event-widget: factor out clock format function

This function will be used by other pieces of code later. We also gain
a tiny performance improvement, as only one GSetting is ever created.

src/gcal-event-widget.c

@@ -188,13 +188,9 @@ static void
 gcal_event_widget_init (GcalEventWidget *self)
 {
   GtkWidget *widget;
-  GSettings *settings;
-  gchar *clock_format;
 
   widget = GTK_WIDGET (self);
-  settings = g_settings_new ("org.gnome.desktop.interface");
-  clock_format = g_settings_get_string (settings, "clock-format");
-  self->clock_format_24h = g_strcmp0 (clock_format, "24h") == 0;
+  self->clock_format_24h = is_clock_format_24h ();
 
   gtk_widget_set_has_window (widget, FALSE);
   gtk_widget_set_can_focus (widget, TRUE);
@@ -207,9 +203,6 @@ gcal_event_widget_init (GcalEventWidget *self)
                        GDK_ACTION_COPY);
 
   gtk_drag_source_add_text_targets (widget);
-
-  g_clear_object (&settings);
-  g_free (clock_format);
 }
 
 static void

src/gcal-utils.c

@@ -561,6 +561,20 @@ get_end_of_week (icaltimetype *date)
   return week_end;
 }
 
+gboolean
+is_clock_format_24h (void)
+{
+  static GSettings *settings = NULL;
+  g_autofree gchar *clock_format = NULL;
+
+  if (!settings)
+    settings = g_settings_new ("org.gnome.desktop.interface");
+
+  clock_format = g_settings_get_string (settings, "clock-format");
+
+  return g_strcmp0 (clock_format, "24h") == 0;
+}
+
 /* Function to do a last minute fixup of the AM/PM stuff if the locale
  * and gettext haven't done it right. Most English speaking countries
  * except the USA use the 24 hour clock (UK, Australia etc). However

src/gcal-utils.h

@@ -105,6 +105,8 @@ GDateTime*      get_start_of_week                               (icaltimetype
 
 GDateTime*      get_end_of_week                                 (icaltimetype          *date);
 
+gboolean        is_clock_format_24h                             (void);
+
 /* code brought from evolution */
 gsize           e_strftime_fix_am_pm                            (gchar                 *str,
                                                                  gsize                  max,