File chooser interface used by GtkFileChooserWidget and gtkfilechooser.
This is an interface and cannot be instantiated directly.
GtkFileChooser is an interface that can be implemented by file
selection widgets. In GTK+, the main objects that implement this
interface are GtkFileChooserWidget,
and GtkFileChooserButton. You do not need to write
an object that implements the GtkFileChooser
interface unless you are trying to adapt an existing file selector
to expose a standard programming interface.