Re: Questions apon Questions

[Hans Hagen <pragma@wxs.nl>]

On 3-8-2012 13:31, Keith J. Schultz wrote:

>> Afaik at the tex end we don't need information stored in GDEF tables.
> 	O.K. I am confused! Polyglossia is being ported to LuaTeX.
> 	I have be told that certain features are required.
> 	Furthermore, as I understand the OT-Spec they are need
> 	in certain fonts and without them proper glyph selection is not
> 	possible.

I don't know Polyglossia (and don't want to look into it either). So,
what missing information are you talking of?

> 	So, what then does LuaTeX/Context to support the glyph selection
> 	process?

I'm not sure what you refer to. Any information in GDEF that is referred 
to from GSUB or GPOS is merged into those already (like anchors etc).

>>> 	2) Is GPOS still not supported in font.loader
>>
>> GSUB and GPOS are supported as dropping any of them would render the whole machinery useless.
> 	Again Confused. According to the OT-Spec. GSUB and GPOS may reference GDEF
> 	So, what is done in such a case?

The information is in the loaders gsub and gpos subtables already.

>> The luatex manual is.
> 	No Problem with that. Though, what I am looking for is also source code documention on the C-side.

partial in cweb and partial in the original fontforge code

>>> 	6) Is the font.loader mainly in Lua or C? (I have not gotten that far yet?)
>>>             (only a couple hours of work done)
>>
>> C producing a lua table
> 	I was hoping you would not have said that. No Problem just a little more work.

the few hours you mentioned is neglectable compared to dealing with the 
full scope of otf

> I will explain a little what I was up too. Over on the XeTeX list there was a discussions about Xe vs Lua.
> One point was that the seems to be a lack for script support. Another, was the lack of Polyglossia.
> Aurthur is working on porting it. It was mentioned that it might not work correctly with some indic scripts, due to the lack
> of the missing support for GDEF.
>
> My idea, getting the tables into the font loader should be the first and easiest task! That is reading the font file data along with the other stuff

keep in mind that in luatex we want to keep the tables lean and clean

> and putting into the apropriate LuaTeX-datastructures(naturally, GDEF -table would match the other OTF-LuaTeX-Table programming style).
> Then patching the others functions, if necessary, to use the GDEF during look-up!

best first figure out *what* is is missing in the gsub/gpos luatex 
tables that is present in the otf GDEF

> In other words, simplest first and bottom-up. Since LuaTeX says it is using the context code I decided to come to this list.
>
> Would you be so kind as to point me to Information how LuaTeX facilitates script handling? Or should I guess Fontforge?

it doesn't handle scripts at all .. luatex only provides access to the 
font data on the one hand and access to the typesetter at the other end 
... everything in between has to be done in lua

concerning indic ... the fonts does not have all the info so additional 
code is needed (will be in context some day soon)

Hans


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                                           Hans Hagen | PRAGMA ADE
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