Re: RFC: comint.el - comint-highlight-prompt and unreadable colors

[Dan Nicolaescu]

Miles Bader <address@hidden> writes:

  > Jari Aalto <address@hidden> writes:
  > > Have a look at these:
  > >
  > > 1) On Windows, terminal Putty, which is very popular free SSH terminal.
  > >
  > > http://cante.net/~jaalto/tmp/bug/emacs/m-x-shell-color--win32-putty.jpg
  > ...
  > > 2) On windows, displaying a rxvt terminal back to the Cygwin X11 server
  > >    from a Unix host using "-bg black -fg snow"
  > >
  > > 
http://cante.net/~jaalto/tmp/bug/emacs/m-x-shell-color--rxvt-cygwin-X11.jpg
  > 
  > In both cases it looks like Emacs doesn't realize that it's on a
  > dark-background terminal, and is using light-background mode (which
  > indeed defaults to a darkish blue for comint prompts).
  > 
  > This is a common problem, because Emacs generally _cannot_ tell the
  > background color on a terminal, so it has to guess; I don't know about
  > windows, but on X11 it defaults to assuming dark-background on terminals
  > unless the TERM environment variable is "xterm".  If TERM = "xterm",
  > Emacs assumes a light background.
  > 
  > Since rxvt sets TERM to "xterms", that's almost certainly what's
  > happening in the 2nd case.  On windows, I don't know, but it's probably
  > a similar problem.

If the term is rxvt, then it's not a good idea to set TERM to xterms.

With "xterms" no term/*.el terminal initialization file is run!

rxvt sets the variable COLORFGBG to show the default foreground and
background. Based on COLORFGBG that term/rxvt.el can determine the
default background color, and correctly decide if the background is
light or dark.

Unfortunately other terminals do not have such a feature...