Re: Valid UTF-8 text mangled up in GtkLabel

[Jonathan Ben Avraham <yba tkos co il>]

Hi Behdad, Gaurav,
IMHO this is *the* classic example of misapplied "bidi algorithm", that 
is, the heuristic for determining base direction based on the first 
strong directional. There is no reason ever to use this heuristic in any 
normal GUI application. In almost all Arabic, Farsi and Hebrew apps you 
know the base direction from the outset or else you want to be able to set 
is specifically. For example, email addresses are always LTR, text editing 
must always be user-selectable. It would be good to implement the same 
directional model in Gtk that Sun implemented in Java Swing TextComponent, 
though I appreciate that this would require a lot of work.
My 2c,

 - yba



On Fri, 5 Aug 2005, Behdad Esfahbod wrote:

> On Fri, 5 Aug 2005, Gaurav Jain wrote:
>
> > Hi,
> >
> > I'm trying to set the text in a GtkLabel to a UTF-8 string, which
> > contains some arabic characters first, followed by my email address in
> > angle brackets, followed by my name in round brackets.  For e.g., a
> > sample value is:
> >
> > X <gaurav somewhere com> (Gaurav Jain)
> >
> > In the above, 'X' represents a valid sequence of arabic UTF-8
> > characters.  The problem that I see is that when I run this program
> > (appended to this mail), the output shown is something like this:
> >
> > (gaurav somewhere com> (Gaurav Jain> X
> >
> > Note that the angle and round brackets are all messed up, and that
> > order of arabic and ascii words is also wrong.
>
> Apparently our milages do vary ;).
>
>
> > Does anyone know WHY this is happening?
>
> Yes, because Arabic is written from right to left, unlike Latin.
> And this behavior is part of the Unicode standard.
>
> > Just for information, I'm using GTK 2.4.14.  Also,
> > I was surprised to discover that this works fine with an older version
> > of GTK (2.0.9).
>
> Right.  Because /bidi/ was not implemented completely in that
> version.  This specific part of bidi that is causing problems for
> you is called automatic paragraph direction.
>
> > Does something special need to be done so I can get
> > it to work with GTK >= 2.4?
>
> It /is/ working.  If you like to get the behavior similar to the
> old one, you need ot insert a U+200E LEFT-TO-RIGHT MARK character
> at the beginning of the buffer.
>
>
> > Thanks,
> > Gaurav
>
> --behdad
> http://behdad.org/
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