Gtk.Range.prototype.set_increments

function set_increments(step:Number, page:Number):void {
    // Gjs wrapper for gtk_range_set_increments()
}

Sets the step and page sizes for the range. The step size is used when the user clicks the Gtk.Scrollbar arrows or moves Gtk.Scale via arrow keys. The page size is used for example when moving via Page Up or Page Down keys.