gtk-widget-preferred-width-for-height (widget height)

widget -- a gtk-widget object
height -- an integer with the height which is available for allocation

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

Retrieves a minimum and natural width of the widget if it would be given the specified height.

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.