wxt and "persist", n-th iteration !

[<tim...@en...>]

Hi!

I'm still thinking about wxt-on-Mac, and while there is one major issue
still in the works (the last one I mailed about, i.e. the single-threaded
vs. two-threaded), I've come to think about the "persist" behaviour. Let
me remind you that the purpose of "persist" is to keep plot windows open
when gnuplot exits.

Currently, I implemented this on Unix/wxGtk by forking at exit-time. The
connection to the X server is preserved, since it's a file descriptor, and
the child process keeps running the GUI loop in the background. With wxMac
(native wxWidgets on MacOS), this doesn't work: as soon as the parent
process exits, the windows disappear.

The only solution I can think of (apart from recreating the windows one by
one in the child process, which would cause an obvious flickering) is to
fork before windows are created, i.e. *immediately* when gnuplot *starts*.
Then have the parent process do nothing but wait for the child to tell him
to exit.

The only drawback I can think of is that gnuplot has to know it has to
fork when it's launched, so the "persist" setting must be given on gnuplot
command-line. Other places where it can be set currently, in 'set wxt
persist' and in wxt configuration dialog, have to be removed.

The corresponding patch is attached. I'd like those of you who use
"persist"    (or understand what it was meant for) to comment.

As for me, I only know one user, Maxima, and the proposed patch should
satisfy it.

Best regards,

Timothée