Retrieves the minimum and natural size of a widget, taking into account the widget’s preference for height-for-width management.
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 `GtkFixed`.
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.
Use [id@gtk_widget_measure] if you want to support baseline alignment.
a `GtkWidget` instance
location for storing the minimum size, or null
location for storing the natural size, or null