[comp.sys.mac.programmer] Drawing Dashed lines

sas@tut.cis.ohio-state.edu (Scott Sutherland) (05/02/90)

In article <1581@mountn.dec.com> minow@thundr.enet.dec.com (Martin Minow) writes:
>In article <682@muleshoe.cs.utexas.edu> ted@cs.utexas.edu (Ted Woodward) 
>asks how to do dashed lines.
> [ example deleted ]
 
I also am working on a dashed line function and could use some suggestions.
My problem is a bit different though, I have two types of items that need to 
be dashed - vertical & horizontal lines (no sweat, just used an apropriate
penPat), and arcs (principly long, shallow semi-circles).  

The second of the two, the arcs, are the difficulty.  If I only had to print 
on Postscript printers, there would be no problem ( The pic comment for dashed 
lines works quite well.)  But in order to be WYSIWYG, the arcs on the screen  
(and on other printers) also need to be dashed.  

I have tried using various pen patterns, but either the fairly straight 
central portion of the arc looks good or the more curved ends looks ok (never 
great) but not both. At least it is fast.  I haven't tried using several 
different patterns for different parts of the arc.  This might work a little 
better.  

Then I tried dividing the arc up into several (actually 45) smaller arcs and 
drawing every other one.  The problems with this method are  1. it is VERY
slow on a Mac Plus or SE (which is what most of my users have), and 2.  It
takes alot of work to make the dashes all the same length (in pixels, not 
degrees of arc)  thus slowing the process down even more.

You can see my dilemma.  Does anyone know of a fairly fast method of drawing 
a dashed arc, or do I go with one of these two?  Any help will be much 
appreciated!
---
Scott Sutherland	sas@cis.ohio-state.edu
Staff Software Developer
The Ohio State University, Department of Dance