apply
This function modifies the class@Gtk.TextTag properties that are related to the #GtkSourceStyle properties. Other class@Gtk.TextTag properties are left untouched.
If @style is non-null, applies @style to @tag.
If @style is null, the related *-set properties of class@Gtk.TextTag are set to false.
Parameters
tag
a #GtkTextTag to apply styles to.