-gchar *gis_prefs_get_string_v (GisPrefs *prefs, const gchar *group, const gchar *key);
-gboolean gis_prefs_get_boolean_v(GisPrefs *prefs, const gchar *group, const gchar *key);
-gint gis_prefs_get_integer_v(GisPrefs *prefs, const gchar *group, const gchar *key);
-gdouble gis_prefs_get_double_v (GisPrefs *prefs, const gchar *group, const gchar *key);
+gchar *gis_prefs_get_string_v (GisPrefs *prefs, const gchar *group, const gchar *key, GError **error);
+gboolean gis_prefs_get_boolean_v(GisPrefs *prefs, const gchar *group, const gchar *key, GError **error);
+gint gis_prefs_get_integer_v(GisPrefs *prefs, const gchar *group, const gchar *key, GError **error);
+gdouble gis_prefs_get_double_v (GisPrefs *prefs, const gchar *group, const gchar *key, GError **error);