[lltx] [luatexbase] Change in the behaviour of \newluatexattribute ?

[Khaled Hosny]

On Fri, May 21, 2010 at 02:53:30PM +0200, Manuel Pégourié-Gonnard wrote:
> Le 21/05/2010 14:42, Khaled Hosny a écrit :
> > After spending most of the day debugging why Arabic shaping is broken in
> > the luaotfload, it turned out to be an attribute issue. The first
> > allocated attribute by \newluatexattribute is 0 and ConTeXt code don't
> > seem to like that, it specifically expects attributes used in luaotfload
> > to be < 255 and > 127.
> > 
> IMHO, it shouldn't expect that. I tend to call that broken, unless someone
> provides me with a good explanation.

There are some comments in the code, but basically Hans doesn't allocate
attributes at TeX end, and in lua he reserves ranges for special uses.
The code has a function, attributes.private, that allocates attributes
in this range, but we override it sense it doesn't check if the
attribute is already allocated, our replacement hand allocate attributes
using \newluatexattribute.

> > The problem didn't show before switch to luatexbase, so I expect there
> > was some change in how \newluatexattribute allocates new attributes.
> 
> There was a minor change, I don't remember the details right now, but indeed
> allocation didn't start at 0 previously for some reason. Since allocation should
> be a black box, I didn't expect the change to be noticeable, that's why I didn't
> announce it.

I can work around it by allocating a dummy attribute first if you don't
want to change it back, not a big deal.

> > Also, to avoid any other hidden surprises, is there a way for luaotfload
> > to assign attributes in the aforementioned range in a way that works
> > nicely with the attributes package?
> > 
> No. I can't see any nice way to to that. Well, if less than 127 attributes have
> been allocated, you could allocate dummy attributes up to 127, then start
> allocating your attributes. If more than 255 attributes have already been
> allocated, there's nothing you can do.

OK, I wanted to be on the safe side, but lets just assume there no other
problems beyond the one we just found.

Regards,
 Khaled

-- 
 Khaled Hosny
 Arabic localiser and member of Arabeyes.org team
 Free font developer