bug#57781: missing wallpaper command

[Stefan Kangas]

Felix <felix.dick@web.de> writes:

> In my private config i prepend the wallpaper-command with "setsid",
> that way the process isn't attached to emacs and the wallpaper set by
> wbg or swaybg will stay after closing emacs.
> This is an Linux specific thing of course.

The command handling is already only relevant for Unix-like systems:
MS-Windows and Haiku use native APIs.  I'm not yet sure how to best
handle the above in wallpaper.el, but I'm looking into it.

I guess we could use "setsid", but in that case we might as well use
"nohup" as that command is mandated to be there by POSIX.  (AFAIU, on
FreeBSD you'd need to install the "util-linux" package to get setsid.)

> I'm not shure how it works for gnome and plasma, but i would think it
> makes no difference.

>From your testing, it seems like it works without it, right?