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From: harrow@exodus.dec.com (Jeff Harrow, NCSE LKG1-3/F16 DTN=226-7445)
Newsgroups: net.micro.mac
Subject: How to draw a Region around a random Line?
Message-ID: <4848@decwrl.DEC.COM>
Date: Mon, 18-Aug-86 11:06:11 EDT
Article-I.D.: decwrl.4848
Posted: Mon Aug 18 11:06:11 1986
Date-Received: Tue, 19-Aug-86 08:02:59 EDT
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Organization: Digital Equipment Corporation
Lines: 26

Having received  such  good  advice  from  my last question about 
rubber-band lines, I now have another:

Given that I  have a random line going from StartPt to EndPt (any 
orientation), what is a  good  way to create a rectangular Region 
around it, perhaps 2 pixels  out from the line (ie a Region which 
encloses the line but is slightly larger than the line itself, to 
make for  easier  mouse capture).  (My problem is not in actually 
creating the Region,  but  making it come out in the shape that I 
want around the line...)

My initial simplistic attempt at this (drawing a rectangle around 
it expanded by the magic "2") works fine for  vertical lines, but 
the region is less and less rectangular, and less and  less  over 
the  ends of the line (ok in the center) as the  line  approaches 
horizontal.

(Something  tells  me  that  I  wish  I'd  paid more attention to 
Trig...)

Anyway, any ideas on a generalized algorithm?

(This  doesn't   belong  here,  but  boy,  is  Lightspeed  PASCAL 
**GREAT**!)

Jeff