bug#22154: 25.0.50; emacsclient -c "breaks" 256-color display in server

[Dan Nicolaescu]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Dan Nicolaescu <dann@gnu.org>
>> Cc: eric.hanchrow@gmail.com,  22154@debbugs.gnu.org
>> Date: Mon, 14 Dec 2015 11:39:39 -0500
>> 
>> Eli Zaretskii <eliz@gnu.org> writes:
>> 
>> >> From: Dan Nicolaescu <dann@gnu.org>
>> >> Cc: Eric Hanchrow <eric.hanchrow@gmail.com>,  22154@debbugs.gnu.org
>> >> Gcc: nnml+archive:sent-mail-2015
>> >> Date: Mon, 14 Dec 2015 01:21:26 -0500
>> >> 
>> >> Using different number of colors on different ttys should work.
>> >> I just tried it briefly, and it works fine on my Fedora machine with
>> >> 24.5.
>> >> I don't have a very recent version compiled.
>> >> 
>> >> You can try it with
>> >> $ emacs -Q -f server-start&
>> >> Then from an xterm: emacsclient -t
>> >> And then from a different one: env TERM=vt100 emacsclient -t
>> >> 
>> >> The frame in the first xterm should display some colors, the one in the
>> >> second should be b&w...
>> >
>> > This simple use case indeed (almost) works.  (To have it work better,
>> > you need the patch I posted here.)  But in general, the current
>> > implementation doesn't support this, AFAICT, for 2 reasons:
>> 
>> What exactly is the problem that your patch fixes?
>
> The fact that the default escape sequences for turning colors on or
> off are stored in global variables that get overwritten each time
> another tty is initialized.

Can you describe a behavior that is incorrect?

>
>> I don't remember all the details, but having multiple terminal frames
>> running on multiple kinds of terminals, with different color depths and
>> even background modes was heavily tested when the multi-tty work was
>> going on.  One of the usual tests was to have rxvt with both 8 and 256
>> colors and white on black and black on white (rxvt not xterm because
>> rxvt sets an environment variable with the default color and emacs can
>> decide if it's a light or dark background based on that).  It worked
>> fine.
>> Did something break meanwhile or you are dealing with some new thing
>> that was not dealt with back then? 
>
> I don't know.  It's possible that the fact that set_tty_color_mode is
> now called as part of redisplay exposed some issue.
>
> And I don't understand how could what you describe work when there's
> only one global value of tty-defined-color-alist.  Can you explain how
> that worked, given that each terminal's initialization overwrites that
> list?

Sorry, I don't remember the details, but it did work
In fact I just tried on emacs 24.5 with 3 terminals: xterm
with TERM=vt100, rxvt -fg black -bg white and rxvt -fg white -bg black.
emacsclient -t connected to the same emacs daemon
M-x list-faces-display looks correct on all 3 of the simultaneously.
Editing C code in a file displayed on the 3 terminals looks fine,
everything gets fontified with the expected colors everywhere.
Unfortunately I don't have a more recent emacs version on this machine...