gtk:widget-preferred-height (widget)

widget -- a gtk:widget object

minimum-height -- an integer with the minimum height, or nil
natural-height -- an integer with the natural height, or nil

Retrieves an initial minimum and natural height of the widget. This call is specific to width-for-height requests.

The returned request will be modified by the GtkWidgetClass::adjust_size_request virtual method and by any gtk:size-group objects that have been applied. That is, the returned request is the one that should be used for layout, not necessarily the one returned by the widget itself.