Re: manipulate ttf-fonts loaded with luatex

[Hans Hagen <pragma@wxs.nl>]

On 28-10-2010 7:48, Ulrike Fischer wrote:

> Hm. I do have a bit the impression as if we have here a context and
> latex philosophy clash. I'm not asking you to provide a funktion

Huh? I'm not sure what philosophy refers to, as I'm not refering to 
context but to the otf loading code; so it would be a function in the 
lua code base (it would not even be interfaced to context as it would 
invalidate most of the characters in a font).

> incorporated in the context code which does the job. _I_ want to
> write support files for the chess ttf-fonts. If I get something
> working I will perhaps add it to my package. And if something
> changes in luatex or the underlying luaotfload/context code, well
> then I will have to adjust my code.

Sure, but the first complaints would end up in khaleds, tacos or my 
mailbox unless your package is private and never ends up in tex 
distributions). The fact that it's custom in latex to overload code and 
thus create a maintaince depency does not mean that I want such a 
dependency on my code. The context philosophy is to provide hooks and 
ignore all compliants about other usage cq. don't care about usage of 
code that is not meant to be accesses directly. (Also, Khaled then 
provides the interface to the latex packages.)

> Couldn't you give some examples how to manipulate a font after it
> has been defined with \font\test (if it is possible) and then let me
> play around?

I have no clue about the lualatex interface i.e. at what point you can 
hook in code. Keep in mind that messing around with a font before or 
during loading can influence other instances of that font as some data 
is shared. Also, once the font lives at the tex end, some data is 
frozen. Because some of the font's metadata is used in otf processing 
one cannot change that data without keeping that in mind.

Anyhow, you can access some font data afterwards. In context form:

     \startluacode
         function Whatever(name)
             for k, v in pairs(fonts.ids[font.current()].descriptions) do
                 if v.name == name then
                     tex.sprint("\\char"..k.."\\relax")
                     break
                 end
             end
         end
     \stopluacode
     \font\test=file:pirat.ttf
     \def\MyChessChar#1{{\test\directlua{Whatever("#1")}}}
     \MyChessChar{c160}

This is dead slow and inefficient but as you don't want a proper 
function for it I don't care too much. Interesting is that it does not 
work out (as wis to be expected as the normal glyph access function does 
something similar).

Btw, a bit of testing at my end shows that there is something fishy with 
the font with respect to inclusion in the pdf so it can well be that the 
accessor is ok and something else is the problem.

As taco mentioned in an earlier mail, we will look into it (even it 
makes not much sense).

Hans

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