Xlib voodoo XWidthOfScreen, etc

[Jeremy Huddleston]

I'm having some trouble understanding some of Xlib...

After changing resolution with RandR, all the following seem to report the new resolution properly:

$ xdpyinfo
$ xwininfo -root
$ xrandr
XineramaQueryScreens() called within my WM

however, XWidthOfScreen() and XHeightOfScreen() called from within my WM still report the old resolution.

I was under the impression that the internals of Display and Screen were updated "automagically" within Xlib.  Do I need to do something to force the internals to update?