[NTG-context] reencode fonts with fonts.trigger

Ulrike Fischer news3 at nililand.de
Wed Feb 23 17:46:22 CET 2011

Am Tue, 22 Feb 2011 18:05:58 +0100 schrieb Hans Hagen:

>> Khaled had another idea to manipulate (reencode) fonts: He suggested
>> to put a function in fonts.trigger. (Example below). I have some
>> questions regarding this example:

>> 1. Is there a basic flaw in the idea?
> When triggers are done, there are only empty entries in the characters 
> table so swapping them has no effect. You can add info to them but some 
> entries in them will be added when scaling takes place.

For which entries can this be a problem?

>> 5. What is the recommanded lua-code to copy/reassign/remap the
>> tables?  Does a library or some helper functions exist which would
>> make it easier to move the tables around?
> For basemode reencoding you can use the changed subtable:
> \starttext
> \directlua{
>      local function chess(tfmdata,value)
>          if value then
>              tfmdata.changed[75] = 81
>              tfmdata.changed[81] = 75
>          end
>      end
>      table.insert(fonts.triggers,"chess")
>      fonts.initializers.base.otf.chess = chess
> }
> \start
>      \font\TestA="file:SkakNew-Figurine.otf:chess=yes"  \TestA\char75 
> \char81 \par
>      \font\TestB="file:SkakNew-Figurine.otf:chess=no"   \TestB\char75 
> \char81 \par
> \stop
> \stoptext

That works fine - even with luaotfload and latex (after I understood
that "basemode" means that I must call the font with "mode=base").
But curiously the dimens of the char change a bit in latex. E.g.
\showthe\fontcharwd reports without the reencoding 8.99998pt, and
9.0pt with the reencoding. In context I get in both cases 9.0pt.

Is it possible to swap (or set) the "tounicode" value at his time so
that copy&paste gives again a "K" for the king and a "Q" for the

Ulrike Fischer 

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