Daniel Kurtz, 2011/09/24 01:53:36]

Pull "TouchFactory*" and "return slot" out of the #ifdef block, and for
consistency, make the if() logic consistent.

[ningxin.hu, 2011/09/25 16:35:39]

Thanks. I will follow up.

+  if (factory->ExtractTouchParam(
+        *xev, TouchFactory::TP_TRACKING_ID, &tracking_id))
+    slot = factory->GetSlotForTrackingID(tracking_id);
+  else
+    LOG(ERROR) << "Could not get the touch ID for the event. Using 0.";
+  return slot;
 #else
-  TouchFactory::TouchParam tp = TouchFactory::TP_SLOT_ID;
-#endif
   if (!TouchFactory::GetInstance()->ExtractTouchParam(
-          *xev, tp, &id))
+         *xev, TouchFactory::TP_SLOT_ID, &slot))
     LOG(ERROR) << "Could not get the touch ID for the event. Using 0.";

[Daniel Kurtz, 2011/09/24 01:53:36]

Could not get the slot ID ...

[sadrul, 2011/09/24 03:06:31]

Ditto.

[ningxin.hu, 2011/09/25 16:35:39]

Thanks. Will correct.

-  return id;
+  return slot;
+#endif
 }
 
 ui::EventType EventTypeFromNative(NativeEvent2 native_event) {
@@ -424,7 +428,20 @@ TouchEvent::TouchEvent(NativeEvent2 native_event_2,
                                               TouchFactory::TP_ORIENTATION,
                                               0.0)),
       force_(GetTouchForceFromXEvent(native_event_2)) {
-#if !defined(USE_XI2_MT)
+#if defined(USE_XI2_MT)
+  if (type() == ui::ET_TOUCH_RELEASED) {
+    // NOTE: The slot is allocated by TouchFactory for each XI_TouchBegin
+    //       event, which carries a new tracking ID to identify a new touch
+    //       sequence.
+    TouchFactory* factory = TouchFactory::GetInstance();
+    float tracking_id;
+    if (factory->ExtractTouchParam(*native_event_2,
+                                   TouchFactory::TP_TRACKING_ID,
+                                   &tracking_id)) {
+      factory->ReleaseSlotForTrackingID(tracking_id);
+    }
+  }
+#else
   if (type() == ui::ET_TOUCH_PRESSED || type() == ui::ET_TOUCH_RELEASED) {
     TouchFactory* factory = TouchFactory::GetInstance();
     float slot;