On Wed, Sep 6, 2017 at 5:18 AM, Jean-Philippe André <j...@videolan.org> wrote: > 2017-09-06 16:33 GMT+09:00 Cedric Bail <ced...@ddlm.me>: > >> > -------- Original Message -------- >> > Subject: [E-devel] Proposal: automatic Event->Promise/Future >> > Local Time: September 5, 2017 6:20 AM >> > UTC Time: September 5, 2017 1:20 PM >> > From: barbi...@gmail.com >> > To: edevel <enlightenment-devel@lists.sourceforge.net> >> > >> > In many cases we use events as a single shot event, then we >> > efl_event_callback_add(), wait for the callback, then >> > efl_event_callback_del()... >> > >> > With the introduction of Promise/Future pair it would be nice to have >> > that automated, for example Efl.Io.Copier produces an event "done". >> > Most of the times when you"re using Efl.Io.Copier you only want to >> > know when it was finished or when it produced an error (event: >> > "error"). >> > >> > Then it would improve usability to do something like: >> > >> > Eina_Future *f = efl_future_event(copier, >> > EFL_IO_COPIER_EVENT_DONE, /* success event */ >> > EFL_IO_COPIER_EVENT_ERROR); /* error event */ >> > eina_future_chain(f, do_something, do_something_else, on_error); >> > >> > and all would be handled for you: add/del callbacks, resolve the >> > promise and all. >> >> Just a potential idea here, why not reverse the problem. Instead of >> implementing this future on top of this events, why not have a future and >> have this events automatically create a future when someone register a >> callback on it. This avoid completely the problem of dealing with the void* >> and seems really simple to me. >> >> > This is doable, EXCEPT events are "void *" and may go away when the >> > event callback returns. However eina_promise_resolve() will postpone >> > the future chain to another mainloop iteration -- thus needs a COPY. >> > How to copy "void *"? >> >> Filling the Eina_Value_Type from the eolian type seems quite complex to >> me. It would require to give a function to do the copy and destruction of >> the structure in eolian most likely. Also I am not sure it would work in >> all case, some object that we put in the structure are really build to only >> be alive for the duration of the callback (I am thinking about input event >> here). > > > Yeah I was also thinking the same. Input events should be duplicated with a > specific function call because they are internally reused a lot.
This is doable by EINA_VALUE_TYPE_STRUCT + Eina_Value_Struct_Desc with custom Eina_Value_Struct_Operations, see: https://git.enlightenment.org/core/efl.git/tree/src/lib/eina/eina_value.h#n2884 But you also have another option here, that is to simply use copies as usual/malloc and free, then operations are not required and will be done automatically on eina_value_setup(&my_copy_value) and eina_value_flush(&my_copy_value). when you call eina_value_type_copy(type, src, dst) it won't modify src, just read its stuff. Then this is doable: const Eina_Value_Struct src_st = { .desc = EINA_VALUE_STRUCT_DESC_EFL_INPUT, // ops (malloc/free/..) and members array .memory = input, // what your event provides }; const Eina_Value src = { .type = EINA_VALUE_TYPE_STRUCT, .value.ptr = &src_st, // struct is actually "struct description", not the final structure itself // which is at "Eina_Value_Struct->memory" }; Eina_Value dst; eina_value_copy(&src, &dst); eina_promise_resolve(p, dst); // takes owneship of "dst" ... eina_value_flush(&dst); // done by eina_future when it becomes unused If EINA_VALUE_STRUCT_DESC_EFL_INPUT does provide "ops", then it may use mempool or something like that. Otherwise it will use regular "malloc() + free()". ONLY to "dst", "src" is left untouched there (see "const" to highlight that). Each described member in EINA_VALUE_STRUCT_DESC_EFL_INPUT will be walked and the provided Eina_Value_Type->copy is used... like for string it will strdup(), for stringshare it will eina_stringshare_ref(), for Eo it will efl_ref()... for basic types it's "memcpy()". If you put a custom type there, your custom "copy" will be called. -- Gustavo Sverzut Barbieri -------------------------------------- Mobile: +55 (16) 99354-9890 ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ enlightenment-devel mailing list enlightenment-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/enlightenment-devel
