[comp.sys.mac.programmer] Bug in DiffRgn?

tom@unicads.UUCP (Tom Gerardy) (09/29/89)

I've been working on getting an update handler to be "just so" and wanted
to stop some header text from slopping over into the area above a scroll bar.
It first occured to me to modify the current clip region to exclude that area.
This didn't seem to work correctly and this is what I found using Lightsbug:

The original clip is virgin, just a rect with top, left, bottom, right of
-32767, -32767, 32767, 32767 respectively.  The region I'm trying to remove
is also rectangular: 0, 486, 81, 501.  The difference is more complicated, of
course, but the boundary rect is -32767, -32767, 81????, 32767.  This doesn't
seem correct to me!

Have I missed something essential here?  I was using 3 seperate regions each
properly created by NewRgn--all seems fine until the DiffRgn call.

For those who worry about the details: 2.5M Mac+ running Think/lightspeed
Pascal 2.02.  All start-up and control panel documents removed from the
system folder which leaves Online companion installed. System 6.0.2

	-tom

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   - Tom Gerardy             UUCP: ...!sun!sunpeaks!unicads!tom
     UNICAD, Inc.              or: ...!ncar!{sunpeaks|boulder}!unicads!tom
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parent@apple.com (Sean Parent) (09/30/89)

In article <667@unicads.UUCP> tom@unicads.UUCP (Tom Gerardy) writes:
> The original clip is virgin, just a rect with top, left, bottom, right of
> -32767, -32767, 32767, 32767 respectively.  The region I'm trying to remove
> is also rectangular: 0, 486, 81, 501.  The difference is more complicated, of
> course, but the boundary rect is -32767, -32767, 81????, 32767.  This doesn't
> seem correct to me!

There is a problem with non rectangular regions that reach 32767. You 
should start with a rectangular region that is inset a few pixels.

Sean Parent
"Quality unattainable in a reasonable amount of time."