Re: Bad file pointer [was: Re: Comparing plots to Matlab]

[Søren Hauberg]

tor, 02 12 2010 kl. 23:29 +0200, skrev Shai Ayal:
> On Thu, Dec 2, 2010 at 10:37 PM, Soren Hauberg <address@hidden>
> wrote:
>         ons, 01 12 2010 kl. 23:37 -0800, skrev Michael D Godfrey:
>         > On 12/01/2010 11:05 PM, John W. Eaton wrote:
>         > > I know, but it didn't seem to be working at all without
>         them, even if
>         > > the plots were displayed to the screen.  I just tried
>         again and it
>         > > generated 22 PNG files without the pauses.  With them, I
>         got 150 PNG
>         > > files.
>         > >
>         > > jwe
>         > There is definitely a lot of randomness in this problem.
>          The only
>         > fairly reliable choice that I know of is to run locally and
>         > break up sequences into a few plots each.
>         >  Do you get the "GL2PS error: Bad file pointer"
>         > error? or something else?
>         
>         I've been trying to debug why print crashes for me (still no
>         luck).
>         During some of this debugging I started getting the "Bad file
>         pointer"
>         error, so I thought I'd look into that (hoping it would fix my
>         printing
>         issue). My *guess* (and I must stress that this is guess-work)
>         is as
>         follows:
>         
>             1. '__fltk_print__' opens some process and sends the
>         process ID (as
>                a string) to 'drawnow'.
>             2. 'drawnow' passes this string over to the gl2ps
>         renderer, which
>                converts the string to an integer and attempts to open
>         the
>                underlying stream using 'fdopen'.
>             3. The call to 'fdopen' fails!
>         
>         The real question is: why does this call fail? I believe the
>         gl2ps
>         renderer is running in a different thread, which somehow has
>         an
>         influence on the behaviour of 'fdopen'. 
> 
> 
> Since I didn't see the original problem I can't test  your patch, but
> one thing is for sure: everything runs in the same thread.

Ok! Then my hypothesis is just pure nonsense :-)
I just saw that I was able to successfully convert the string
representing the PID to a FILE pointer in 'drawnow', but not in
'fltk_backend::print_figure'. I didn't really understand why, so I
arbitrarily blamed thread issues (but I guess I was wrong).

Cheers
Soren