[PD-dev] from t_symbol to t_class

[Charles Henry]

On Fri, Jan 4, 2013 at 11:36 AM, Jonathan Wilkes <jancsika at yahoo.com> wrote:

> ----- Original Message -----
> > From: IOhannes zmölnig <zmoelnig at iem.at>
> > To: pd-dev at iem.at
> > Cc:
> > Sent: Friday, January 4, 2013 4:43 AM
> > Subject: Re: [PD-dev] from t_symbol to t_class
> >
> > On 01/04/2013 07:19 AM, Miller Puckette wrote:
> >>  I think you're safe calling vmess() to pass no arguments to clip_new
> >>  (for example) - the worst that can happen is the "return value"
> > (the
> >>  global "newest" is zero.  If not it's a proper Pd object you
> > can use zgetfn()
> >>  on to test it for messages.
> >>
> >>  Main problem I see with this is that some classes like "select"
> > and "list"
> >>  are actually several classes that share a name (and which one gets
> created
> >>  depends on the arguments sent to vmess())
> >
> >
> > also, what happens if the object in question accesses some hardware
> ressource?
> > e.g. [pix_video] will try to grab an available video-source, potentially
> locking
> > a hardware device.
> > in theory this should not be aproblem, as the object will hopefully be
> freed by
> > [classinfo] asap, but in practice it might have all kinds of
> side-effects,
> > starting from short lockups of Pd to launching rockets.
>
> I'd prefer to just inspect the class without creating a new instance but I
> can't
> figure out how.
>
> Are all t_gobj linked together in one big list?
>
> -Jonathan
>

I think the t_gobj are in a list per canvas--see the canvas_dodsp method in
g_canvas.c to see how it's done.

Classes in Pd exist without having an instance of the class.  Once the
setup method is called (which for externals will require you to create an
instance), the class data structure is created and loaded with all its
methods.
However, I don't know how to get a pointer to the class, when all you know
is the symbol.

Within a class, the methods are stored in an array "c_methods".  See the
class definition in m_imp.h.  You can dump out all the symbols that have
methods by looping over the array from 0 to (c_nmethod-1) and accessing the
method's "me_name".

Chuck
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.puredata.info/pipermail/pd-dev/attachments/20130104/7c91f82e/attachment.htm>