Re: decomposed and precomposde glyphs

[Hans Hagen <pragma@wxs.nl>]

On 2/23/2017 4:12 PM, Ulrike Fischer wrote:
> Am Thu, 23 Feb 2017 14:08:54 +0100 schrieb Hans Hagen:
>
>>> Did you sent the second mail only for me for a reason or did you
>>> only forget to add the list? Imho this is interesting for others
>>> too.
>>
>> well, it had an attachment that you can test which is not meant for
>> context (to which i'll add a similar collapse feature, off by default of
>> course as an escape) .. if that kind of stuff makes it into the latex
>> font code is up to others
>
> I looked at the code and it actually uses an idea that I had already
> tried. The problem I couldn't solve was do decompose a glyph.
> Looking at an context example it seems that context can do it. The B
> with dot below (U+1E04) ends as BU+0323 in the pdf. But how does
> context does it? It doesn't happen with a similar latex example.
> There the U+1E04 is simply missing.
>
> And why is the dot of the first B better placed than the second?
>
>
> \starttext
> \directlua
> {
>   fonts.handlers.otf.addfeature
>   {
>     name = "compose",
>     type = "ligature",
>     data =
>         {
>           ["Ạ"]={ "A", "̣" },
>           ["Ḅ"]={ "B", "̣" },
>         },
>   }
> }
>
> \font\test={file:lmroman10-regular.otf:+compose;}
>
> \test
>
> Ḅ Ạ Ḅ %why are both B in the pdf???
>
> \stoptext

it's not a ligature but a multiple

fonts.handlers.otf.addfeature
   {
     name    = "decompose",
     type    = "multiple",
     nocheck = true, -- new trick
     data    =
         {
           ["Ḅ"] = { "Q", "̣" },
           ["Ạ"] = { "X", "̣" },
         },
   }

as with all features we check against the font so of the font has no Ḅ
nothing happens and you won't see one either (as the font has no)

i'll add the nocheck option (but of course one can expect side effects 
when a font has nothing relevant)


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                                           Hans Hagen | PRAGMA ADE
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