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From: guido@piring.cwi.nl (Guido van Rossum)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Wanted: Code for simple text interface
Message-ID: <8299@boring.cwi.nl>
Date: 31 Jul 89 21:45:48 GMT
References: <9674@phoenix.Princeton.EDU> <43528@bbn.COM> <9676@phoenix.Princeton.EDU>
Sender: news@cwi.nl
Lines: 33

Well, it seems like you want to write your own textedit-like package,
only less fancy, and with some features that textedit doesn't have (or
maybe it does, only it's hidden somewhere in the documentation).

You could begin by splitting the design in two parts (this is what
textedit also does, basically): a data structure to remember the text to
be displayed (maybe only the still editable part would be enough,
although then you couldn't reconstruct stuff that got temporarily hidden
under a desk accessory or some similar thing from outer space, not to
mention MultiFinder), and code to display it on the screen, by drawing
all characters using quickdraw operations.

Editing the buffer is easy: keep a counter of how many characters there
are, etc.

Conceptually, after each edit operation (append/erase character), you
could erase the screen and redraw everything -- if only your code were
fast enough to avoid flickering.  What you do in practice is keep some
extra data around to avoid unnecessary redrawing.  The start and ending
position of each character in the editable part of the buffer should be
sufficient, really.  Actually, you can compute this on the fly as well
-- quickdraw has some nifty calls to calculate the width of a character.
Of course, restricting yourself to a fixed-width font such as monaco
would make things a lot easier.

Etc., etc.; if you think a bit more about it you'll see it's entirely
doable, but you may decide not to implement it as it could be a lot of
work (although also a lot of fun).

--
Guido van Rossum, Centre for Mathematics and Computer Science (CWI), Amsterdam
guido@cwi.nl or mcvax!guido or guido%cwi.nl@uunet.uu.net
"You're so *digital*, girl!" -- Neneh Cherry