gtk: document callback return values as opaque pointers

gtk/gtkcolorsel.c

@@ -2899,7 +2899,7 @@ gtk_color_selection_set_change_palette_hook (GtkColorSelectionChangePaletteFunc
  * the new palette contents, and update the GtkSettings property
  * "gtk-color-palette" so all GtkColorSelection widgets will be modified.
  *
- * Return value: the previous change palette hook (that was replaced).
+ * Return value: (type gpointer) (transfer none): the previous change palette hook (that was replaced).
  *
  * Since: 2.2
  **/

gtk/gtkcombobox.c

@@ -6099,7 +6099,7 @@ gtk_combo_box_get_popup_accessible (GtkComboBox *combo_box)
  *
  * Returns the current row separator function.
  *
- * Return value: the current row separator function.
+ * Return value: (type gpointer) (transfer none): the current row separator function.
  *
  * Since: 2.6
  */

gtk/gtktreeview.c

@@ -14038,7 +14038,7 @@ gtk_tree_view_set_search_column (GtkTreeView *tree_view,
  *
  * Returns the compare function currently in use.
  *
- * Return value: the currently used compare function for the search code.
+ * Return value: (type gpointer) (transfer none): the currently used compare function for the search code.
  */
 
 GtkTreeViewSearchEqualFunc
@@ -14205,7 +14205,7 @@ gtk_tree_view_set_search_position_func (GtkTreeView                   *tree_view
  *
  * Returns the positioning function currently in use.
  *
- * Return value: the currently used function for positioning the search dialog.
+ * Return value: (type gpointer) (transfer none): the currently used function for positioning the search dialog.
  *
  * Since: 2.10
  */
@@ -15100,7 +15100,7 @@ gtk_tree_view_is_rubber_banding_active (GtkTreeView *tree_view)
  *
  * Returns the current row separator function.
  *
- * Return value: the current row separator function.
+ * Return value: (type gpointer) (transfer none): the current row separator function.
  *
  * Since: 2.6
  **/