Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!ames!pasteur!ucbvax!hplabs!sdcrdcf!trwrb!desint!geoff
From: geoff@desint.UUCP (Geoff Kuenning)
Newsgroups: comp.windows.misc
Subject: Re: simple (dumb?) question
Message-ID: <1687@desint.UUCP>
Date: 25 Feb 88 08:43:19 GMT
References: <3132@bloom-beacon.MIT.EDU>
Reply-To: geoff@desint.UUCP (Geoff Kuenning)
Organization: Interrupt Technology Corp., Manhattan Beach, CA
Lines: 27

In article <3132@bloom-beacon.MIT.EDU> tada@athena.mit.edu (Michael Zehr)
writes:

> I've yet to see
> routines like draw_vertical_line, draw_horizontal_line,
> draw_rectangle, etc...Are the draw_line routines
> implemented so efficiently that there wouldn't be much of a speed
> savings by special-casing h. and v. lines?  Or is the current design
> philosophy to avoid special cases as much as possible?  

Current design avoids special cases at the user level, preferring them
at a lower level.  It's easy to detect horizontal and vertical lines
on the fly (because one coordinate matches) and handle them separately.
Horizontal ones are a very big win on software-driven systems, because
you can set a whole memory unit (byte or word) all at once.

> With respect to polygons and rectangles, I've done some work with
> programs that do nothing but tile areas with filled rectangles, and
> I've had to use 4-sided filled polygons.  Obviously that takes a lot
> more computation than filling a rectangle.

Not necessarily;  again this can easily be detected as a special case.
However, the X Window System (there!  I said it right! :-) has separate
calls for drawing filled and unfilled rectangles.  (But one could argue
this is a bad idea, since it increases user-level complexity for little
gain.)
-- 
	Geoff Kuenning   geoff@ITcorp.com   {uunet,trwrb}!desint!geoff