Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!apple!dlyons
From: dlyons@Apple.COM (David Lyons)
Newsgroups: comp.sys.apple
Subject: Re: 2 more IIGS programming questions
Message-ID: <32788@apple.Apple.COM>
Date: 29 Jun 89 20:51:56 GMT
References: <9760@boulder.Colorado.EDU> <32779@apple.Apple.COM>
Organization: Apple Computer Inc, Cupertino, CA
Lines: 32

In article <32779@apple.Apple.COM> dlyons@Apple.COM (David Lyons) writes:
[...]
>You can use GetPortRect to find out which part of the window you're scrolled
>to, or you can get the bounding box of the update region.  More details on
>request--gotta take off!

Let me try this once more, not under time pressure this time.

Inside your content-draw routine, BeginUpdate has already been called by the
system, so what you want to do is get the bouding box of the VisRegion (try
GetVisHandle()^^.bBox to get the smallest rectangle that encloses the part of
the window that needs to be updated.

BeginUpdate temporarily replaces the window's VisRegion with the intersection of
the VisRegion and the Update region.  The bounding box of a region is stored in
bytes 2-9 (the 3rd-10th bytes) of the block of memory the region's handle refers
to.

The part about GetPortRect is true, but checking the VisRegion is generally
better, since it often gives you a smaller area to draw (GetPortRect will give
you the part that the window is "scrolled to", but not all of that really needs
to be drawn).


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