[Chicken-users] pass by value and callbacks

[pluijzer .]

Hello chickeners,

I am trying to wrap a function that accepts a function pointer with an
argument to a struct passed by value.
I don't know how to do this (and fear it is not possible) but maybe
somebody else has a solution.

A little example of what I mean:

----

#>
typedef struct { int x, y; } Point;

typedef void (*SomeCallbackFuncType)(Point point);

void someFunc(SomeCallbackFuncType callback)
{
    Point p = {1, 1};
    callback(p);
}
<#

(define-external (callbackFunction (??? point))
  void
  (print "Hello from callback!"))

((foreign-lambda void "someFunc" c-pointer) #$callbackFunction)

----

I don't actually need the the value of the object in my callback.
Maybe that helps.

Thank you in advance,
Pluijzer