See gtk_source_view_set_mark_category_tooltip_func() for more information. Since 2.8
a mark category.
a GtkSourceViewMarkTooltipFunc or NULL.
user data which will be passed to func.
a function to free the memory allocated for user_data or NULL if you do not want to supply such a function.
See Implementation
See gtk_source_view_set_mark_category_tooltip_func() for more information. Since 2.8