[XeTeX] additional beginL endL nodes in math

[David Carlisle]

On 17 April 2015 at 13:07, Julian Bradfield <jcb+xetex at jcbradfield.org> wrote:
> On 2015-04-16, David Carlisle <d.p.carlisle at gmail.com> wrote:
>> On 16 April 2015 at 20:51, Khaled Hosny <khaledhosny at eglug.org> wrote:
>>> That was very naive and did not work when inline math is broken over
>>> multiple lines, so I reverted this and the whole TeX-XeT business. XeTeX
>>> in TeX Live 2015 should behave identical to previous versions in this
>>> area.
>> Ah OK, sorry it didn't work out. I do see the problems with \specials
>> and \writes in RTL text
>> is a real problem.
>
> It seems to me that this is a consequence of some really bad design
> decisions in TeX !
> I have wondered whether the right way to is to make a new variant of
> TeX in which there are invisible whatsits (could call them boojums,
> perhaps) which are ignored by most of TeX's list-(un)building
> activities. For example, a glue-boojum-glue sequence would be treated
> as a glue sequence, except that the boojum would remain behind when
> the glue was discarded.

possibly but in the interests of keeping divergence of tex-related
engines to a minimum
as a first approach (if different approaches were being considered)
I'd look to what luatex
is doing, where colour and directionality can be specified without
introducing new nodes
colour being an attribute of the font for example.

>
> Boojum specials would instantly solve the absurd problem of colouring
> display maths without screwing up the spacing.
>

With care it should be possible now to colour maths without affecting spacing
(although it's true that more care than one would wish is needed)




David