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From: mitchell@cbmvax.commodore.com (Fred Mitchell - Product Assurance)
Newsgroups: comp.sys.amiga.programmer,comp.sys.amiga.graphics
Subject: Re: Question re. double buffering / Intuition
Keywords: Intuition, Amiga, double buffering, graphics
Message-ID: <20652@cbmvax.commodore.com>
Date: 15 Apr 91 19:39:55 GMT
References: <115475@unix.cis.pitt.edu>
Reply-To: mitchell@cbmvax.commodore.com (Fred Mitchell - Product Assurance)
Organization: The Amiga People
Lines: 33

In article <115475@unix.cis.pitt.edu> jordan@unix.cis.pitt.edu (Kenneth D Jordan) writes:
>In the course of writing various scientific applications I've often required
>double buffering for my animations.  The problem is that I've never been able
>to successfully attach gadgets to the active window nor have I been able to
>open another window or requester.  In the past I simply avoided the problem
>by restricting user interation to menu bars (which was consistent with those
>applications).  Now, however, I want and need the other features of Intuition.
>...

You might try using the 'double-screen' technique of double-buffering. You
would then have identical sets of gadgets, windows and menus on both
screens, and listen to both for input. (Easy enough, both windows on the
different screens can share the same Message Port.) You would check
the message for the approiate window, hence screen, and do a ScreenToFront()
for that particular screen, and update the imagery in the alternate
window to match the changes. Tricky, but works. It's too easy for Intuition
to get out-of-sync with the RKM double-buffering scheme, because Intuition
dosen't support it. For menu operations, you'd want to do a IDCMP_MEMUVERIFY
to give you a chance to bring the approiate screen to front before
allowing the menu to be displayed.

The only disavantage with this method is that dragging the screen down
(or pulling another screen to front) becomes a problem. If that is a
necessity, you'll have to add a gadget to turn on/off double-buffering
to allow that.

>Nick Nystrom

-Mitchell  (mitchell@cbmvax.UUCP)                       ///    ///    ///
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