[clutter/clutter-1.22] device-manager-xi2: Fix core pointer retrieval race

[Emmanuele Bassi <ebassi src gnome org>]

commit 1be019852f0a64188df3d4e45820246f21fdacbe
Author: Sjoerd Simons <sjoerd simons collabora co uk>
Date:   Mon Dec 15 17:29:52 2014 +0000

    device-manager-xi2: Fix core pointer retrieval race
    
    The core pointer concept doesn't really exist anymore in an XI2 world,
    so the clutter API is a bit of a mismatch with what X provides. Using
    XIGetClientPointer doesn't really help, as far as i can tell the
    semantics of XIGetClientPointer are essentially: Whatever the X server
    picked when it had to reply with device-dependant data to a query
    without a device specifier. Not very useful...
    
    To make matters worse, whether XIGetClientPointer returns a valid
    pointer depends on whether there has been a query that forced it to pick
    one in the first place, making the whole thing pretty non-deterministic.
    
    This patch changes things around such that instead of using
    XIGetClientPointer to determine the core pointer, we simply pick the
    first master pointer device. In practise this will essentially always
    be the X virtual core pointer.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=729462

 clutter/x11/clutter-device-manager-xi2.c |   41 ++++++++++++-----------------
 clutter/x11/clutter-device-manager-xi2.h |    2 -
 2 files changed, 17 insertions(+), 26 deletions(-)
---
diff --git a/clutter/x11/clutter-device-manager-xi2.c b/clutter/x11/clutter-device-manager-xi2.c
index 769463b..223e875 100644
--- a/clutter/x11/clutter-device-manager-xi2.c
+++ b/clutter/x11/clutter-device-manager-xi2.c
@@ -222,21 +222,6 @@ is_touch_device (XIAnyClassInfo         **classes,
   return FALSE;
 }
 
-static void
-update_client_pointer (ClutterDeviceManagerXI2 *manager_xi2)
-{
-  ClutterBackendX11 *backend_x11;
-  int device_id;
-
-  backend_x11 =
-    CLUTTER_BACKEND_X11 (_clutter_device_manager_get_backend (CLUTTER_DEVICE_MANAGER (manager_xi2)));
-
-  XIGetClientPointer (backend_x11->xdpy, None, &device_id);
-
-  manager_xi2->client_pointer = g_hash_table_lookup (manager_xi2->devices_by_id,
-                                                     GINT_TO_POINTER (device_id));
-}
-
 static ClutterInputDevice *
 create_device (ClutterDeviceManagerXI2 *manager_xi2,
                ClutterBackendX11       *backend_x11,
@@ -816,7 +801,6 @@ clutter_device_manager_xi2_translate_event (ClutterEventTranslator *translator,
         XIHierarchyEvent *xev = (XIHierarchyEvent *) xi_event;
 
         translate_hierarchy_event (backend_x11, manager_xi2, xev);
-        update_client_pointer (manager_xi2);
       }
       retval = CLUTTER_TRANSLATE_REMOVE;
       break;
@@ -840,8 +824,6 @@ clutter_device_manager_xi2_translate_event (ClutterEventTranslator *translator,
 
         if (source_device)
           _clutter_input_device_reset_scroll_info (source_device);
-
-        update_client_pointer (manager_xi2);
       }
       retval = CLUTTER_TRANSLATE_REMOVE;
       break;
@@ -1391,17 +1373,29 @@ clutter_device_manager_xi2_get_core_device (ClutterDeviceManager   *manager,
                                             ClutterInputDeviceType  device_type)
 {
   ClutterDeviceManagerXI2 *manager_xi2 = CLUTTER_DEVICE_MANAGER_XI2 (manager);
+  ClutterInputDevice *pointer = NULL;
+  GList *l;
+
+  for (l = manager_xi2->master_devices; l != NULL ; l = l->next)
+    {
+      ClutterInputDevice *device = l->data;
+      if (clutter_input_device_get_device_type (device) == CLUTTER_POINTER_DEVICE)
+        {
+          pointer = device;
+          break;
+        }
+    }
+
+  if (pointer == NULL)
+    return NULL;
 
   switch (device_type)
     {
     case CLUTTER_POINTER_DEVICE:
-      if (manager_xi2->client_pointer == NULL)
-        update_client_pointer (manager_xi2);
-
-      return manager_xi2->client_pointer;
+      return pointer;
 
     case CLUTTER_KEYBOARD_DEVICE:
-      return clutter_input_device_get_associated_device (manager_xi2->client_pointer);
+      return clutter_input_device_get_associated_device (pointer);
 
     default:
       break;
@@ -1505,7 +1499,6 @@ clutter_device_manager_xi2_constructed (GObject *gobject)
                                             &event_mask);
 
   XSync (backend_x11->xdpy, False);
-  update_client_pointer (manager_xi2);
 
   if (G_OBJECT_CLASS (clutter_device_manager_xi2_parent_class)->constructed)
     G_OBJECT_CLASS (clutter_device_manager_xi2_parent_class)->constructed (gobject);
diff --git a/clutter/x11/clutter-device-manager-xi2.h b/clutter/x11/clutter-device-manager-xi2.h
index ec54cbd..2ceb623 100644
--- a/clutter/x11/clutter-device-manager-xi2.h
+++ b/clutter/x11/clutter-device-manager-xi2.h
@@ -49,8 +49,6 @@ struct _ClutterDeviceManagerXI2
   GList *master_devices;
   GList *slave_devices;
 
-  ClutterInputDevice *client_pointer;
-
   int opcode;
 };