Re: manipulate ttf-fonts loaded with luatex

[Hans Hagen <pragma@wxs.nl>]

On 2-11-2010 4:16, Ulrike Fischer wrote:

> and store it in a table. I need a way to reencode/reorder the font,
> so that the input "K" points to the glyph "c140". Pirat is not the
> only chessfont I have, I don't want to change the input if I change
> the font, so every chessfont should have the same internal order.

(1) you can write your own fontloader (which in the case of a symbol 
font is no big deal, i.e. just slots and dimensions and 1-to-1 mapping 
as no unicode is needed, and info about that can be found in the luatex 
manual)

(2) you can intercept the table just before it is passed to tex (for 
which you need to look into the bit of code that latex i.e. just before 
font.define is called and the table passed is the one that needs to be 
tweaked, that table conforms to the luatex spec)

> My main problem is that they are so few informations about the
> generic context font loader code. E.g. after the rereading of the
> luatex manual I came up with the following:

(3) some day I'll probably document the relevant (and public) part of 
the low level interface; till then the source is the documentation 
(probably of not much use outside context as we have a different font model)

> 1. Why is the spacing in \testb wrong if the chars have been already
> used after \test?

because the font is already loaded and frozen

> 2. Which values/tables in mytable should I reset/change too to get a
> "sane" font \testb?

whatever value you want, but before the font is passed to tex (so before 
font.define is called cq. the font define callback is finished in the 
latex code)

> 3. I can also use "mytable=fonts.ids[font.id('test')]". Is this
> better? What are the differences?

fonts.ids accessed the font info that lives at the tex end but changing 
values like widths won't have any effect on tex as they are frozen 
already (after all they end up in backend code as well)

Hans

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