Gtk.Box.prototype.pack_end

function pack_end(child:Gtk.Widget, expand:Boolean, fill:Boolean, padding:Number):void {
    // Gjs wrapper for gtk_box_pack_end()
}

Adds child to box, packed with reference to the end of box. The child is packed after (away from end of) any other child packed with reference to the end of box.

child: the Gtk.Widget to be added to box
expand: true if the new child is to be given extra space allocated to box. The extra space will be divided evenly between all children of box that use this option
fill: true if space given to child by the expand option is actually allocated to child, rather than just padding it. This parameter has no effect if expand is set to false. A child is always allocated the full height of a horizontal Gtk.Box and the full width of a vertical Gtk.Box. This option affects the other dimension
padding: extra space in pixels to put between this child and its neighbors, over and above the global amount specified by Gtk.spacing property. If child is a widget at one of the reference ends of box, then padding pixels are also put between child and the reference edge of box