gtk:widget-insert-before (widget parent next)

widget -- a gtk:widget object
parent -- a gtk:widget object for the parent widget to insert widget into
next -- a gtk:widget object for the next sibling of widget or nil

Inserts widget into the child widget list of parent. It will be placed before next, or at the end if next is nil.

After calling this function, the gtk:widget-next-sibling function will return next. If parent is already set as the parent widget of widget, this function can also be used to reorder widget in the child widget list of parent.

This API is primarily meant for widget implementations. If you are just using a widget, you must use its own API for adding children.