proper way to get Shell widget resized calls?

CoreClassPart contains (XtWidgetProc)resize.

If I were to create my own widget, I could easily specify a Resize()
function to call simply by static assignment to the compiled value of my
widget's ClassRec.

However, I'd like to have a Resize function that gets called when the
application window resizes, without having to create a widget just to
have Resize() called.

What's a proper way to do that?

Outright setting (application)ShellClassRec.CoreClassPart.resize looks
like a bad idea: it's initially non-NULL by the time I'd consider
setting it and may do useful stuff I wouldn't want to skip by preempting
it with my Resize function.  I haven't investigated what
XawVendorShellExtResize does, though (but my application has no vendor
extensions of its own).  If nothing useful in my specific case, then
maybe preempting it isn't a problem, but doing so strikes me as very
likely the wrong answer given the way X normally works.  :)

Thanks in advance,
 -WBE