[glib/gdbus-codegen] gdbus-codegen: Never emit empty PropertiesChanged signals

[David Zeuthen <davidz src gnome org>]

commit a3fa748e54ec077a764a3045c92df59d00ba0edb
Author: David Zeuthen <davidz redhat com>
Date:   Fri Apr 15 16:11:43 2011 -0400

    gdbus-codegen: Never emit empty PropertiesChanged signals
    
    It's not that it's actually a bug to do so per se, strictly speaking,
    it's just pointless and wasteful.
    
    Signed-off-by: David Zeuthen <davidz redhat com>

 gio/gdbus-codegen/codegen.py |   28 +++++++++++++++++++---------
 1 files changed, 19 insertions(+), 9 deletions(-)
---
diff --git a/gio/gdbus-codegen/codegen.py b/gio/gdbus-codegen/codegen.py
index d86147d..67cf048 100644
--- a/gio/gdbus-codegen/codegen.py
+++ b/gio/gdbus-codegen/codegen.py
@@ -1705,9 +1705,10 @@ class CodeGenerator:
             self.c.write('  GList *l;\n'
                          '  GVariantBuilder builder;\n'
                          '  GVariantBuilder invalidated_builder;\n'
+                         '  guint num_changes;\n'
                          '  g_variant_builder_init (&builder, G_VARIANT_TYPE ("a{sv}"));\n'
                          '  g_variant_builder_init (&invalidated_builder, G_VARIANT_TYPE ("as"));\n'
-                         '  for (l = skeleton->priv->changed_properties; l != NULL; l = l->next)\n'
+                         '  for (l = skeleton->priv->changed_properties, num_changes = 0; l != NULL; l = l->next)\n'
                          '    {\n'
                          '      ChangedProperty *cp = l->data;\n'
                          '      GVariant *variant;\n'
@@ -1719,16 +1720,25 @@ class CodeGenerator:
                          '          variant = g_dbus_gvalue_to_gvariant (cur_value, G_VARIANT_TYPE (cp->info->parent_struct.signature));\n'
                          '          g_variant_builder_add (&builder, "{sv}", cp->info->parent_struct.name, variant);\n'
                          '          g_variant_unref (variant);\n'
+                         '          num_changes++;\n'
                          '        }\n'
                          '    }\n'
-                         '  g_dbus_connection_emit_signal (g_dbus_interface_skeleton_get_connection (G_DBUS_INTERFACE_SKELETON (skeleton)),\n'
-                         '                                 NULL, g_dbus_interface_skeleton_get_object_path (G_DBUS_INTERFACE_SKELETON (skeleton)),\n'
-                         '                                 "org.freedesktop.DBus.Properties",\n'
-                         '                                 "PropertiesChanged",\n'
-                         '                                 g_variant_new ("(sa{sv}as)",\n'
-                         '                                                "%s",\n'
-                         '                                                &builder, &invalidated_builder),\n'
-                         '                                 NULL);\n'
+                         '  if (num_changes > 0)\n'
+                         '    {\n'
+                         '      g_dbus_connection_emit_signal (g_dbus_interface_skeleton_get_connection (G_DBUS_INTERFACE_SKELETON (skeleton)),\n'
+                         '                                     NULL, g_dbus_interface_skeleton_get_object_path (G_DBUS_INTERFACE_SKELETON (skeleton)),\n'
+                         '                                     "org.freedesktop.DBus.Properties",\n'
+                         '                                     "PropertiesChanged",\n'
+                         '                                     g_variant_new ("(sa{sv}as)",\n'
+                         '                                                    "%s",\n'
+                         '                                                    &builder, &invalidated_builder),\n'
+                         '                                     NULL);\n'
+                         '    }\n'
+                         '  else\n'
+                         '    {\n'
+                         '      g_variant_builder_clear (&builder);\n'
+                         '      g_variant_builder_clear (&invalidated_builder);\n'
+                         '    }\n'
                          %(i.name))
             self.c.write('  g_list_foreach (skeleton->priv->changed_properties, (GFunc) _changed_property_free, NULL);\n')
             self.c.write('  g_list_free (skeleton->priv->changed_properties);\n')