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>
 
 #include "base/logging.h"
 #include "base/utf_string_conversions.h"
 #include "ui/base/keycodes/keyboard_code_conversion_x.h"
 #include "ui/base/touch/touch_factory.h"
 #include "views/widget/root_view.h"
 
 namespace views {
 
 namespace {
 
 int GetTouchIDFromXEvent(XEvent* xev) {
-  float id = 0;
+  float slot = 0;
+  ui::TouchFactory* factory = ui::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.
-  ui::TouchFactory::TouchParam tp = ui::TouchFactory::TP_TRACKING_ID;
+  float tracking_id;
+  if (!factory->ExtractTouchParam(
+         *xev, ui::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
-  ui::TouchFactory::TouchParam tp = ui::TouchFactory::TP_SLOT_ID;
+  if (!factory->ExtractTouchParam(
+         *xev, ui::TouchFactory::TP_SLOT_ID, &slot))
+    LOG(ERROR) << "Could not get the slot ID for the event. Using 0.";
 #endif
-  if (!ui::TouchFactory::GetInstance()->ExtractTouchParam(*xev, tp, &id))
-    LOG(ERROR) << "Could not get the touch ID for the event. Using 0.";
-  return id;
+  return slot;
 }
 
 uint16 GetCharacterFromXKeyEvent(XKeyEvent* key) {
   char buf[6];
   int bytes_written = XLookupString(key, buf, 6, NULL, NULL);
   DCHECK_LE(bytes_written, 6);
 
   string16 result;
   return (bytes_written > 0 && UTF8ToUTF16(buf, bytes_written, &result) &&
           result.length() == 1) ? result[0] : 0;
@@ skipping 120 matching lines @@
       radius_x_(GetTouchParamFromXEvent(native_event,
                                         ui::TouchFactory::TP_TOUCH_MAJOR,
                                         2.0) / 2.0),
       radius_y_(GetTouchParamFromXEvent(native_event,
                                         ui::TouchFactory::TP_TOUCH_MINOR,
                                         2.0) / 2.0),
       rotation_angle_(GetTouchParamFromXEvent(native_event,
                                               ui::TouchFactory::TP_ORIENTATION,
                                               0.0)),
       force_(GetTouchForceFromXEvent(native_event)) {
-#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.
+    ui::TouchFactory* factory = ui::TouchFactory::GetInstance();
+    float tracking_id;
+    if (factory->ExtractTouchParam(*native_event,
+                                   ui::TouchFactory::TP_TRACKING_ID,
+                                   &tracking_id)) {
+      factory->ReleaseSlotForTrackingID(tracking_id);
+    }
+  }
+#else
   if (type() == ui::ET_TOUCH_PRESSED || type() == ui::ET_TOUCH_RELEASED) {
     ui::TouchFactory* factory = ui::TouchFactory::GetInstance();
     float slot;
     if (factory->ExtractTouchParam(*native_event,
                                    ui::TouchFactory::TP_SLOT_ID, &slot)) {
       factory->SetSlotUsed(slot, type() == ui::ET_TOUCH_PRESSED);
     }
   }
 #endif
 }
 
 }  // namespace views