public virtual void get_preferred_width (out int minimum_width, out int natural_width)
Retrieves a widget’s initial minimum and natural width.
This call is specific to height-for-width requests.
The returned request will be modified by the GtkWidgetClass:
GtkWidget:adjust_size_request virtual method and by any
SizeGroups 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.
a Widget instance
location to store the minimum width, or null
location to store the natural width, or null