Re: Bidirectional text in tooltips

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sat, 06 Nov 2010 18:23:03 +0100
> From: Jan Djärv <jan.h.d@swipnet.se>
> CC: emacs-devel@gnu.org
> 
> Well, not sure how it is supposed to look, but here are the NS and Gtk+
> results.

Thanks.

> The first image is from NS, but Gtk+ looks the same.

This image looks good, although the string seems to be flushed to the
left; the w32 display is slightly better in this case, and so should
be the non-GTK display on X.  However, judging by the second example,
I'm guessing that this is NS-only problem, in this case as well, and
GTK did flush the text to the right, did it?

> The ! has moved to the left, maybe that is intended?

Yes, because the text is read right-to-left, so the reordering engine
shows it correctly, with the exclam at the end of the text.  (This
doesn't happen in the x-show-tip call in *scratch*, because the
trailing quote prevents that, per UBA, the Unicode Bidirectional
Algorithm.)

> For the second test, the NS does not align the same way Gtk+ does (I added
> some text to make this clear).  I guess NS is wrong here.

Yes, GTK's display is correct, NS's display is not.  Looks like NS
does not determine the paragraph direction dynamically as required by
the UBA.  Perhaps there's some NS setting outside Emacs that enables
that?

Anyway, it looks like these two toolkits produce reasonable results,
even though NS is slightly incorrect.  (I don't expect many tooltips
with mixed L2R and R2L text.)

Thanks for testing this.