Path: utzoo!attcan!uunet!cs.utexas.edu!sun-barr!rutgers!cbmvax!peter
From: peter@cbmvax.commodore.com (Peter Cherna)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Accessing NewMenu UserData
Message-ID: <15157@cbmvax.commodore.com>
Date: 15 Oct 90 15:43:33 GMT
References: <9194@milton.u.washington.edu>
Reply-To: peter@cbmvax.commodore.com (Peter Cherna)
Organization: Commodore, West Chester, PA
Lines: 38

In article <9194@milton.u.washington.edu> dlarson@blake.u.washington.edu (Dale Larson) writes:
>
>I want to use the UserData field of the NewMenu struct to hold a pointer
>to a function to be called when a particular item is selected.  I am a little
>dense and/or the documentation on GTMENUITEM_GETUSERDATA() is a little scant.
>Likely a little of both.  Could someone please provide an example of what the 
>fuction call would look like?  

Let's say your function returned a BOOL and took a UWORD as its parameter:

	BOOL (*fcn)(UWORD);

	fcn = GTMENUITEM_USERDATA( ItemAddress( menu, selection ) );

	return = (*fcn)(code);

(Note that its' GTMENUITEM_USERDATA, not GTMENUITEM_GETUSERDATA.)

>(*GTMENUITEM_GETUSERDATA(ItemAddress(Menu, (long)selection)))();
>just doesn't seem to cut it with my compiler, and since cdecl doesn't
>understand the cast in the GTMENUITEM_GETUSERDATA macro, I don't either.

Your problem is that GTMENUITEM_USERDATA() returns an APTR (which
is really a void* ).  You'd have to cast that into a pointer-to-function
before you can invoke it as a function. 
>
>Thanks for any help!
>  
>--
>-Dale Larson  (dlarson@blake.u.washington.edu)


     Peter
--
     Peter Cherna, Software Engineer, Commodore-Amiga, Inc.
     {uunet|rutgers}!cbmvax!peter    peter@cbmvax.cbm.commodore.com
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