Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!think!zaphod.mps.ohio-state.edu!usc!pollux.usc.edu!papa
From: papa@pollux.usc.edu (Marco Papa)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Mutual Exclude Gadgets
Keywords: Gadgets
Message-ID: <22035@usc.edu>
Date: 30 Dec 89 07:22:51 GMT
References: <947@lpami.wimsey.bc.ca> <22023@usc.edu> <555@shodha.dec.com>
Sender: news@usc.edu
Organization: Felsina Software, Los Angeles, CA
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In article <555@shodha.dec.com> ridder@elvira.enet.dec.com (Hans Ridder) writes:
>In article <22023@usc.edu> papa@pollux.usc.edu (Marco Papa) writes:
>>Most data structures (including Gadgets) have "user defined" fields at
>>the end of them.  That's where you can fool with. 

>I think your first sentence above was right on the mark though.
>I would suggest using the "User" field directly, or as a pointer to
>your extension structure.  Then future changes to the size of a
>structure would not affect you, and your *binary* would be compatible.

Absolutely. That's in fact how I recall Commodore implemented the tag 
structure Extensions to support the VGA and Viking monitors.  Make 
the user-defined field as pointer to a user-defined "struct" with
whatever fields you want, and all should be cool for future releases
(i.e. nobody should be able to fool with YOUR OWN extension).

-- Marco Papa 'Doc'
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