Re: Latin ligatures and Unicode

From: Asmus Freytag (
Date: Thu Dec 30 1999 - 03:11:57 EST

At 12:18 PM 12/29/99 -0800, Tex Texin wrote:

>I don't see why adding a character is preferable to adding a markup
>that operates on a point in-between characters. Seems to me if I have
>a mechanism such as a markup language, I would like all commands to go
>thru the markup and not have an alternative mechanism for markup that
>operates at a point rather than a span.

Mark pointed out (at least on the W3C side of this discussion) that spans
are tricky in that "of<ligature off>fi</ligature>ce" would need to still
allow the ff ligature, which would cross the span boundary. I find that
kind of edge case unsettling myself.

>Having two mechanisms certainly makes it more difficult to design and
>implement while insuring the two interoperate and interact reasonably.

Actually, it's not that bad. Ligatures are driven by context sensitive
mapping in the renderer. Using spans to select the base line operation
(enable/disable and simple/fancy) of the renderer would not at all need to
collide with the
<ZWL> or <ZWNL> acting to extend the context locally. In that way they are
much more like the RLM or LRM or the ZWJ and ZWNJ of bidi fame.

>Certainly, a good tool would provide easy keyboard generation of the
>markup, just as easily as adding a character would require keyboard
>generation of the character, so input is not the issue.

I've been assuming this all along. A good tool would go further and propose
most appropriate ligatures automatically, but that's not the point we need
to chase down right now.

Gary wrote:
>> I see ZWL
>> as a substitute for markup having a span of two or three characters, which
>> still makes it attractive as a new character sollution. It also seems
>> more flexible. Say that I often deal with fonts that have only ligature
>> pairs, given the choice of ff i or f fi, I always prefer ff i,
>> but my colleague prefers f fi. We both prefer ffi as a single ligature
>> if it exists in the font. What markup gives each of us the results we
>> prefer? For &=ZWL, the answer is f&fi for me, and ff&i for my colleague.
>> Note that ZWNL is not useful for this case.

actually, if you assume 'ligation enabled' across the document, then
you would place a <ZWNL> between the f and the i to get ff i.

>> I can speculate at the
>> appropriate markup language, but I'd rather hear how others have actually
>> solved this problem.

Span based methods would be very cumbersome of non-intuitive in this context.


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