[PD-dev] why some structs are defined in m_obj.c? + what are vinlets and voutlets?

[Miller Puckette]

Hi Henri -

This is a reflection of Pd's extremely data-hiding programming style - the
idea is to keep the structures hidden so that if they are changed it doesn't
break stuff.

And yes, it gets awkward in spots - especially because ugen sorting and
the like have to have accessor functions that count inlets/outlets and
so on.

The way Pd's internal code finds out about connections (in order to draw
them for instance) can be seen in the function canvas_drawlines() for
example - which uses the functions linetraverser_start() and
linetraverser_next() to find them.

cheers
Miller

On Tue, Nov 20, 2018 at 04:37:03PM +0000, Henri Augusto Bisognini wrote:
> Hi.
> 
> I'm starting to dwelve into pd's C side of things. I'm having a really hard time figuring stuff out. (i have mainly experience with more high-level languages like Java, etc)
> 
> I'm trying to experiment with some editor features and i've been wandering:
> 
> why the _inlet and _outlet structures are defined in m_obj.c instead of m_pd.h ?
> 
> This way i can't access the structure members. I'm trying to traverse an t_object's t_outlets linked list but
> 
> t_outlet *o = selected_object->te_outlet;
> o = o->o_next;
> but this throws me an "dereferencing incomplete type" error since there is no definition for t_outlet inside m_pd.
> 
>  The same goes for accessing members of t_outconnect for example, but there are two methods that allows you to traverse the connections linked list
> obj_starttraverseoutlet()       (m_imp.h)(m_obj.c)
> obj_nexttraverseoutlet()       (m_imp.h)(m_obj.c)
> But i couldn't find any method to traverse an t_object's linked list of t_outlets. The only three methods that seems to return t_outlets pointers are
> 
> t_outlet *outlet_new(t_object *owner, t_symbol *s)                                       (m_obj.c)
> t_outlet *canvas_addoutlet(t_canvas *x, t_pd *who, t_symbol *s)              (g_graph.c)
> and
> t_outlet *voutlet_getit(t_pd *x)        (g_io.c)
> which i currently do not understand but doesn't seem to be what i'm looking for.
> 
> How could i traverse from, lets say the g_editor.c file, all the t_inlets and t_outlets of an t_object?
> 
> Btw, on a second question, what exactly are vinlets and voutlets?
> 
> Cheers,
> Henri.

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