-persist command line option and the wxWidgets terminal

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

Hi,

I am working on the bug #1527701, and I need some advice.

The bug comes from the current implementation of "persist" in the wxt=20
terminal.

This option is used by external programs, like maxima, to control=20
gnuplot. They send their commands through a pipe or a file or whatever,=20
they let gnuplot exit at the end of the commands, but as they want the=20
plot windows to stay open, they use "persist".

The X11 terminal lives in a separate process, so for this terminal the=20
"persist" option makes gnuplot main process to exit while the=20
gnuplot_x11 stays alive until the user closes all the windows.

However, the wxt terminal is not a separate process. It lives in gnuplot=20
main executable, so when gnuplot exits the plot windows can't but be=20
closed. That's why I implemented "persist" so that gnuplot won't exit=20
until all wxWidgets windows are closed. But obviously that's not what=20
maxima (and probably others, I have not tried octave) wants. I thought=20
about using fork() to duplicate the process, then close the parent=20
process so that maxima and friends will be happy, and let the child=20
process take care of the windows. Although it sounds nice, it is=20
actually dangerous as 1) fork() is not portable, 2) there are a bunch of=20
undetermined behaviours when using fork() in a multithreaded application=20
(the wxWidgets main loop lives in a separate thread, so gnuplot is=20
multithreaded in this context) or an application using X.

I'm stuck.

Do you have any idea to implement "persist" in this context ?

Best regards,

Timoth=C3=A9e

P.S. : I tend to think that "persist" was a bad idea in the first place=20
: why wouldn't maxima simply leave gnuplot alone and continue its work ?=20
But I don't want to break any established behaviour either...