some dired hints should be background jobs

[Luc Teirlinck]

Dan Jacobson wrote:

    idea, in dired with the cursor on a .pdf file, when we hit ! we get
    ! on man.pdf: [xpdf]
    [by the way, I just copy-and-pasted that line from the minibuffer
    prompt into this message and can't edit it one bit!]
    OK, but better a better default would be running xpdf in the
    background, for which the user has to type "xpdf * &" which BTW
    creates an distracting Async window. Yes, all that can be customized
    on one's own.

The `v' command (in dired) currently will run xpdf and friends in the
foreground, making it impossible to continue using emacs without
killing the xpdf job.  I agree that background would be better.
Changing the default of ! to run background jobs seems trivial, but
one would be stuck with the Async window popping up, which I agree is
distracting.  I also believe it is usually useless.  If one
inadvertently kills the useless buffer, the background job is gone
too.  I myself have M-RETURN bound (in dired) to a command that will
run xpdf and friends in the background, without any Async window
appearing.  A separate window (or frame) is created if necessary to
display output generated by the process, such as error messages and
the like, but only if necessary.  (Usually it is not.)  If people
would agree that this would be a good idea, I could send code for a
command that would either replace the `v' binding or would have a new
binding, say M-RETURN or whatever.  I could not just use my own
current code literally, since it would have to be stripped of personal
idiosyncrasies, but I do not believe that would be difficult to do.

Sincerely,

Luc.