Re: face colors on 256 colors terminals

[Dan Nicolaescu <dann@ics.uci.edu>]

David Kastrup <dak@gnu.org> writes:

  > Dan Nicolaescu <dann@ics.uci.edu> writes:
  > 
  > > "Eli Zaretskii" <eliz@gnu.org> writes:
  > >
  > >   > > Cc: emacs-devel@gnu.org
  > >   > > From: Dan Nicolaescu <dann@ics.uci.edu>
  > >   > > Date: Wed, 06 Apr 2005 10:52:26 -0700
  > >   > > 
  > >   > > Agreed. The problem seems to be that tty-colors.el and color-name-rgb-alist
  > >   > > don't use the same of scaling. 
  > >   > > Do you want me to do check if rescaling the values in
  > >   > > color-name-rgb-alist gives good results?
  > >   > 
  > >   > Yes, please.
  > >
  > > I checked and I could not see any difference in behavior compared to the
  > > approach in my first patch.
  > >
  > > Is this OK? 
  > 
  > I am certain I am missing the context, but is this really related to
  > the #RRGGBB notation in any manner?  It really looks awful to me if
  > white gets defined as #ff00ff00ff00, so I'd like to be as bothersome
  > as to be grateful for some factual reassurance that we are indeed
  > catering here for a real instead of a perceived problem, and that the
  > fix in that manner is the right thing to do.

Well,  there patch has 3 parts. 

Part1:
The patch to xterm-register-default-colors changes the way the 8bit
R/G/B values are computed for a 256 color xterm to match what the
xterm currently does. This part should be correct and
non-controversial.

Part2:
xterm-rgb-convert-to-16bit converts an 8bit color value (say Y) to a 16bit
color. As we discussed, the result can either be Y0 or YY.
My empirical testing show that there's no visible difference between
the two. 
I have no opinion which is better, if any.
Eli seems to think that Y0 is the correct conversion, I don't have a
problem going with that. (although "esthetically" YY looks better).

Part3:
color-name-rgb-alist contains the colors in rgb.txt converted to
16bit. It should use the same conversion as
xterm-rgb-convert-to-16bit. So this part is only needed if the
conversion performed by xterm-rgb-convert-to-16bit is Y->Y0.
(Hmmm, if the Y->Y0 conversion is used then
pc-win.el:msdos-color-values needs to be changed in the same way). 

So when a final decision is made about using the YY or Y0 conversion I
can check in the corresponding patch.