gtk-widget-preferred-size (widget)

widget -- a gtk-widget object

minimum-size -- a gtk-requisition instance with the minimum size, or nil
natural-size -- a gtk-requisition instance with the the natural size, or nil

Retrieves the minimum and natural size of a widget, taking into account the preference for height-for-width management of the widget.

This is used to retrieve a suitable size by container widgets which do not impose any restrictions on the child placement. It can be used to deduce toplevel window and menu sizes as well as child widgets in free-form containers such as gtk-layout widget. Handle with care. Note that the natural height of a height-for-width widget will generally be a smaller size than the minimum height, since the required height for the natural width is generally smaller than the required height for the minimum width.