XQueryTree is a function from xlib:
extern Status XQueryTree(
Display* /* display */,
Window /* w */,
Window* /* root_return */,
Window* /* parent_return */,
Window** /* children_return */,
unsigned int* /* nchildren_return */
);
This is how I'm pulling it into Chicken (using a 'c-function' macro I'm
using for cross-Scheme compatability):
(c-function Status XQueryTree
(Display*
Window
u32vector
u32vector
(c-pointer (c-pointer unsigned-long))
u32vector))
The tricky parameter is the 'Window**' one.
I can allocate enough storage for a pointer via:
(define children-return (allocate sizeof:c-pointer))
The trouble is, how do I portably extract the address? If I assume a
32-bit pointer size, it's easy:
(pointer-u32-ref children-return)
on a 64-bit machine, that should be:
(pointer-u64-ref children-return)
but, there is no 'pointer-u64-ref'. :-)
Once I have the address, the rest is easy; convert it to a pointer with
address->pointer, and extract individual windows with pointer-u32-ref.
For reference, Ypsilon has this procedure that I use in this sort of case:
bytevector-c-void*-ref
Larceny has:
%get-pointer