Perso-Arabic symbols for "year" - Persian Computing

The old Google Groups will be going away soon, but your browser is incompatible with the new version.
Message from discussion Perso-Arabic symbols for "year"
Received-SPF: pass (google.com: domain of behdad.esfah...@gmail.com designates 209.85.217.173 as permitted sender) client-ip=209.85.217.173;
From: Behdad Esfahbod <behdad.esfah...@gmail.com>
Mime-Version: 1.0 (iPhone Mail 8L1)
Date: Thu, 31 May 2012 01:00:31 -0400
Message-ID: <6856699439853869806@unknownmsgid>
Subject: Re: [p-c] Perso-Arabic symbols for "year"
To: Khaled Hosny <khaledho...@eglug.org>
Cc: Behdad Esfahbod <beh...@behdad.org>, Shervin Afshar <shervinafs...@gmail.com>, 
	Behnam Rassi <beh...@me.com>, Connie Bobroff <conn...@gmail.com>, John Hudson <j...@tiro.ca>, 
	Persian Computing <persian-computing@googlegroups.com>, 
	Harfbuzz <harfb...@lists.freedesktop.org>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable

On 2012-05-28, at 10:29 PM, Khaled Hosny <khaledho...@eglug.org> wrote:

> On Mon, May 28, 2012 at 07:50:55PM -0400, Behdad Esfahbod wrote:
>> [CC'ing Khaled and HarfBuzz list]
>>
>>>
>>>
>>>
>>
>> This block:
>>
>> feature calt {
>>  sub                                              @YearSign @Digits' loo=
kup digit2medium;
>>  sub @Digits.medium                               @YearSign @Digits' loo=
kup digit2medium;
>>  sub @Digits.medium @Digits.medium                @YearSign @Digits' loo=
kup digit2medium;
>>  sub @Digits.medium @Digits.medium @Digits.medium @YearSign @Digits' loo=
kup digit2medium;
>> } calt;
>>
>> Looks completely wrong to me in that it matches the backtrack sequence i=
n the
>> wrong order.  Ie, from what I understand, and I can be totally wrong, it
>> should have lines like this:
>>
>>  sub @YearSign @Digits.medium @Digits.medium    @Digits' lookup digit2me=
dium;
>>
>> instead of this:
>>
>>  sub @Digits.medium @Digits.medium    @YearSign @Digits' lookup digit2me=
dium;
>
> AFAIK the backtrack coverage has to be in the reverse order, if I do as
> you suggest, only first digit will be matched. This have been tested
> with FireFox=C2=B9 (hb-ng), Pango (hb-old), LibreOffice (ICU) and MS Word
> (Uniscribe), so I think it is correct=C2=B2 :)

Reporting back from the Adobe communication thread:

So, apparently Adobe meant the backtrack sequence to be in logical
order, not reversed. Combining this with Khaled's observation of the
font working can only suggest that Fontforge is producing backtrack
table in reverse. Fixing that will break all fo ts relying on that
behavior of Fontforge. Khaled is to investigate more to figure out how
to proceed.

behdad


>> I like how Scheherazade SIL implements this BTW.
>
> I wanted to do it with as fewer glyph variants as possible (was then
> obsessed with smaller file size) and Scheherazade=E2=80=99s didn=E2=80=99=
t work with
> LibreOffice last time I checked.
>
>>> Finally, can anyone make any sense of the "hacks" recommended by SIL in=
 this
>>> page in terms of what's happening with the Bidi behaviour?
>>>
>>> http://scripts.sil.org/cms/scripts/page.php?item_id=3DArabicFonts#b78d0=
9ff
>>>
>>> Do they work?
>>
>> That's what I was explaining before.  Two things:
>>
>> 1. You want to force the enclosing sign into the same bidi run as the nu=
mbers.
>> Because, as I said, before Unicode 5.1 it was classified as an Arabic Le=
tter
>> and hence RTL, whereas digits are LTR.
>
> AFAIK this is no longer an issue, it has been fixed in later Unicode
> releases and an up to date software stack should do just fine with no
> hacks.
>
> Regards,
> Khaled
>
> =C2=B9 only end of ayah not the others, but since they all share the same
>  lookup, I suspect it is a Unicode properties issue on FireFox side.
>
> =C2=B2 The last Amiri release had a thinko that didn=E2=80=99t exist in p=
revious
>  release which breaks the positioning of the digits, but the substation
>  is OK, and is already fixed on master.
Create a group - Google Groups - Google Home - Terms of Service - Privacy Policy
Account Options
