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

views/events/event_x.cc

 // Copyright (c) 2011 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 "views/events/event.h"
 
 #include <gdk/gdk.h>
 #include <gdk/gdkx.h>
 #include <X11/extensions/XInput2.h>
 #include <X11/Xlib.h>
@@ skipping 104 matching lines @@
   if (tracking == 0l) {
     // The touch point has been released.
     return ui::ET_TOUCH_RELEASED;
   }
 
   return ui::ET_TOUCH_MOVED;
 #endif  // defined(USE_XI2_MT)
 }
 
 int GetTouchIDFromXEvent(XEvent* xev) {
-  float id = 0;
+  float slot = 0;
+  TouchFactory* factory = TouchFactory::GetInstance();
 #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;
+  if (!factory->ExtractTouchParam(
+         *xev, TouchFactory::TP_TRACKING_ID, &tracking_id))
+    LOG(ERROR) << "Could not get the slot ID for the event. Using 0.";
+  else
+    slot = factory->GetSlotForTrackingID(tracking_id);
 #else
-  TouchFactory::TouchParam tp = TouchFactory::TP_SLOT_ID;
+  if (!factory->ExtractTouchParam(
+         *xev, TouchFactory::TP_SLOT_ID, &slot))
+    LOG(ERROR) << "Could not get the slot ID for the event. Using 0.";
 #endif
-  if (!TouchFactory::GetInstance()->ExtractTouchParam(
-          *xev, tp, &id))
-    LOG(ERROR) << "Could not get the touch ID for the event. Using 0.";
-  return id;
+  return slot;
 }
 
 ui::EventType EventTypeFromNative(NativeEvent2 native_event) {
   switch (native_event->type) {
     case KeyPress:
       return ui::ET_KEY_PRESSED;
     case KeyRelease:
       return ui::ET_KEY_RELEASED;
     case ButtonPress:
       if (native_event->xbutton.button == 4 ||
@@ skipping 270 matching lines @@
       radius_x_(GetTouchParamFromXEvent(native_event_2,
                                         TouchFactory::TP_TOUCH_MAJOR,
                                         2.0) / 2.0),
       radius_y_(GetTouchParamFromXEvent(native_event_2,
                                         TouchFactory::TP_TOUCH_MINOR,
                                         2.0) / 2.0),
       rotation_angle_(GetTouchParamFromXEvent(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;
     if (factory->ExtractTouchParam(*native_event_2,
                                    TouchFactory::TP_SLOT_ID, &slot)) {
       factory->SetSlotUsed(slot, type() == ui::ET_TOUCH_PRESSED);
     }
   }
 #endif
 }
 
 }  // namespace views