Problem with gnuplot backend + popen2 + non-blocking mode

[Michael Goffioul]

Hi,

while testing some code, I noticed some problems in the
gnuplot backend when octave sends a lot of data to gnuplot
through the pipe (typically when drawing surfaces). It looks
like "unfinished" data transfer with only partial drawing.
[Note: tested under Windows/MSVC]

I noticed that the gnuplot backend no uses popen2, which
opens the communication pipes in non-blocking mode
by default. I think that at some point when the pipe buffer
gets full, some writing function calls silently fail (because
of the non-blocking mode) and the associated data gets
lost.

I did a test by manually starting gnuplot with popen2 in
blocking mode and called __go_draw_figure__ on the
stream, I didn't have the problem anymore.

Would it be a problem to use popen2 in blocking mode?

Michael.