[XeTeX] [luatex] Info on direction primitives/implementation

Joseph Wright joseph.wright at morningstar2.co.uk
Wed Dec 5 07:57:26 CET 2012

On 05/12/2012 00:45, Vafa Khalighi wrote:
> Yes, the limitations of TeX--XeT are:
>   * Only four primitives \beginR \endR, \beginL \endL are provided which makes
>     typesetting RTL documents very hard and complicated.
>   * The primitives above only work in horizontal mode.
>   * No way to typeset RTL tabular, the only approach is to put tabular inside an
>     RTL box which itself introduces lots of problems.
>   * \special do not work properly in RTL mode.
>   * There is no way to change the direction of boxes and even if you do by
>     trick, the order of TOC or anything that has to do with \write at shipout
>     time gets wrong.
>   * left/right skips do not get reversed in RTL, so you have to replace them
>     with each other and this is not always the case, e.g. \vbox inside \hbox
>   * \parshape is not reversed in RTL mode so you have to do some macro
>     programming and this is not always the case, e.g, \vbox inside \hbox
>   * No tool for controlling equation number; it only provides
>     \predisplaydirection which is buggy in RTL.
>   * ....

Very useful list :-) (I knew some of these, but it's nice to have them
collected up.)
Joseph Wright

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