Path: utzoo!attcan!uunet!cs.utexas.edu!tut.cis.ohio-state.edu!bloom-beacon!EXPO.LCS.MIT.EDU!jim
From: jim@EXPO.LCS.MIT.EDU (Jim Fulton)
Newsgroups: comp.windows.x
Subject: Re: Determining color/black-white
Message-ID: <8906231943.AA10184@expo.lcs.mit.edu>
Date: 23 Jun 89 19:43:11 GMT
References: <8906231926.AA12265@apple-gunkies.ai.mit.edu>
Sender: daemon@bloom-beacon.MIT.EDU
Organization: X Consortium, MIT Laboratory for Computer Science
Lines: 22


	What is the best method of determining if a screen supports color 
	or not?

Walk down the visuals of the screen using XGetVisualInfo.  There is an example
of how this routine is called in the client xdpyinfo.  Or, you could use 
XMatchVisualInfo to do the searching.  See Rosenthal and Lemke's paper 
"Visualizing X11 Clients" available through anonymous ftp from expo.lcs.mit.edu
as /contrib/Visuals.shar.


	DisplayCells doesn't work,

It tells you how many cells are in the colormap of the default visual.  If
the default visual is single-plane StaticGray or GrayScale, then you'll miss
out if there are other visuals available.


	checking number of planes seems to be a reasonable test.

Depends on whether or not you consider multiple shades of gray to be 
"colors" (i.e. think of displays with StaticGray or GrayScale visuals).