xlib get icon data to draw on a window

Question

For my program i need other programs icons, which i have saved in a list:

Window *windowlist(Display *display, unsigned long *length)
{
    Atom prop = XInternAtom(display, "_NET_CLIENT_LIST", False);
    Atom type;
    int form;
    unsigned long remain;
    unsigned char *list;

    if(XGetWindowProperty(display, XDefaultRootWindow(display), prop, 0, 1024, False, XA_WINDOW, &type, &form, length, &remain, &list) != Success)
    {
        return 0;
    }

    return (Window*)list;
}

I could only find solutions using Imlib2, but am searching for an easier way if possible. Basically I only want to draw these icons on a window.

Atom prop = XInternAtom(display, "_NET_WM_ICON", False);
XGetWindowProperty(display, window, prop, 0, 1 or what i need to do here?, False, XA_CARDINAl, &actual_type_return, &actual_format_return, &nitems_return, &bytes_after_return, &data);
width = (int)data; 
height = (int)data;
size = width * height;
XGetWindowProperty(display, window, prop, 2 ???, size, False, XA_CARDINAl, &actual_type_return, &actual_format_return, &nitems_return, &bytes_after_return, &data);
Pixmap = ....

I really have no clue what to do. Does someone have an example of how to get the right data or how to use it (e.g. for a pixmap)? Thank you!

Edit: Now i have a other solution (its in the source of libwnck) with XWMHints:

Pixmap icon;
int width, height;
XWMHints *hints;
hints = XGetWMHints(display, window);
if(hints)
{
  if(hints->flags & IconPixmapHint)
     icon = hints->icon_pixmap;
  if(icon != 0)
  {
     get_pixmap_geometry(icon, &width, &height) //its just XGetGeometry stuff
     XCopyArea(display, icon, drawable, gc, 0, 0, width, height 0, 0);
  }
}

Something like that.

Answer 1

Use this

gulong i=0;
    int result;
    Atom type;
    int format;
    gulong bytes_after;
    gulong *data;
    gulong nitems;


XGetWindowProperty (display,
          w,
        prop,
        0, G_MAXLONG,
        False, XA_CARDINAL , &type, &format, &nitems,
        &bytes_after, ((guchar **)&data));