[HarfBuzz] arabic positioning without gpos

[Behdad Esfahbod]

On 01/14/2010 05:17 PM, Evan Martin wrote:
> On Thu, Jan 14, 2010 at 12:32 PM, Khaled Hosny <khaledhosny at eglug.org> wrote:
>> On Thu, Jan 14, 2010 at 11:53:56AM -0800, Evan Martin wrote:
>>> This code obviously works for the other users of Harfbuzz, so I must
>>> be missing something in my understanding.  (Maybe the glyph advances
>>> for Arabic vowels should always be zero?
>>
>> AFAIK, yes, actually I think this is true for any glyph of combining
>> marks class.
> 
> I found this function in Pango:
> 
> /**
>  * pango_ot_buffer_set_zero_width_marks
>  * @buffer: a #PangoOTBuffer
>  * @zero_width_marks: %TRUE if characters with a mark class should
>  *  be forced to zero width.
>  *
>  * Sets whether characters with a mark class should be forced to zero width.
>  * This setting is needed for proper positioning of Arabic accents,
>  * but will produce incorrect results with standard OpenType Indic
>  * fonts.
>  *
>  * Since: 1.6
>  **/
> 
> Pango calls this from the Arabic shaper.  Perhaps such a hack belongs
> in Harfbuzz?

It will be in the new harfbuzz.  I'm not familiar enough with the old harfbuzz
shaping code to comment.

behdad