>In fact, short of having concentric circles radiating
>from the pens origin, I can't see how any pattern could work. Perhaps the
>way to go is to periodically interrupt the drawing of the line, but this
>seems rather clunky.

No, that is in fact how it's done. If you do a net-search, you can 
probably come up with a few hits on "Bresenham's line drawing algorithm". 
If you don't, it's certainly mentioned in computer science texts.

Basically, if you want to do proper dashed lines, you have to roll your 
own drawing code.

-Mars