bug#32921: emacsclient obeys Xresources even when launched with -nw

[Eli Zaretskii <eliz@gnu.org>]

> From: Po Lu <luangruo@yahoo.com>
> Cc: larsi@gnus.org,  32921@debbugs.gnu.org,  jimis@gmx.net
> Date: Thu, 19 May 2022 18:19:43 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > How do you mean "never"?  We have here the code in x-win.el which does
> > that and is very old, so "never" doesn't seem to be a good description
> > of the situation.  And multi-TTY support has nothing to do with
> > multiple X displays.  AFAIU, you suggested to take the X resources
> > into consideration only for the first X display on which Emacs opens
> > its first frame.  What does this have to do with multi-TTY?
> 
> No, I suggested to take the value of Emacs.reverseVideo of each display
> (yes, they are different between different displays) into account only
> for frames created that display.

We already do that, see the information and the backtrace posted by
Lars a while ago.

The code in x-win.el does something beyond that: it caters for people
who have X resources specified on their user-private files, and want
those settings to be in effect on all displays.

(And besides, what is the chance that someone will want different
values of reverseVideo on different displays?  I think the chances for
that are nil.)

> > This is completely irrelevant.  We supported X resources in Emacs
> > forever, and I see no reason to unsupport them now.  We need to
> > discuss this under the assumption that ~/.Xresources and ~/.Xdefaults
> > will continue to have the same effect on Emacs as they did before, at
> > least optionally if not by default.  Thus, suggestions to toss that
> > support are non-starters from where I stand.
> 
> Why?

Because we will otherwise break a long-standing behavior.

> My point was that X resources in Emacs are loaded from the X
> server, and as such reverseVideo could be different from one display to
> the other.  This works fine with frame parameters that are set with
> gui_default_parameter, since that calls gui_display_get_resource with
> the dpyinfo the frame is on.  However, the existing code applies the
> value of reverseVideo of the first display to all frames, even those
> created on subsequently opened displays, which means the `reverse' frame
> parameter of those frames will not match the value of Emacs.reverseVideo
> on any display other than the first display that was created.

People who want Emacs to behave like you describe can simply remove
this setting from their ~/.Xdefaults.

> > What about the suggestion to have specially-named frame parameters in
> > default-frame-alist, which are defined from X resources and only
> > applied to GUI frames?
> 
> That would work incorrectly if Emacs was connected to two different X
> servers, each with different values of reverseVideo.

Not necessarily, because frame-parameters applied by
gui_default_parameter could override those we took from ~/.Xdefaults.