Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!ut-sally!ut-ngp!jdm
From: jdm@ut-ngp.UUCP (Jim Meiss)
Newsgroups: comp.sys.mac
Subject: Passing EventRecords to DA's in LSC
Message-ID: <5186@ut-ngp.UUCP>
Date: Tue, 12-May-87 12:37:51 EDT
Article-I.D.: ut-ngp.5186
Posted: Tue May 12 12:37:51 1987
Date-Received: Fri, 15-May-87 01:00:07 EDT
Organization: UTexas Computation Center, Austin, Texas
Lines: 38
Keywords: csParam, LightspeedC, Desk Accessories, Casting


	According to IM I-446 when the csCode parameter is set to accEvent,
csParam contains a pointer to the eventRecord . Thus one might expect that one
could use this pointer to call DialogSelect, for example. This does not work,
however, and apparently one needs to do a complicated casting of csParam as
shown in this code fragment from AsciiDA by W. S. Blomgren, who quotes the
DA ZoomIdle by P. Dubois:
-----------------
main (p,d,n)
cntrlParam *p;
DCtlPtr d;
int n;
{
........
   switch(n) {
........ 
      case 2:         /* action in the DA */
          switch(p->csCode) {
          
               case accEvent:
                  DAevent(((EventRecord *) * (long *) &p->csParam)); 
                  
 /* casting the *address of* p->csParam as an pointer to a long, and the */
 /* long is cast as a pointer to a pointer to an eventRecord (I think?) */
 /* (from ZoomIdle 1.1 by Paul DuBois)                                   */
 /* the pointer is passed as the parameter to DAevent                    */
------------------

Can someone explain this to me? Wouldn't you think that 
	(EventRecord *) p->csParam
would be sufficient? My first try was just to pass p->csParam itself, since
its supposed to be the pointer to the eventRecord....but this definitely 
doesn't work.


						Jim Meiss
						jdm@ut-ngp.UTEXAS.EDU
						jdm@uta.MFENET.ARPA