Path: utzoo!utgpu!water!watmath!clyde!att!alberta!ubc-cs!uw-beaver!mit-eddie!bloom-beacon!apple!claris!ames!pasteur!ucbvax!decwrl!mejac!gryphon!pnet02!collins
From: collins@pnet02.cts.com (Steven Collins)
Newsgroups: comp.sys.amiga.tech
Subject: double buffering via interrupts
Message-ID: <6015@gryphon.CTS.COM>
Date: 28 Aug 88 20:20:16 GMT
Sender: root@gryphon.CTS.COM
Organization: People-Net [pnet02], Redondo Beach, CA.
Lines: 49


Is it cool to put some blank lines up here for some reason??


I am trying to set up a double buffered screen that uses a 
vertical interrupt handler to do the flip. It works fine until
I try to depth arrange or slide the screen down, then I get a bomb
that looks like:

                         00000003.00c04fd0   or
                         00000004.00c04fd0     (always at this address...)

Here's what I try to do:

         Open a hi res custom screen
         find the view with ViewAddress()
         find the rastport for the screen
         allocate a second bitmap 
         create a rastport for the second bitmap

      then I insert a Vertical blanking interval interrupt server
      in the server chain at a priority of 1. This server
      switches the bitmaps like this:

    Scrn->ViewPort.RasInfo->BitMap=   (one of the bitmap pointers)
    MakeScreen(Scrn)
    MrgCop(view)
    LoadView(view)

This whole think works... until I try to move the screen or depth arrange.
do I need to find the view using ViewAddress within the server?
(It doesn't seem to matter...)
Is this a reasonable way to do this sort of thing? How come I always
bomb to the exact same address? Should I go back to my C64?

One last clue: if I set up the server to only do the buffer fliping
every 10 V-blanks or so, I can slide the screen down as long as I don't
go too fast, and depth arranging seems to work (at least most of the time...)

What is happening when I'm moving the screen anyway?


                  thanks in advance...       steve collins

   Don't be shy... Roast me alive...


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