gtk/gtk.go
func (v *ProgressBar) SetFraction(fraction float64) {
	C.gtk_progress_bar_set_fraction(v.native(), C.gdouble(fraction))
}
func (v *ProgressBar) SetFraction(fraction float64) {
	C.gtk_progress_bar_set_fraction(v.native(), C.gdouble(fraction))
}
// SetFraction() is a wrapper around gtk_progress_bar_set_fraction().