Re: Bidirectional display in GUI sessions

[Stefan Monnier]

> I have committed to the Emacs development trunk revno 99950, which
> adds implementation of bidirectional display in GUI sessions (as well
> as a few fixes for display of R2L lines on TTYs).

Thanks.

> I could only test this on MS-Windows; I have no easy access for
> development on an X-based machine.

Sad to hear.  Is there something we could do to fix this problem?

> Fortunately, with the exception of one function, all the code is in
> terminal-independent parts of Emacs display engine, so it should work
> (or break ;-) the same on any type of display.

Famout last words.

> I hope I didn't break anything in non-bidi sessions.  All the changes
> are conditioned on variables that are not set unless you set
> bidi-display-reordering non-nil.  But I was wrong about this in the
> past...

BTW, I'm now running with (setq-default bidi-display-reordering t) and
I recommend everyone do the same to help find bugs in that code.

> Last, but certainly not least: Thanks to Gerd Möllmann for his kind
> guidance and advice which was instrumental in making this happen.
> Without his help, I would never have found such a simple and elegant
> solution for implementing this feature, being quite ignorant about
> internals of the Emacs GUI display.

Would it be possible to document the design/insight of this solution
somewhere?  I.e. distill what you learned from Gerd, so it might help
other people get a deeper understanding of the workings and design of
the redisplay code.


        Stefan