Questions apon Questions

Questions apon Questions

[Keith J. Schultz]

Hi Everybody,

First off, my actual interest is in Lua(La)Tex. 

It seems that several key features of OpenType are not yet supported
by otfload. My direct interest would be GDEF and GPOS.

From my understanding of things is that such things are first developed on the
Context side the pulled in by LuaTeX.

I will be setting up a drive with a Mac OS, and the Context source distro, just to kept
things safe. I already have the LuaTeX source distro.

I have started into OT-Specifican 1.6.

I have started going top down into the lua source in the normal MacTeX 2012
distro. Just to learn how things are getting done.

So here are my Questions

	1) Is GDEF still not supported in font.loader

	2) Is GPOS still not supported in font.loader

	3)  Are there any Program Specifictions anywhere to be had
	      and where

	4)  Any Class diagrams, flow charts, UML or similar documentation
	     and where for font manager and even Context or LuaTeX

	5) Any of 3 and 4 in the source distribution?

	6) Is the font.loader mainly in Lua or C? (I have not gotten that far yet?)
           (only a couple hours of work done) 

	7)  Can I safely assume that at that there enough modularization in the code
	      sothat I can work bottom up? That is add thing needed to the font.loader{} and
	      font{}

	8) Is there any special natural language convention when discussing Context inorder to
	     differentiate between  OT-Font-Table and Lua-Tables and data structures?

I have self-taught myself LUA form the online reference(far from proficient though, but the lua 
sources for Context and LuaTeX will get me there fast or i will just fake it. Been around programming
since mid-eighties, Have learned some 20-30 programming languages( Pascal, Modula2, Cobol, PM-L, Prolog, LISP,
Perl, C, C++, Objective-C) just to mention a few. 

I think this is enough for now. Thanx in advance for any help and pointers.

regards
	Keith.

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Re: Questions apon Questions

[Hans Hagen]

On 3-8-2012 10:18, Keith J. Schultz wrote:

> I have started going top down into the lua source in the normal MacTeX 2012
> distro. Just to learn how things are getting done.
>
> So here are my Questions
>
> 	1) Is GDEF still not supported in font.loader

Afaik at the tex end we don't need information stored in GDEF tables.

> 	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.

> 	3)  Are there any Program Specifictions anywhere to be had
> 	      and where

The luatex manual describes the tables. As the code comes from fontforge 
you can use the fontforge manuals (and program) as reference.

> 	4)  Any Class diagrams, flow charts, UML or similar documentation
> 	     and where for font manager and even Context or LuaTeX

The luatex manual. I'm working on a more detailed manual for font 
handling in context (but as we sometimes go beyond what opentype 
provides it will be somewhat specialized).

> 	5) Any of 3 and 4 in the source distribution?

The luatex manual is.

> 	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

> 	7)  Can I safely assume that at that there enough modularization in the code
> 	      sothat I can work bottom up? That is add thing needed to the font.loader{} and
> 	      font{}

I guess so, that is: if you start patching the loader you need to spawn 
a separate entity of luatex (some derived work).

> 	8) Is there any special natural language convention when discussing Context inorder to
> 	     differentiate between  OT-Font-Table and Lua-Tables and data structures?

One of the things that context does is normalize and optimize the raw 
font data as provided by the loader. One can always print the tables (as 
used in context, using the table serializer).  The structure used is 
rather stable. There are also hooks to kick in extra code (for instance, 
context adds additional features.)

Hans


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                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
     tel: 038 477 53 69 | voip: 087 875 68 74 | www.pragma-ade.com
                                              | www.pragma-pod.nl
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If your question is of interest to others as well, please add an entry to the Wiki!

maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
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___________________________________________________________________________________

Re: Questions apon Questions

[Hans Hagen]

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


-----------------------------------------------------------------
                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
     tel: 038 477 53 69 | voip: 087 875 68 74 | www.pragma-ade.com
                                              | www.pragma-pod.nl
-----------------------------------------------------------------
___________________________________________________________________________________
If your question is of interest to others as well, please add an entry to the Wiki!

maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
webpage  : http://www.pragma-ade.nl / http://tex.aanhet.net
archive  : http://foundry.supelec.fr/projects/contextrev/
wiki     : http://contextgarden.net
___________________________________________________________________________________

Re: Questions apon Questions

[Khaled Hosny]

On Fri, Aug 03, 2012 at 02:05:34PM +0200, Hans Hagen wrote:
> On 3-8-2012 13:31, Keith J. Schultz wrote:
> >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

The GDEF remark over XeTeX mailing list was mine and it has nothing to do
with polyglossia at all (it is related to the OpenType 1.6
UseMarkFilteringSet flag me, you and Taco discussed while ago, that will
need syncing the fontloader with FontForge).

Regards,
 Khaled
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maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
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