[HarfBuzz] Regression with ZWJ in Indic scripts

[Behdad Esfahbod]

On 13-03-18 03:15 PM, Khaled Hosny wrote:
> The issue reported below seems to be a regression in 0.9.13, basically
> ZWJ seems to be completely ignored, with 0.9.12 I get the desired
> output.

Ok, I'm going to revert the changes to the Indic joiner handling.  While fonts
are not supposed to use presentation features to choose forms, nothing stops
them from doing so, and so fonts do that.  Which means, we can't use the
auto-joiner behavior for any of the Indic features.  Going to fix that, and
then rework the bug that actually started the work.  More comments on the bug:

  https://bugs.freedesktop.org/show_bug.cgi?id=58714

behdad

> Regards,
> Khaled
> 
> ----- Forwarded message from Ian-Mathew Hornburg <imhornburg at gmail.com> -----
> 
> From: Ian-Mathew Hornburg <imhornburg at gmail.com>
> To: xetex at tug.org
> Subject: [XeTeX] Incorrect Bengali ZWJ behavior and v2 script spec
> Reply-To: Unicode-based TeX for Mac OS X and other platforms <xetex at tug.org>
> 
> I may have identified two possible bugs in 0.9999.0: the release notes
> indicate that the version-2 OpenType Indic script tags are now supported,
> and I’ve been testing various Bengali-script fonts with the git version of
> XeTeX and a current install of TeX Live 2012 to check them for correct
> shaping behavior. I’ve posted a MWE reproducing some examples from the
> Microsoft standard here: [http://pastebin.com/mgAX8c7U].
> 
> Microsoft ships two Bengali fonts (Vrinda and Shonar Bangla; both v6.80)
> with Windows 8 that support both the older (beng) and newer (bng2) Bengali
> script specs. (Older versions of each are shipped with Windows 7 and other
> Microsoft products.) The fonts behave correctly when using the beng script
> feature, with the exception of a particular ZWJ sequence: the Microsoft
> spec [https://www.microsoft.com/typography/OpenTypeDev/bengali/intro.htm]
> says that the sequence of consonant-hasant-ZWJ-consonant should prevent a
> ligature of the two consonants, then render a half-form of the first
> consonant. XeTeX currently fails to suppress the ligature.
> 
> ----- End forwarded message -----
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-- 
behdad
http://behdad.org/