Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!natinst!brian
From: brian@natinst.com (Brian H. Powell)
Newsgroups: comp.windows.x
Subject: GXinvert & planes
Message-ID: <17226@natinst.natinst.com>
Date: 11 Dec 90 15:50:37 GMT
Organization: National Instruments, Austin, TX
Lines: 15


     I was trying to invert some text (drawn with Xlib) to show a selection.
At first, I made a GC with a function of GXinvert, and a plane_mask of the
default AllPlanes.  This worked fine under OpenWindows, but failed under
the Sun MIT server (it drew all black).
     I went looking for some sample client code, and found a couple of
different examples where the plane_mask was set to the exclusive-or of the
foreground and background colors.  I tried this, and it worked.  But I didn't
understand why.  Perhaps it's because I'm not a color guru.
     Can somebody mail me an explanation of why it's done this way?  Thanks.

Brian H. Powell, M/S 56-14			National Instruments Corp.
	brian@natinst.com			6504 Bridge Point Parkway
	uunet!cs.utexas.edu!natinst!brian	Austin, Texas 78730-5039
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