[PD-dev] difference between t_canvas and t_pd

[Rich E]

Update to this: it seems that I can just use t_pd pointers to open and close
the patches, although I still need to return the t_pd *x pointer from
glob_evalfile().  I don't know which method is best for opening/closing,
with t_canvas or t_pd..

The new methods look like this:

t_pd *glob_evalfile(t_pd *ignore, t_symbol *name, t_symbol *dir)
{
    t_pd *x = 0;
    t_pd *x_loaded = 0;

/* even though binbuf_evalfile appears to take care of dspstate,
 we have to do it again here, because canvas_startdsp() assumes
 that all toplevel canvases are visible.  LATER check if this
 is still necessary -- probably not. */
    int dspstate = canvas_suspend_dsp();
    binbuf_evalfile(name, dir);
    while ((x != s__X.s_thing) && (x = s__X.s_thing))
    {
vmess(x, gensym("pop"), "i", 1);
x_loaded = x;
    }
    pd_doloadbang();
    canvas_resume_dsp(dspstate);
    return x_loaded;
}

t_pd *libpd_openfile(const char *basename, const char *dirname) {
t_pd *x = glob_evalfile(0, gensym(basename), gensym(dirname));
 pd_pushsym(x);
int dzero = canvas_getdollarzero();
pd_popsym(x);

return x;
}

void libpd_closefile(t_pd *x) {
pd_free(x);
}


I would appreciate any feedback/suggestions from you guys who know the pd
API much, much more thoroughly that myself.

Cheers,
Rich

On Sun, Feb 6, 2011 at 4:49 PM, Rich E <reakinator at gmail.com> wrote:

> I can't remember, are questions related to pd's C API appropriate for
> pd-list, or are they better asked here?  It seems that everyone who responds
> to those questions is on this list just as much, anyway.
>
> I have been mucking around with opening and closing pd patches using API
> calls instead of pd's messaging system.  The reason for this is that I would
> like to be able to manage (open/close) multiple instances of a patch, and be
> able to send each copy of the patch a unique message via its $0 argument
> (see http://www.mail-archive.com/pd-list@iem.at/msg41648.html).  So far,
> the method has been to hack glob_evalfile to look like:
>
> t_canvas *glob_evalfile(t_pd *ignore, t_symbol *name, t_symbol *dir)
> {
>     t_pd *x = 0;
> /* even though binbuf_evalfile appears to take care of dspstate,
>  we have to do it again here, because canvas_startdsp() assumes
>  that all toplevel canvases are visible.  LATER check if this
>  is still necessary -- probably not. */
>     t_canvas *x_canvas = 0;
>      int dspstate = canvas_suspend_dsp();
>     binbuf_evalfile(name, dir);
>  while ((x != s__X.s_thing) && (x = s__X.s_thing))
> {
> x_canvas = canvas_getcurrent();
>  vmess(x, gensym("pop"), "i", 1);
> }
>     pd_doloadbang();
>     canvas_resume_dsp(dspstate);
>     return x_canvas;
> }
>
> The only addition is that x_canvas is retrieved before x is 'popped' off of
> pd's global stack, and is then returned, giving me a handle to close that
> particular patch with something like:
>
> canvas_menuclose(x_canvas, 0);
>
> But I realize that in global_evalfile, t_pd and x_canvas point to the same
> address space.  This leads me to ask, what is the difference between these
> two pointers?  Is t_canvas a t_pd along with variables for its graphical
> nature?
>
> Mathieu also pointed to me (as I was using the first set of these) that
> canvas_setcurrent() and canvas_unsetcurrent() are aliases of pd_pushsym()
> and pd_popsym().  Is there a good reason to use one over the other?
>
> Last question:  Does anyone see a way that I could get the value of x in
> glob_evalfile above without changing the function?  I don't think it is a
> dangerous change (and it looks like I could just hand x.gl_pd to
> canvas_menuclose, thereby not really needing a t_canvas pointer), but I
> would of course prefer to not change the API if possible.
>
> Cheers,
> Rich
>
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