[PD-dev] libpd partly working with pd instances

[Dan Wilcox]

Howdy Miller,

This looks great and is definitely something we've been excited about.

On May 11, 2014, at 6:00 AM, pd-dev-request at iem.at wrote:

> To Pd developers...
> 
> I've adapted Pd to nternally use a "pdinstance" structure to allow
> multiple schedulers (including DSP chains) to run in one address space.
> With slight modification (see below) libpd can use this to run separate
> patches asynchronously.
> 
> I tried to "instance-ize" all Pd symbols to keep them private but ran into
> seemingly insoluble problems, so am leaving all symbols global for now.
> (So patches used in pdlib, if they want to be usable in a multiple-instance
> scenaro, should protect all send/receive/table/delay/etc named objects with
> a $[0-9] somewhere.

Judging from quickly scanning the test code, the main difference on our end would be switching context between instances?

I was brainstorming a future api for multiple instances along the lines of simply adding a instance index or pointer version of each of the existing libpd api calls, such as:

    int libpd_bang(const char *destination); // current function
    int libpd_bang(t_pdinstance* instance, const char *destination); // additional instance version (probably better to use a pointer, etc)

We could then call pd_setinstance, pdinstance_new etc internally ...

    t_pdinstance* libpd_init(); // default, single use case; sets internal default instance pointer and returns it 
    int libpd_init(t_pdinstance* instance); // creates a new instance, returns 0 on success

... but in the end perhaps simply adding the new functions directly is simpler:

    t_pdinstance* libpd_init(); // returns default internal instance or null on failure

    t_pdinstance* libpd_new_instance();
    void libpd_set_instance(t_pdinstance* instance);
    

> I didn't look hard, but I thnk pdlib now will need a way to send $ arguments
> to patches via libpd_openfile() somehow.  Also, libpd_init_audio() will want to
> make number of channels per-instance, etc.  I've put some relevant comments 
> in the test program I'll include below (and sorry for the length of this
> mail!)


Ok cool. We've got something to go on, great!

--------
Dan Wilcox
@danomatika
danomatika.com
robotcowboy.com





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