[XeTeX] TeX--XeT and OpenType fonts

[Jonathan Kew]

On 01/03/2017 13:37, Joseph Wright wrote:
> My guess is for the rare 'override' case one would probably do something
> at the macro level in any case (kerning is all wrong to start with).

Kerning is all wrong if you use TFM-based typesetting and then just 
reverse the character nodes; but in principle it should be fine if you 
use OpenType and actually override the character directionality:

   \nopagenumbers
   \parindent=0pt
   \TeXXeTstate=1

   Using \fontname\font\ in TFM typesetting mode:

   LVTATVL

   \beginR LVTATVL\endR

   \bigskip

   \font\tenrmOT="[lmroman10-regular.otf]/OT" at 10pt
   \tenrmOT

   \def\rtl#1{\beginR ^^^^202e#1^^^^202c\endR}

   Using \fontname\font\ in OpenType mode:

   LVTATVL

   \rtl{LVTATVL}

   \bye


JK