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From: smc%infidel@LANL.GOV (Susan Coghlan)
Newsgroups: comp.windows.news
Subject: awaitevent in NeWS 2.0
Message-ID: <9007052137.AA12935@infidel.lanl.gov>
Date: 19 Jul 90 06:41:20 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 46

Help!
   Does anyone know why awaitevent would NOT block a process
until an event was received? for instance in the section of 
code below:
      createevent dup /Name /SPDone put expressinterest
   {
      awaitevent
      dup /Name get /SPDone eq {exit}{pop}ifelse
   } loop

this crashes on " /Name get " because there is no event
on the stack!  In fact, the event in which interest
had been expressed hadn't even occurred when it crashed.
Ok, so something weird is happening - let's check the
type of the top item on the stack after awaitevent, print
it's type, and then loop until an event is left on it. 
Here's the code:
  
   createevent dup /Name /SPDone put expressinterest
   {
      awaitevent
      % generate a message to the message window
      dup type 20 string cvs (Type: ) exch append
      (Event Received) 
      2 SendMessage
      % check type of event and exit the loop if the
      % right event 
      dup type /eventtype eq {
         dup /Name get /SPDone eq {exit}{pop}ifelse
      } if
   } loop

so what happens? Not quite what you'd expect:
before the sendevent code is executed a message is received:
   Event Received
   Type: Integer 

and then nothing - no more messages, doesn't exit the loop,
it just hangs - as if awaiting an event - even though
you send the correct event several times....

Any ideas? Other loops of this type seem to work at 
various other places in the code.........  

Susan Coghlan
smc@infidel.lanl.gov