Thank you, it just works!
I also had to use .by_value for parameters, of course.

I'll notify the author of ffi-swig-generator about this, its tool
doesn't produce these annotations.

Regards,

Nicolas Martyanoff

On Dec 14, 10:33 pm, Wayne Meissner <wmeiss...@gmail.com> wrote:

> You need to specify the return type as ALLEGRO_COLOR.by_value
> (same for any struct-by-value parameters).
>
> 2009/12/15 galdor <khae...@gmail.com>:
>

> > Hi,

>

> > Let's define a C function which returns a plain structure:

>

> >    typedef struct {
> >        int r, g, b, a;
> >    } ALLEGRO_COLOR;

>

> >    ALLEGRO_COLOR al_map_rgb(unsigned char r, unsigned char g,
> > unsigned char b);

>

> > Now we bind it:

>

> >    class ALLEGRO_COLOR < FFI::Struct
> >        layout :r, :float,
> >               :g, :float,
> >               :b, :float,
> >               :a, :float
> >    end

>

> >    attach_function :al_map_rgb, [:uchar, :uchar, :uchar],
> > ALLEGRO_COLOR

>

> > But the following ruby code doesn't work:

>

> >    bgcolor = al_map_rgb(20, 20, 20)
> >    fgcolor = al_map_rgb(20, 40, 80)
> >    al_clear_to_color(bgcolor)

>

> > The screen is cleared with rgb(20, 40, 80), instead of rgb(20, 20,
> > 20).
> > I don't know how stack allocation is performed, I must be doing
> > something wrong.

>

> > How should I work with stack-allocated structures ?

>

> > Regards,

>

> > Nicolas Martyanoff

>
>