defaultFilter

The default filter, that is, the filter that is initially active in the file chooser dialog.

If the default filter is null, the first filter of property@Gtk.FileDialog:filters is used as the default filter. If that property contains no filter, the dialog will be unfiltered.

If property@Gtk.FileDialog:filters is not null, the default filter should be part of the list. If it is not, the dialog may choose to not make it available.