[ikarus-users] is-type macros for ffi structs

[Eduardo Cavazos]

Hello,

Here's the procedure 'configure-request' from cons-wm:

    http://gist.github.com/246754

It's dealing with two kinds of X11 structs, XConfigureRequestEvent and
XWindowChanges. The XConfigureRequestEvent struct is declared in Scheme
(well, in the Ypsilon FFI library) as:

(c-structure XConfigureRequestEvent
              (int type)
              (unsigned-long serial)
              (Bool send_event)
              (Display* display)
              (Window parent)
              (Window window)
              (int x)
              (int y)
              (int width)
              (int height)
              (int border_width)
              (Window above)
              (int detail)
              (unsigned-long value_mask)
              )

The code for XWindowChanges is similar.

The shorthand syntax I mentioned a few days ago for standard records can
also be applied here. In this case, there'd be the macros
'is-XConfigureRequestEvent' and 'is-XWindowChanges'. Given such macros
the 'configure-request' procedure would be written as:

(define configure-request
  (let ((wc (make-XWindowChanges)))
    (lambda (ev)

      (is-XWindowChanges         wc)
      (is-XConfigureRequestEvent ev)
      
      (wc.x!            ev.x)
      (wc.y!            ev.y)
      (wc.width!        ev.width)
      (wc.height!       ev.height)
      (wc.border_width! ev.border_width)
      (wc.sibling!      ev.above)
      (wc.stack_mode!   ev.detail)
      
      (XConfigureWindow dpy ev.window ev.value_mask wc)
      
      (XSync dpy False))))

Ed