On Sat, 24 Sep 2016 12:43:03 +0200 Davide Andreoli <d...@gurumeditation.it>
said:
> 2016-09-24 7:14 GMT+02:00 Carsten Haitzler <ras...@rasterman.com>:
>
> > On Fri, 23 Sep 2016 17:24:17 -0700 Cedric BAIL <cedric.b...@free.fr> said:
> >
> > > On Fri, Sep 23, 2016 at 10:48 AM, Davide Andreoli
> > > <d...@gurumeditation.it> wrote:
> > > > 2016-09-21 4:35 GMT+02:00 Felipe Magno de Almeida <
> > > > felipe.m.alme...@gmail.com>:
> > > >> On Sun, Sep 18, 2016 at 3:35 AM, Davide Andreoli <
> > d...@gurumeditation.it>
> > > >> wrote:
> > > >> > 2016-09-18 4:30 GMT+02:00 Felipe Magno de Almeida <
> > > >> > felipe.m.alme...@gmail.com>:
> > > >> >> On Sep 17, 2016 3:53 AM, "Davide Andreoli" <d...@gurumeditation.it
> > >
> > > >> wrote:
> > > >>
> > > >> [snip]
> > > >>
> > > >> >> The problem with callbacks is not difficult to implement, but
> > difficult
> > > >> to
> > > >> >> free the void* data. It needs two function pointers and the void*
> > data
> > > >> to
> > > >> >> implement correctly and generally. Not that I'm against per se, but
> > > >> >> lifetime is the real problem.
> > > >> >
> > > >> > Indeed the lifetime of the *void data is the trickiest part, a
> > > >> free_data_cb
> > > >> > seems to me the most "correct" way to handle this, not only for
> > bindings
> > > >> > but also for C code.
> > > >> >
> > > >> > Can you explain me how promises solve this problem? where the user
> > is
> > > >> > expected to free the *data in C? in both the success/failure
> > callbacks?
> > > >>
> > > >> Promises are not generic, so their lifetime is known. The user frees
> > it in
> > > >> success/failure callback, yes.
> > > >>
> > > >
> > > > ok, thanks for the explanation. So the user have to free the *data in
> > both
> > > > success and failure callbacks... this is error prone and repetitive
> > for the
> > > > user,
> > > > I suggest instead to add a free_data cb, in this way the usage is
> > simpler
> > > > and
> > > > it also correspond better with the promise_value_set that already have
> > the
> > > > free callback.
> > >
> > > Hum, we are talking about the data pointer given when registering the
> > > callback right ? I guess it would make sense and simplify a lot of
> > > code. Should we also apply that on efl.object events too ?
> > >
> > > In that case, if NULL is given, nothing will be done on the pointer.
> > > Are we ok with this ?
> >
> > ummmm right now we provide in C a void * for cb data. what this is is
> > unknown
> > to efl and if you want a free cb we have to pass ANOTHER pointer to the
> > free
> > cb... and this also means STORING these ptrs too along with every cb. do we
> > really want to spend this extra ptr? 8 bytes on 64bit... per cb... extra.
> >
> > i see the point, but i also see the cost. :/
> >
>
> If we are really so much into optimization then promise should not be Eo
> object at all :P
difference - promises are temporary/transient and dont tend to stay around a
lot. callbacks hang out on objects by the 1000's and hang out all day like a
bad smell... :)
>
> >
> > if we do this - we do this for promises AND efl events. must be
> > symmetric/everywhere.
>
> I agree with this, we should probably provide a free_cb every time we
> accept a void *data
maybe we should use a whole struct that holds cb, data and free cb. maybe thats
a bit much? like
typedef struct _Efl_Callback Efl_Callback;
typedef void (*Efl_Data_Free_Cb) (void *data);
struct _Efl_Callback {
Efl_Event_Cb func;
const void *data;
Efl_Data_Free_Cb data_free;
};
as now we have a "bag of data" that represents something to call, what to pas
to it and how to clean up what is passed. it is a unit of data and so
expressing it as a struct might make more sense, so now we
Efl_Callback cb = {my_cb_func, my_cb_data, my_data_free};
efl_callback_add(obj, EVENT_TYPE, &cb);
--
------------- Codito, ergo sum - "I code, therefore I am" --------------
The Rasterman (Carsten Haitzler) ras...@rasterman.com
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