gobject: add 'explicit notify' GParamSpec flag

Add a flag to prevent the automatic emission of the "notify" signal
during g_object_set_property().

If this flag is set then the class must explicitly emit the notify
for themselves.  This is already standard practice on most classes, but
we cannot simply remove the existing behaviour because there are surely
many cases where it is needed.

https://bugzilla.gnome.org/show_bug.cgi?id=731200

diff --git a/gobject/gobject.c b/gobject/gobject.c
index 4a35cd065b350b9817197a1eb66045a165c86d84..7e9e467529b4fce83bcde8fea91d4e1be0d814ee 100644 (file)
--- a/gobject/gobject.c
+++ b/gobject/gobject.c
@@ -1380,14 +1380,17 @@ object_set_property (GObject             *object,
     }
   else
     {
-      GParamSpec *notify_pspec;
-
       class->set_property (object, param_id, &tmp_value, pspec);
 
-      notify_pspec = get_notify_pspec (pspec);
+      if (~pspec->flags & G_PARAM_EXPLICIT_NOTIFY)
+        {
+          GParamSpec *notify_pspec;
+
+          notify_pspec = get_notify_pspec (pspec);
 
-      if (notify_pspec != NULL)
-        g_object_notify_queue_add (object, nqueue, notify_pspec);
+          if (notify_pspec != NULL)
+            g_object_notify_queue_add (object, nqueue, notify_pspec);
+        }
     }
   g_value_unset (&tmp_value);
 }

diff --git a/gobject/gparam.h b/gobject/gparam.h
index fb21f7bae6318246a51b0923be9ebeef5bbf3da0..8f216e4ceceb917edca49ebdfaa549058327a8f0 100644 (file)
--- a/gobject/gparam.h
+++ b/gobject/gparam.h
@@ -130,6 +130,10 @@ G_BEGIN_DECLS
  *  parameter is guaranteed to remain valid and 
  *  unmodified for the lifetime of the parameter. 
  *  Since 2.8
+ * @G_PARAM_EXPLICIT_NOTIFY: calls to g_object_set_property() for this
+ *   property will not automatically result in a "notify" signal being
+ *   emitted: the implementation must call g_object_notify() themselves
+ *   in case the property actually changes.  Since: 2.42.
  * @G_PARAM_PRIVATE: internal
  * @G_PARAM_DEPRECATED: the parameter is deprecated and will be removed
  *  in a future version. A warning will be generated if it is used
@@ -153,6 +157,7 @@ typedef enum
 #endif
   G_PARAM_STATIC_NICK        = 1 << 6,
   G_PARAM_STATIC_BLURB       = 1 << 7,
+  G_PARAM_EXPLICIT_NOTIFY     = 1 << 8,
   /* User defined flags go up to 30 */
   G_PARAM_DEPRECATED          = 1 << 31
 } GParamFlags;