bug#22786: 25.1.50; eww arabic rendering

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: mohamed.hibti@gmail.com,  22786@debbugs.gnu.org
> Date: Tue, 01 Mar 2016 11:26:34 +1100
> 
> However, I'm not quite sure how the BDI is supposed to work.  With this
> example:
> 
> <p><bdo dir=ltr>Here's something with <bdi>العربيّ</bdi> lri.</bdo>
> 
> I would have expected that slapping FSI/PDI pairs around the Arabic text
> would isolate it from the LRO that the <bdo> introduced.  But it
> doesn't.  Should it?  Using LRI/RLI instead works, but then I would have
> to keep track of what direction the text is already in?

No, FSI..PDI is TRT in this case (unless you have <bdi dir=rtl> etc.).

There was a subtle bug in bidi.c which affected this case, now fixed
on the emacs-25 branch.  With that, you should see the expected result
in the above example.

> Anyway, this reminds me: Do we have a literal char syntax for these
> control characters?

Do we have a literal syntax for _any_ character?

Btw, these controls display as thin spaces on GUI frames, and as just
spaces on a TTY; for best results you could cover each control with an
invisible text property, which would make them entirely invisible.