Path: utzoo!attcan!uunet!husc6!endor!stew
From: stew@endor.harvard.edu (Stew Rubenstein)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Changing a menu using a resource
Keywords: str255
Message-ID: <4602@husc6.harvard.edu>
Date: 17 May 88 13:54:26 GMT
References: <346@manta.NOSC.MIL>
Sender: news@husc6.harvard.edu
Reply-To: stew@endor.UUCP (Stew Rubenstein)
Organization: Aiken Computation Lab Harvard, Cambridge, MA
Lines: 56

In article <346@manta.NOSC.MIL> lulue@manta.NOSC.MIL (Dan Lulue ) writes:
>I want to be toggle a menu item from "Turn Herman On" to "Turn Herman
>Of", and back.
 [omitted]
>Is this correct so far?

Yup, perfect.

>Now GetResource returns a handle to the requested resource.  My question
>is how to map that handle to the strings stored in the resource?  Once I
>have a handle, what do I pass to SetItem??  Here is my GetResource call:
>
>	Handle	theHandle;
>		theHandle = GetResource ('STR ', OFFID);

A Handle is just a pointer to a pointer.  SetItem takes a StringPtr,
so if you have a menu called Albert with items Herman, George, etc.,
you typically do something like:

#define MENU_albert 1

MenuHandle albertMenu;
enum {	/* Items in the Albert menu */
	albertHerman = 1,
	albertGeorge,
	albertDashedLine1,	/* Don't forget placeholders */
	albertFred,
	...
};

and then to set the item:
	
	theHandle = GetResource ('STR ', OFFID);
	HLock (theHandle)
	SetItem (albertMenu, albertHerman, (StringPtr) *theHandle);
	HPurge (theHandle);

One other thing to worry about, depending on what development system
you're using - SetItem may expect a C string (null-terminated) and
GetResource returns a handle to a Pascal string (count byte prefixed).
LightSpeed C does it right - SetItem expects a P string so the code
above is correct.  The standard MPW interfaces do this silly
conversion, so you have to PtoCstr(*theHandle); before and
CtoPstr(*theHandle) after the SetItem.

>A more generic question is "How does one figure out how to do
something >the proper way when IM does not tell you how to do it the
proper way?

This is the kind of thing you learn by examining sample code.  Also, I
can highly recommend Knaster's books (How to Write Macintosh Programs
and Macintosh Programming Secrets, I think they're called).
Stew Rubenstein
Cambridge Scientific Computing, Inc.
UUCPnet:    seismo!harvard!rubenstein            CompuServe: 76525,421
Internet:   rubenstein@harvard.harvard.edu       MCIMail:    CSC