child to box, packed with reference to the start of box.
The child is packed after any other child packed with reference
to the start of box.gtkBoxPackStart(object, child, expand = TRUE, fill = TRUE, padding = 0)objectGtkBoxchildGtkWidget to be added to boxexpandTRUE 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 optionfillpadding"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