Path: utzoo!attcan!uunet!husc6!mailrus!purdue!decwrl!labrea!polya!shap
From: shap@polya.Stanford.EDU (Jonathan S. Shapiro)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Text editor help
Keywords: TextEdit, Tabs
Message-ID: <4290@polya.Stanford.EDU>
Date: 5 Oct 88 19:11:39 GMT
References: <2476@rti.UUCP> <2580001@hpausla.HP.COM> <3845@Portia.Stanford.EDU> <18288@apple.Apple.COM>
Reply-To: shap@polya.Stanford.EDU (Jonathan S. Shapiro)
Organization: Stanford University
Lines: 55

In article <18288@apple.Apple.COM> casseres@Apple.COM (David Casseres) writes:
>In article <3845@Portia.Stanford.EDU> duggie@Jessica.stanford.edu (Doug Felt) writes:
>
>>Tabs are tricky.  Who knows what tabs mean when you mix left-to-right
>>and right-to-left text (arabic)?  What standards are there for tabs
>>that are not identically spaced?  Inquiring minds want to know.

The best implementation of tabs that I have seen [note: *opinion*] is
in MicroSoft Word.  Ignoring the merits of the word processor
otherwise, MicroSoft has introduced a notion of a "typed" tabstop.
Tabstop are exactly one of:

	left justifying (the usual kind)
	right justifying
	decimal aligning (right just. if no period is in it)
	centering

These take priority over the paragraph formatting (centered, l/r/both
justfied). In a situation with multiple tabstops, the tabulation binds
(in English text) to the next tabstop to the right.

Now for word processing in general, this is fine. For Outlines and
programs, this is not so great.  Tabs (at least in the ways that I use
them) have two meanings:

	incremental indentation (e.g. C indentation style, outlines)
	positional fixation (e.g. MS Word tabs)

The problem here is that one desparately wants *both* (e.g.
emacs-style C comments in C-indented code).  Note that these two kinds
of tabs are *distinct*, and probably should be bound to different
keys.

The binding of tabs in mixed left to right (LR) and right-to-left (RL)
languages is a difficult problem.  I propose the following conventions
for RL tabs:

	When the current language is right-to-left, <tab> should
	tabulate to the next tab stop to the *left*.

	MS-word style tabs should continue to be justify as they dofor
	LR languages.

The problem for mixed text isn't particularly solvable in general -
tabs are not *user-visibly* directional. By applying the above rules
and having a way to specify the directionality of the tabs, one could
solve most problems as efectively as one does in strictly LR text.

The only other real alternative I can see is adding an attribute to
each tabstop indicating whether it applies to LR/RL/both text.  That
would seem to me (without having tried it) to be counterintuitive in
the common cases.


Jon