[XeTeX] Graphite font feature changes in Gentium Plus and XeTeX

[Alan Munn]

On Jan 6, 2013, at 4:53 AM, Khaled Hosny wrote:

> On Sat, Jan 05, 2013 at 05:13:56PM -0500, Alan Munn wrote:
>> Hi everyone. 
>> 
>> The most recent version of the Gentium font
>> http://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&id=Gentium_download
>> has changed from numeric feature IDs to alpha feature IDs.  However,
>> XeTeX does not seem to be able to deal with the new alpha IDs, instead
>> converts them into huge numeric IDs instead.
>> 
>> Attached is a modified version of aat-info.tex adjusted to show use
>> the Graphite renderer. When run with the old version of Gentium Plus
>> (1.504) it correctly reports the 4 digit ID codes.  For example, the
>> low profile diacritics ID used to be 1054.
>> 
>> When run with the new version of Gentium (1.510) it reports different
>> numbers.  Now the low profile diacritic ID should be 'lopr' but XeTeX
>> thinks it's 1819242610.
> 
> The alpha numeric features id are represented internally as unsigned
> integers, is 1819242610 is (('l'<<24)|('o'<<16)|('p'<<8)|'r'), and since
> such tags were not used when XeTeX got its Graphite support, it simply
> returns the integer value.

Hi Khaled, that's what I suspected.
 
> 
> You can simply access Graphite features by their labels in this case:
> 
> \font\lowfont="Gentium Plus/GR:Low-profile diacritics=1"

 That doesn't seem to work, however:

% !TEX TS-program = XeTeX
% This document assumes version 1.510 of Gentium Plus
% This command should work, but doesn't
\font\lowalpha="Gentium Plus/GR:Low-profile diacritics=1" at 12 pt
% These commands work instead
\font\lowfont="Gentium Plus/GR:1819242610=1" at 12 pt
\font\regfont="Gentium Plus/GR:1819242610=0" at 12 pt

\lowalpha má \qquad should have low profile diacritic

\lowfont má \qquad has low profile diacritic

\regfont má \qquad has regular profile diacritic

 
\bye


Alan

-- 
Alan Munn
amunn at gmx.com