Bidi support

[Stefan Monnier <monnier@iro.umontreal.ca>]

>> I was thinking of bidi for Emacs-24
> If history is of any significance, I may not live until Emacs 24.  And
> for some strange reason, the burden of adding this feature seems to be
> on my shoulders and no one else's: no development happened in this
> direction for the last several years, even though most of the
> low-level code was sitting on a branch (courtesy of Handa-san) for the
> last 4 years.

Has this branch been kept up-to-date w.r.t the trunk?
I'd guess not.  In that case, someone should do it.

I just took a look at that branch, and it doesn't look too terrible.
It made me discover the variable direction-reversed which I didn't
even know existed (and it seems that it currently has no effect :-(

> So I'd prefer it to happen sooner rather than later, at least to the
> point where the foundations are in place and others can contribute
> the rest.

Agreed.  The more I think about it, the more I think we need to open
a new branch for "what will become emacs-24".  Kind of like what we did
with the emacs-unicode branch.  I think bidi should be one of the first
features to install on that branch.

>> but if you have code ready for it
>> and if it's not too intrusive, I'd be willing to consider it.

> It is not ``ready'' in the sense that it is not yet production
> quality.  It does not yet support all the features of the Emacs
> display engine.  But it can already display bidirectional text, for
> now only in a left-to-right paragraph and only if the text has no
> faces and overlays.  The code that reorders characters for display
> isn't activated until you flip a buffer-local variable, and then only
> in that buffer.  Is that ``not too intrusive'' enough?

I think it will stay unstable for too long, so it's not good enough for
the current trunk (which I'd like to keep for shorter-term changes).


        Stefan