Am 15.05.2013 00:51, schrieb Idris Samawi Hamid ادريس سماوي حامد:

Hi Hans,

On Tue, 14 May 2013 12:01:36 -0600, Hans Hagen wrote:

...

I'm on-and-off working on the more technical font manual and in the process also check some old code i've laying around (deciding on what to include and not). I'm also revising the tracer styles.

Which makes me wonder: are there specific additional features that one would like to see in context (mkiv only of course) with respect to font support?

This may be beyond the scope of your current plans, but worth considering: It would be nice to have a mechanism where we can override/add opentype gsub and gpos features. Early on in the history of luatex we once had a mechanism that did this using FontForge's version of Adobe Feature Files. From what I understand, the AFF syntax is finally mature and supports all lookup types:

http://www.adobe.com/devnet/opentype/afdko/topic_feature_file_syntax.html

Or maybe we have our own syntax in lua, goodies etc. Anyway, a way to control/override opentype gsub and gpos behavior would be interesting. Even if a total controller is too ambitious/unwieldy, just being able to do a few basic gsub/gpos tricks may be useful for, e.g., bugs in the font.

Anyway, something to think about.

Best wishes Idris

Hi Idris and Hans, this is a great idea. Is this not available any longer in current luatex? The fontspec (xelatex+lualatex) manual lists this as a luatex only feature (I’ve used it once some time ago). I know a lot of fonts and other problems that could be fixed this way. I’d prefer to stay with the AFF syntax which is well established. Best regards, Georg

On Wed, May 15, 2013 at 08:51:28AM -0600, Idris Samawi Hamid ادريس سماوي حامد wrote:

Hi Georg,

On Wed, 15 May 2013 00:09:22 -0600, Georg Duffner wrote:

...

I’d prefer to stay with the AFF syntax which is well established.

I wonder if the latest, virtually frozen FontForge supports the current AFF syntax or still uses an earlier version. Before AFF was complete George added the missing functionality but Adobe did not accept his additions. The former luatex support was probably based on George's modifications to the AFF syntax.

Hans and Taco know better, but I suppose a newer implementation of AFF in mkiv could be done in lua without touching the binary.

Right, the version of FontForge included in LuaTeX uses the old syntax, FontForge has dropped it for the new Adobe syntax for few years now, but it didn’t make its way into LuaTeX. Regards, Khaled

But anyway, this may very well be beyond Hans' current plans for font trickery, but it's fun to discuss possibilities.

I think there is already some (not documented way) to achieve the same effect in pure Lua code (Hans uses it to implement tlig and the likes). Regards, Khaled

On Fri, 17 May 2013 17:55:10 -0600, Hans Hagen wrote:

indeed. however the biggest challenge in patching a font runtime is where to inject the patches in the look up sequence ...

Indeed, I was thinking exactly the same thing! It needs some thought... The simplest and safest idea may be to stack user-defined gsub lookups after, and only after, the gsub lookups in the font are complete. Ditto for gpos. Best wishes Idris -- Professor Idris Samawi Hamid Department of Philosophy Colorado State University Fort Collins, CO 80523