[notify] add 'conditional' to _notify_queue_freeze

When the 'conditional' parameter is TRUE, the queue will only be frozen
(ie: have its freeze count increase by one) if it is already frozen.

This will allow us to avoid a freeze-notify-thaw in the case that we
just want to notify on a single property.

Another approach may have been to add an is_frozen() type call and avoid
even increasing the freeze count at all in this case.  Unfortunately,
I'm not totally sure what is the exact expected semantics of
simultaneous notifications in multiple threads and this may interact
badly with someone freezing or thawing in between our check and
emission.

diff --git a/gobject/gobject.c b/gobject/gobject.c
index 8c7f4ef..85cad66 100644 (file)
--- a/gobject/gobject.c
+++ b/gobject/gobject.c
@@ -222,7 +222,8 @@ g_object_notify_queue_free (gpointer data)
 }
 
 static inline GObjectNotifyQueue*
-g_object_notify_queue_freeze (GObject *object)
+g_object_notify_queue_freeze (GObject  *object,
+                              gboolean  conditional)
 {
   GObjectNotifyQueue *nqueue;
 
@@ -230,6 +231,12 @@ g_object_notify_queue_freeze (GObject *object)
   nqueue = g_datalist_id_get_data (&object->qdata, quark_notify_queue);
   if (!nqueue)
     {
+      if (conditional)
+        {
+          G_UNLOCK(notify_lock);
+          return NULL;
+        }
+
       nqueue = g_slice_new0 (GObjectNotifyQueue);
       g_datalist_id_set_data_full (&object->qdata, quark_notify_queue,
                                    nqueue, g_object_notify_queue_free);
@@ -927,7 +934,7 @@ g_object_init (GObject              *object,
   if (CLASS_HAS_PROPS (class))
     {
       /* freeze object's notification queue, g_object_newv() preserves pairedness */
-      g_object_notify_queue_freeze (object);
+      g_object_notify_queue_freeze (object, FALSE);
     }
 
   if (CLASS_HAS_CUSTOM_CONSTRUCTOR (class))
@@ -1057,7 +1064,7 @@ g_object_freeze_notify (GObject *object)
     return;
 
   g_object_ref (object);
-  g_object_notify_queue_freeze (object);
+  g_object_notify_queue_freeze (object, FALSE);
   g_object_unref (object);
 }
 
@@ -1090,7 +1097,7 @@ g_object_notify_by_spec_internal (GObject    *object,
 
   if (notify_pspec != NULL)
     {
-      nqueue = g_object_notify_queue_freeze (object);
+      nqueue = g_object_notify_queue_freeze (object, FALSE);
       g_object_notify_queue_add (object, nqueue, notify_pspec);
       g_object_notify_queue_thaw (object, nqueue);
     }
@@ -1221,7 +1228,7 @@ g_object_thaw_notify (GObject *object)
   /* FIXME: Freezing is the only way to get at the notify queue.
    * So we freeze once and then thaw twice.
    */
-  nqueue = g_object_notify_queue_freeze (object);
+  nqueue = g_object_notify_queue_freeze (object, FALSE);
   g_object_notify_queue_thaw (object, nqueue);
   g_object_notify_queue_thaw (object, nqueue);
 
@@ -1630,7 +1637,7 @@ g_object_newv (GType       object_type,
   if (CLASS_HAS_PROPS (class))
     {
       if (newly_constructed || n_oparams)
-       nqueue = g_object_notify_queue_freeze (object);
+       nqueue = g_object_notify_queue_freeze (object, FALSE);
       if (newly_constructed)
        g_object_notify_queue_thaw (object, nqueue);
     }
@@ -1750,7 +1757,7 @@ g_object_constructor (GType                  type,
   /* set construction parameters */
   if (n_construct_properties)
     {
-      GObjectNotifyQueue *nqueue = g_object_notify_queue_freeze (object);
+      GObjectNotifyQueue *nqueue = g_object_notify_queue_freeze (object, FALSE);
       
       /* set construct properties */
       while (n_construct_properties--)
@@ -1797,7 +1804,7 @@ g_object_set_valist (GObject       *object,
   g_return_if_fail (G_IS_OBJECT (object));
   
   g_object_ref (object);
-  nqueue = g_object_notify_queue_freeze (object);
+  nqueue = g_object_notify_queue_freeze (object, FALSE);
   
   name = first_property_name;
   while (name)
@@ -2025,7 +2032,7 @@ g_object_set_property (GObject        *object,
   g_return_if_fail (G_IS_VALUE (value));
   
   g_object_ref (object);
-  nqueue = g_object_notify_queue_freeze (object);
+  nqueue = g_object_notify_queue_freeze (object, FALSE);
   
   pspec = g_param_spec_pool_lookup (pspec_pool,
                                    property_name,