From: John Hudson (tiro@tiro.com)
Date: Sat Nov 02 2002 - 17:44:43 EST
At 15:53 11/2/2002, Thomas Lotze wrote:
> > Ironically, the sequence c+ZWJ+t is more likely *not* to display as a
> > ligature, since the ZWJ interferes with the sequence recognised by the
> > font lookups.
>
>Does this mean that it is indeed common practice to replace every last
>occurrence of a character sequence be the corresponding ligature with
>these fonts? At least in the german language, this would be desastrous:
>there are many cases where character sequences occur but the ligature is
>not allowed, e.g. if two words are combined into one, the last letter of
>the first one does not form a ligature with the first letter of the
>second even if such a ligature exists. Don't know about other languages,
>though.
German is indeed a special case, and there are various ideas for how best
to handle German ligation. Clearly, inserting ZWJ where one wanted ligation
-- or, perhaps, ZWNJ where one didn't want it -- is an option. Using ZWNJ
is probably a better solution, if one went this route, since it would work
with existing ligature implementations in OpenType, AAT and Graphite: i.e.
it would prevent ligatures from forming. However, expecting German users to
manually enter ZWJ or ZWNJ in their documents seems highly impractical, so
an automated dictionary-driven system seems to be required. This is getting
outside my area of expertise.
For other languages, it is typical for a set of standard ligatures (usually
those involving f followed by an ascending form: fb ffb ff fh ffh fi ffi fj
ffj fk ffk fl ffl) to be on by default because these ligatures are not
merely stylistic but preserve word shape integrity by reducing white space
between the letters while avoiding distracting collisions. The well known
exception to this is found in the typography of those Turkic languages that
employ a dotless as well as a dotted i: for these languages fi and ffi
ligature formation needs to be supressed, or special ligatures need to be
provided that do not remove the dot of the i. OpenType includes a Language
System tag that allows a layout feature such as Standard Ligatures <liga>
to have different lookups for different writing systems.
Stylistic ligatures such as ct and st, are typically handled in a separate
feature, which is not on by default. Obviously in fraktur fonts the
designer might decide to include ligatures like ch and ck in the standard set.
John Hudson
Tiro Typeworks www.tiro.com
Vancouver, BC tiro@tiro.com
It is necessary that by all means and cunning,
the cursed owners of books should be persuaded
to make them available to us, either by argument
or by force. - Michael Apostolis, 1467
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