Path: utzoo!utgpu!attcan!uunet!lll-winken!lll-tis!ames!pasteur!agate!bionet!apple!parent
From: parent@Apple.COM (Sean Parent)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Quickdraw ovals
Summary: Ovals again
Message-ID: <22253@apple.Apple.COM>
Date: 15 Dec 88 22:52:05 GMT
References: <1146@tank.uchicago.edu> <18216@agate.BERKELEY.EDU> <1723@pur-phy> <4041f351.1285f@maize.engin.umich.edu>
Organization: Apple Computer Inc., Cupertino, CA
Lines: 30

In article <4041f351.1285f@maize.engin.umich.edu>, mystone@caen.engin.umich.edu (Dean Yu) writes:
> In article <18307@agate.BERKELEY.EDU> lippin@math.berkeley.edu writes:
> >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.
> 
> >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.
> >
>    Isn't that what Shean said?  Look at what he said and what you said...

First my name is Sean. (my finger was misspelled and I didn't realize it).
If what was meant by the "ovals should be separated by the pen size" meant
that they should be seperated by the pen size at all points on the oval as if
you drug the pen around the oval then that is not what I said. If QD did this
, however, then the results would be very bad. You would get ovals whose lines
got fatter as they neared the diagnals of the bounding rectangle. This is
because QD uses a square pen.

It could be argued that QD should not use a square pen but rather one that
behaved like a line that oriented itself to be perpendiculare to the tangent
of the line or arc being drawn (I belive this is how a PostScript pen behaves)
But then you would have to change the entire QD model. This is not very likely
to happen.

Please, no discussion about why Apple should adobt Display PostScript. DPS has
pleanty of things that it can't do that QD does very nicely.

Sean