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

views/touchui/touch_factory.cc

Index: views/touchui/touch_factory.cc
diff --git a/views/touchui/touch_factory.cc b/views/touchui/touch_factory.cc
index 84db3ebd7340d95e07183e2902fa42e1f9c7b14c..f11b2463801b3b3675dcb693426f5ae100c1b1ff 100644
--- a/views/touchui/touch_factory.cc
+++ b/views/touchui/touch_factory.cc
@@ -129,10 +129,11 @@ TouchFactory::TouchFactory()
       keep_mouse_cursor_(false),
       cursor_timer_(),
       pointer_device_lookup_(),
+      touch_device_list_(),
 #if defined(USE_XI2_MT)
-      touch_device_list_() {
+      slots_used_(),

[sadrul, 2011/09/19 16:13:36]

slots_used_ is used even when USE_XI2_MT is not set, right?

[ningxin.hu, 2011/09/20 16:08:49]

Yes.

+      tracking_id_map_() {
 #else
-      touch_device_list_(),
       slots_used_() {
 #endif
 #if defined(TOUCH_UI)
@@ -319,7 +320,32 @@ bool TouchFactory::IsTouchDevice(unsigned deviceid) const {
       touch_device_lookup_[deviceid] : false;
 }
 
-#if !defined(USE_XI2_MT)
+#if defined(USE_XI2_MT)
+int TouchFactory::AllocateSlotIdForTrackingId(uint32 tracking_id) {
+  TrackingIdMap::iterator itr = tracking_id_map_.find(tracking_id);
+  if (itr != tracking_id_map_.end())
+    return itr->second;
+
+  // Find the lowest available slot, assume kMaxTouchPoints is less than 32
+  int slot = ffs(~(slots_used_.to_ulong())) - 1;

[sadrul, 2011/09/19 16:13:36]

I think we can spare a few cycles here and do a loop to find an available slot
instead!

[ningxin.hu, 2011/09/20 16:08:49]

OK. Will implement it.

+  if (slot == -1) {
+    LOG(ERROR) << "Could not find available slot for touch point";
+    return 0;
+  }
+  SetSlotUsed(slot, true);
+  tracking_id_map_.insert(std::make_pair(tracking_id, slot));
+  return slot;
+}
+
+void TouchFactory::ReleaseSlotIdForTrackingId(uint32 tracking_id) {
+  TrackingIdMap::iterator itr = tracking_id_map_.find(tracking_id);
+  if (itr != tracking_id_map_.end()) {
+    SetSlotUsed(itr->second, false);
+    tracking_id_map_.erase(itr);
+  }

[sadrul, 2011/09/19 16:13:36]

Add a NOTREACHED or DCHECK on else

[ningxin.hu, 2011/09/20 16:08:49]

Will add. Thanks for comment.

+}
+#endif
+
 bool TouchFactory::IsSlotUsed(int slot) const {
   CHECK_LT(slot, kMaxTouchPoints);
   return slots_used_[slot];
@@ -329,7 +355,6 @@ void TouchFactory::SetSlotUsed(int slot, bool used) {
   CHECK_LT(slot, kMaxTouchPoints);
   slots_used_[slot] = used;
 }
-#endif
 
 bool TouchFactory::GrabTouchDevices(Display* display, ::Window window) {
 #if defined(TOUCH_UI)