[XeTeX] additional beginL endL nodes in math

[David Carlisle]

On 14 April 2015 at 17:47, David Carlisle <d.p.carlisle at gmail.com> wrote:
> As noted in the release notes direction support now works in math
> which is a good thing but a side effect seems to be that beginL endL
> nodes are added to every math list
>


The change introduces an incompatibility between xetex and pdftex/luatex.

the following plain tex example is obviously slightly contrived but is
not untypical of the kinds
of tests formats like latex commonly do, and shows that having
incompatible directional support
between xetex and pdftex will cause maintenance problems for latex
packages that try to offer
a unified interface.


\setbox0\vbox{\raggedright \hsize35pt$a + b$\par
\global\setbox1\lastbox
\unskip\unpenalty
\global\setbox1\lastbox
}

\setbox0\hbox{\unhbox1\unskip\xdef\tst{\the\lastpenalty}}

\tst
\bye


produces 700 in pdftex or luatex and 0 in xetex.