Re: fribidi & arabic shaping

["Chahine M. Hamila" <mch at chaham dot com>]

Nadim Shaikli a *crit :

> > If this is not a question of feasibility and just a desirable option, I
> > find no merit in it. I understand that asking authors to adopt FriBiDi
> > and Pango is more difficult than requesting one or the other.
>
> It is both - feasible in that you get all applications that have fribidi
> in them already supporting arabic shaping for free (which is desirable).

I thinnk I see where you're getting at, but I think there is more than that Nadim.

Let's suppose we have an application that already uses fribidi and not pango. So,
putting aside the square arabic option, we want it to shape without changing
anything?
If I understand you correctly then, in fact, that would still imply other changes
in any case.
For example, supposing a call to the ordering function doesn't order only but
shapes as well, it would mean the string would be encoded in a glyph-shapes form,
not in any standard encoding.
This would mean many things.
Assuming your output is 8-bit (i.e. a second call is made for a unicode to 8-bit
char encoding conversion is made) it would mean the conversion function would have
to be aware of what font you are using, so you would have to decide for one font
and no other (more or less, I'm simplifying here) for all fribidi applications.
Now assuming you are using a wide char unicode encoding, it would mean you are
probably going to use the upper shaped glyphs, and have suitable fonts for that.
But there's more than that. All this is ok for rendering, but would be out of
question for all other underlying operations, from saving data to making any
character-dependant string manipulation, so you would probably have to modify your
code anyway. Which then would make it easier to include Pango.
See the point? Modifying the ordering layer is simply not enough to have shaping
automatically included in the apps that already support it. The reordering acts
partly on the logical level, while the shaping acts at, and must act only at, a
very strictly visual level.
See the point?
Salaam,
Chahine