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From: tim@ism780c.UUCP (Tim Smith)
Newsgroups: net.micro.mac
Subject: Re: bug in FillPoly?
Message-ID: <417@ism780c.UUCP>
Date: Mon, 3-Feb-86 17:02:47 EST
Article-I.D.: ism780c.417
Posted: Mon Feb  3 17:02:47 1986
Date-Received: Wed, 5-Feb-86 02:28:55 EST
References: <664@harvard.UUCP>
Reply-To: tim@ism780c.UUCP (Tim Smith)
Organization: Interactive Systems Corp., Santa Monica, CA
Lines: 52

In article <664@harvard.UUCP> matthews@harvard.UUCP (Jim Matthews) writes:
>
>       We have found what seems to be a quickdraw bug.  The code that
>triggers it is as follows (in C):
>
>       PolyHandle ph;
>
>       ph = OpenPoly();
>       MoveTo(2134,638);
>       LineTo(-5000,-4954);
>       LineTo(5000,2051);
>       LineTo(1646,882);
>       ClosePoly();
>       FillPoly(ph,white);
>
> [ describes violent system crash ]

I experimented with triangles this weekend.  The triangle with vertices
at ( 50, 50 ), ( 150*n + 50, 150*n + 50 ), ( 150*n + 50, 50 )  crashed
with an out-of-memory bomb when n was 100, but was ok at n=10.  There is
no explanation for this in the pre-final editions of IM.  However, the
final edition of IM says the following, on page I-191:

        Graphic Operations on Polygons
        ------------------------------

        Four of the operations described here - PaintPoly,
        ErasePoly, InvertPoly, and FillPoly - temporarily convert
        the polygon into a region to perform their operations.
        The amount of memory required for this temporary region
        may be far greater than the amount required by the
        polygon alone.  You can estimate the size of this region
        by scaling down the polygon with MapPoly, converting it
        into a region, checking the region's size with the Memory
        Manager function GetHandleSize, and multiplying that
        value by the factor by which you scaled down the
        polygon.

                Warning: If any horizontal or vertical line drawn
                through the polygon would intersect the polygon's
                outlie more than 50 times, the results of these
                operations are undefined

The violent crash you are getting sounds like a bug, but there may
not be enough memory to do what you want, even if you get around that
bug.  You might have to split your large polygon into several smaller
polygons and fill them one by one.

Does anyone know what property of the polygon determines the size of
the region made from it?  Is it area?
--
Tim Smith       sdcrdcf!ism780c!tim || ima!ism780!tim || ihnp4!cithep!tim