Re: window-null-event-handler semiphore

[e@flavors.com (Doug Currie, Flavors Technology, Inc.)]

At 9:36 AM 95.03.21, paul hasse wrote:
>I have installed an :after method on the window-null-event-handler.  I have
>noticed that this handler seems to be called at virtually any time.  Is this
>true?  What I need to be able to do is lock out this event handler while I do
>some processing, do the processing and then restart the event handler.  What I
>really need is a semiphore.  Any suggestions?

There are at least three options:

1) Use without-interrupts around your processing; it locks out all events

2) modify your window-null-event-handler to check a *wneh-lock* special
variable; when the variable is non-zero the method should just return.
*wneh-lock* needn't be a semaphore since it's only written by one process?
(Yes? If not, make it an up/down counter and incf/decf it inside a
without-interrupts.) Your processing should set (incf) the *wneh-lock* when
it begins, and clear (decf) the *wneh-lock* when it finishes. Use
unwind-protect.

3) during your processing, install a custom event handler that punts
null-events; again, use a let-binding to capure (possible nested) previous
handlers.

(let ((*eventhook*
       #'(lambda () (= #$nullevent (rref *current-event* :eventrecord.what)))))
  ; your processing
)

e