IconSource.setDirectionWildcarded

If the text direction is wildcarded, this source can be used as the base image for an icon in any #GtkTextDirection. If the text direction is not wildcarded, then the text direction the icon source applies to should be set with [gtk.icon_source.IconSource.setDirection], and the icon source will only be used with that text direction.

#GtkIconSet prefers non-wildcarded sources (exact matches) over wildcarded sources, and will use an exact match when possible.