Re: [Vala] Binding questions

["Michael B. Trausch" <mike trausch us>]

On Mon, 16 Feb 2009 00:58:16 -0200
Matías De la Puente
<mfpuente ar gmail com> wrote:

> if is a typedef of XID->CARD32->unsigned long you can also do this:
>
> [CCode (cname="CARD32")]
> public struct CARD32 : ulong {}
>
> [CCode (cname="XID")]
> public struct XID : CARD32 {}
>
> [CCode (cname="ColorMap")]
> public struct ColorMap: XID {}
>
> Try both ways and see what C code valac generates. If the parameter is
> passed by value add [SimpleType].

Ahh.  That worked beautifully, and casting is easily done.  Very cool.

One other question; if you have a C function that returns a pointer to
an array of items (say, the return type is "int *", and so in Vala
you'd say int[]), it seems to assume that the last (implicit) parameter
is the length of the array.  In other words, for the Xlib entry point
int *XListDepths(Display *d, int screen_number, int *count_return), I
have to define:

  [CCode(cname = "XListDepths")]
  public int[] get_all_depths(int screen_number);

And Vala will turn this into a call to:

  XListDepths (d, screen, &_tmp0)

... creating "&_tmp0" of type gint on its own.  What happens if there
is no such parameter (say, the list is returned and you get the count
by doing pointer arithmetic until you reach a sentinel value of some
sort), or it is in a different location (say, the first or second
parameter in the list)?

Is there somewhere in the documentation where these sorts of "edge"
cases are covered, perchance?

        --- Mike

-- 
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