Path: utzoo!attcan!uunet!lll-winken!lll-tis!helios.ee.lbl.gov!pasteur!agate!russet!lippin
From: lippin@russet.berkeley.edu (The Apathist)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Quickdraw ovals
Message-ID: <18307@agate.BERKELEY.EDU>
Date: 14 Dec 88 21:34:54 GMT
References: <1146@tank.uchicago.edu> <18216@agate.BERKELEY.EDU> <1723@pur-phy> <22121@apple.Apple.COM>
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Reply-To: lippin@math.berkeley.edu
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In article <18216@agate.BERKELEY.EDU> I wrote:
>(While we're at the wishing well, how about fixing FrameOval so that
>it doesn't leave gaps?)

Recently parent@Apple.COM (Shean Parent) wrote:
>The way that QuickDraw draws an oval is to strike an oval inside the
>given rectangle then inset by the pen size and strike a second oval.
>The area between the two strikes is filled with the current pen
>pattern and color. If you think of it like this then it is clear why
>the ovals fall apart. The area between the two strikes closes to less
>the one pixel.

I can understand how one might mistake this for a correct algorithm at
first, but I think that it's clear now that it isn't correct.  The
ovals should be separated by the pen size, not just the bounding
rectangles.

(This leads me to wonder: does FrameRgn have the same problem?)

>It is not a bug. It was designed that way.

Regardless of how it was designed, it doesn't produce the specified
result, that is, frames of ovals.  Thus, it's a bug.

					--Tom Lippincott
					  lippin@math.berkeley.edu

	"If you call a tail a leg, how many legs does a dog have?"