[luatex] small script to change initial letter forms

[Pablo Rodríguez]

On 01/30/2012 08:39 AM, Paul Isambert wrote:
> Pablo Rodríguez <oinos at web.de> a écrit:
>>
>> Hi there,
>>
>> there is a typographical tradition of typesetting Greek using different
>> glyphs for initial and medial/final forms of beta, theta and phi.
>>
>> The forms are the following (initial and medial/final):
>>
>> 	βϐ ϑθ ϕφ
>>
>> OpenType allows this feature to be enabled in the font, but many fonts
>> which have both glyph forms lack the proper OpenType feature.
> 
> The easiest solution might be to apply a feature file to the font file:
> 
> http://www.adobe.com/devnet/opentype/afdko/topic_feature_file_syntax.html
> 
> (I've never done that myself so I just give the link.)

Thanks for the reply, Paul.

I'm afraid that the feature file might be easy to create, but in order
to make use of it you have to edit the font files (not allowed by
copyright law [digital fonts are protected as computer programs).

>> I guess the substitution could be performed with a small luatex script
>> that could be part of Lua(La)TeX or ConTeXt documents.
> [...]
> The script looks for beta, theta and phi in whatever form and use the
> appropriate glyph depending on what precedes (under the possibly
> simplistic assumption that an initial letter is something that is not
> preceded by a glyph node with a Greek character, i.e. with Unicode
> codepoint >= 0x0370).

I guess the assumption is right.

> You can use whatever form in whatever position, the script normalizes it
> all, so that even ``φιλοσοϕία'' will be turned to ``ϕιλοσοφία''.

Thanks for the extra feature.

> I use the brutal callback-registration form; replace it with whatever
> goes in the format you're using (is that problematic for you?).

I tried to check what a callback.register might be on section 4.1 and I
must admit... well... this is all Greek to me ;-).

My question would be how could I apply this to the whole file text
(excluding preamble and commands, only text to be typeset) and how can I
apply this to a single command such as \greektext{βὰρβαρος}?

Sorry, but I don't understand how I could do it.

Thanks for your help again,


Pablo
-- 
http://www.oudeis.tk