gtk-container-add (container widget)

container -- a gtk-container widget
widget -- a gtk-widget child widget to be placed inside container

Adds a child widget to the container. Typically used for simple containers such as gtk-window, gtk-frame, or gtk-button widgets.

For more complicated layout containers such as gtk-box or gtk-grid widgets, this function will pick default packing parameters that may not be correct. So consider functions such as the gtk-box-pack-start and gtk-grid-attach functions as an alternative to the gtk-container-add function in those cases.

A widget may be added to only one container at a time. You cannot place the same widget inside two different containers.