> On 08 Apr 2016, at 11:34, Esteban Lorenzano <esteba...@gmail.com> wrote:
>
>
>> On 07 Apr 2016, at 14:15, Damien Pollet <damien.pollet+ph...@gmail.com
>> <mailto:damien.pollet+ph...@gmail.com>> wrote:
>>
>> I think in that case you need to pass an instance of FFIExternalValueHolder.
>
> yes.
> you can take the test FFIExternalValueHolderTests>>testCall as an example.
>
> But since it uses anonymous classes it might require a better explanation,
> there is the class comment, but basically, you do this:
>
> 1) Declare a class variable
>
> MyClass class>>initialize
> INT_PTR := FFIExternalValueHolder ofType: ‘int’.
as a larger explanation, this will create an anonymous subclass to keep “int”
values, than later you can use as a type in your function call. Some people
would call this obscure, but is a good way of solving this problem (I adopted
it from old NB).
If you want to have a named class instead an anonymous class, you can just
subclass FFIExternalValueHolder:
FFIExternalValueHolder subclass: #MyIntPtr
and then implement typeDecl class method
MyIntPtr class>>typeDecl
^ ‘int'
and this will work as the anonymous class
>
> 2) Replace "int *” in your function calls with your new type:
>
> glGetAttribute: attr into: value
> ^ self ffiCall: #( int SDL_GL_GetAttribute(SDL_GLattr attr, INT_PTR
> value) )
>
> 3) pass an instance of INT_PTR to get the value:
>
> | ptr value |
>
> ptr := INT_PTR new.
> self glGetAttribute: anAttributeIDontKnow into: ptr.
>
> value := ptr value.
>
> Esteban
>
>
>>
>> On 7 April 2016 at 17:42, Thibault Raffaillac <thibault.raffail...@inria.fr
>> <mailto:thibault.raffail...@inria.fr>> wrote:
>> Hi again,
>>
>> Does anyone know what is the state of return by reference in FFI?
>> Example:
>> glGetAttribute: attr into: value
>> <primitive: #primitiveNativeCall module: #NativeBoostPlugin error:
>> errorCode>
>> ^ self nbCall: #( int SDL_GL_GetAttribute(SDL_GLattr attr, int
>> *value) )
>>
>> On my image (50666) it does nothing on value yet (if nil, remains nil, if
>> SmallInteger 0, remains 0).
>> (SDL2 glGetAttribute: 6 into: value) should return 16.
>> I've seen NBOpenGL put "out" before value in method header, should it
>> matter? (does not make it work though)
>> Last but not least, should we attach '*' to the type or variable for FFI to
>> understand it is a pointer?
>>
>> Cheers,
>> Thibault Raffaillac
>>
>>
>
