Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!mailrus!cwjcc!tut.cis.ohio-state.edu!bloom-beacon!ATHENA.MIT.EDU!swick
From: swick@ATHENA.MIT.EDU (Ralph R. Swick)
Newsgroups: comp.windows.x
Subject: re: unexpose events?
Message-ID: <8812081608.AA02314@LYRE.MIT.EDU>
Date: 8 Dec 88 16:08:51 GMT
References: <7978@pasteur.Berkeley.EDU>
Sender: daemon@bloom-beacon.MIT.EDU
Organization: DEC/MIT Project Athena
Lines: 10

> I'm writing a program that spends a lot of time computing each pixel
> of a window.  What I would like to do is to have my program be informed
> when its window becomes obscured in a certain region so I don't have
> to waste computrons on unexposed window regions.

As rws pointed out, there is no direct (i.e. general) support in the
protocol for this, but some applications may be amenable to the following
hack:  to determine the (instantaneous) visible region(s) of a window,
or of a rectangular sub-region, while simultaneously destroying the
contents, map a subwindow across the area of interest, then unmap it and
process the resulting Exposures.