the object doesn't know but the ugen graph algorithm does. if it sees that a
signal inlet is not connected it creates a new signal and adds a scalar copy
routine to the DSP chain.
the scalar value is stored in the inletunion in struct _inlet (m_obj.c) and
it's updated whenever you send a float message to the inlet.
the first inlet is somewhat special in that you can use the CLASS_MAINSIGNALIN
macro to store the scalar value directly in the class (usually named x_f).
have a look at ugen_doit in d_ugen.c:
if (!uin->i_nconnect)
{
t_float *scalar;
s3 = signal_new(dc->dc_calcsize, dc->dc_srate);
/* post("%s: unconnected signal inlet set to zero",
class_getname(u->u_obj->ob_pd)); */
if ((scalar = obj_findsignalscalar(u->u_obj, i)))
dsp_add_scalarcopy(scalar, s3->s_vec, s3->s_n);
else
dsp_add_zero(s3->s_vec, s3->s_n);
uin->i_signal = s3;
s3->s_refcount = 1;
}
> Gesendet: Dienstag, 06. März 2018 um 16:08 Uhr
> Von: Alexandros <adr...@gmail.com>
> An: Pd-List <pd-list@lists.iem.at>
> Betreff: [PD] How can a signal inlet of an object know if it's receiving a
> signal
>
> [phasor~] ([osc~], and probably other objects too) seems to be aware of
> signals being connected to its left-most inlet. Providing an argument to
> [phasor~], if there's no signal coming in its inlet, it will use its
> argument for the frequency. As soon as a signal is connected, it will
> use that signal for its frequency. As soon as this signal gets
> disconnected (even if the signal is 0), [phasor~] will go back to using
> its argument for its frequency.
>
> Reading [phasor~]'s code in d_osc.c, I can't understand how this is
> achieved. I thought of looking into canvasconnections.c from the iemguts
> library, but it's a bit too complicated for me. Still, there's this
> comment in that file:
>
> /* as Pd does not have any information about connections to inlets,
> * we have to find out ourselves
> * this is done by traversing all objects in the canvas and try
> * to find out, whether they are connected to us!
> */
>
> Does this have to do with control inlets only? How can [phasor~] know if
> it's receiving a singal in its frequency inlet?
>
>
>
> _______________________________________________
> Pd-list@lists.iem.at mailing list
> UNSUBSCRIBE and account-management ->
> https://lists.puredata.info/listinfo/pd-list
>
_______________________________________________
Pd-list@lists.iem.at mailing list
UNSUBSCRIBE and account-management ->
https://lists.puredata.info/listinfo/pd-list
