Re: xterm-256color and face colors

[Dan Nicolaescu]

Giorgos Keramidas <address@hidden> writes:

  > Hi all,
  > 
  > The version of Emacs I am currently running is ``GNU Emacs 23.1.90.1
  > (i386-unknown-freebsd9.0, GTK+ Version 2.18.4) of 2009-12-11 on kobe'',
  > built from a Git snapshot a couple of days ago.
  > 
  > A recent update to FreeBSD synchronized our termcap database entries for
  > "xterm*" terminals with the one in xterm's source distribution.  This
  > was the first step towards making Emacs really support more than 8 color
  > cells in xterm windows under FreeBSD.
  > 
  > Unfortunately this seems to have broken many face-colors that use X11
  > names in their face attributes.  With the current termcap database of
  > FreeBSD using a TERM value of "xterm" causes Emacs to fall back to 8
  > color cells, but most of the faces map into these color cells correctly.
  > The result is similar to the attached "emacs-23-xterm.png" screenshot,
  > also available at:
  > 
  >   http://people.freebsd.org/~keramida/emacs-xterm256/emacs-23-xterm.png
  > 
  > Using a TERM value of "xterm-256color", on the other hand, causes Emacs
  > to have 256 color cells, but font-locking fails to pick up the color
  > definitions of many font faces, resulting in no color at all for those
  > faces.  For example the same `M-x ielm' session does not highlight
  > strings with any color at all.  The result is similar to the attached
  > "emacs-23-xterm-256color.png" screenshot, also available at:
  > 
  >   
http://people.freebsd.org/~keramida/emacs-xterm256/emacs-23-xterm-256color.png

Emacs considers xterm to have a light background by default, and it
chooses face colors based on that.
So first step in getting this solved you want to start 
"xterm -bg white -fg black".

  > Trying `M-x customize-face RET font-lock-string-face RET' shows that
  > strings should be using "LightSalmon" as their color, but the sample
  > text near the color definition uses no color at all.  The screenshot
  > attached as "emacs-23-xterm-256color-string-face.png" shows this, and is
  > also available online at:
  > 
  >   
http://people.freebsd.org/~keramida/emacs-xterm256/emacs-23-xterm-256color-string-face.png

This looks like a problem with xterm or the termcap/terminfo settings.  Emacs
things that there are 256 colors, but when it tries to use them they
don't work correctly.

Check if xterm is compiled with 256 colors support, there's a script in
the xterm sources called 256colors2.pl, run it and see if you can get
many colors displayed.

Also try
$ tput setaf 21
it should change the foreground to blue #0000ff

$ tput setab 196
it should change the background to red #ff0000

  > The list of face-colors from `M-x list-colors-display' shows 256 colors
  > when TERM="xterm-256color" but the colors upwards of slot 16 are all
  > unnamed, as in the attached "emacs-23-xterm-256color-list.png"
  > screenshot, also available at:
  > 
  >   
http://people.freebsd.org/~keramida/emacs-xterm256/emacs-23-xterm-256color-list.png
  > 
  > I see that `color-name-rgb-alist' is populated with a list of X11 color
  > names, but these names are not used at all for face colors in xterm
  > windows that have TERM="xterm-256color".  Any ideas how I can make Emacs
  > use the already loaded colors from `color-name-rgb-alist' to populate
  > the 256 available color cells?

That's not done.
But faces can still use any color name in `color-name-rgb-alist', and
the color get mapped to one of the 256 colors available.