
If I understand your problem correctly, you want to have a way to send
exposures to your manager widget when your app-specific code draws xlib
graphics on the window.

It sounds like you might want to send an exposure using
XSendEvent and specifying a region. If you know the region you need to
send the exposure, generally you have the bounding rectangle of the objects,
you can use XCreateRegion to create a region, XUnionRectWithRegion to add the
new object polygons to the region, and then either use the region
to clip your GC for the redraw or use XRectInRegion to test which of your
other objects need to be redrawn. Keeping in mind that the stacking order
of overlapping objects affects how they look.

Hope it helps

-- 
Brian Dealy                |301-572-8267| It not knowing where it's at  
dealy@kong.gsfc.nasa.gov   |            | that's important,it's knowing
!uunet!dftsrv!kong!dealy   |            | where it's not at...  B.Dylan