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From: greg@harvard.UUCP (Greg)
Newsgroups: net.micro.mac
Subject: Re: A QuickDraw bug.
Message-ID: <941@harvard.UUCP>
Date: Sat, 10-May-86 16:19:47 EDT
Article-I.D.: harvard.941
Posted: Sat May 10 16:19:47 1986
Date-Received: Tue, 13-May-86 03:22:16 EDT
References: <932@harvard.UUCP>
Reply-To: greg@harvard.UUCP (Greg)
Organization: Harvard
Lines: 15
Keywords: regions CopyBits
Summary: small correction.

In article <932@harvard.UUCP> greg@harvard.UUCP (Greg) writes:
>Apparently, a region is stored as a linked-list of horizontal scan lines.  When
>you move a window on the screen, the Window Manager calls CopyBits to copy the
>window contents.  Normally CopyBits runs from top to bottom, using the
>scanlines of the region in order.  However, if you are copying from a grafport,
>like the screen, to itself, then CopyBits may have to copy the image from
>bottom to top so that it won't lose information during the transfer.

Someone at General Computer who actually poked around in the ROM has pointed
out to me that a region is not stored as a linked list of horizontal scan
lines, but simply as a consecutive list of horizontal scan lines.  However,
since the scan lines have variable length, the problem persists.  The rest of
my article is correct.
-- 
gregregreg