[HarfBuzz] Setting initial cluster value

[Kelvin Ma]

for the same reason kerning cannot happen between two different font runs,
how can arabic shaping happen across different font runs?

On Sat, Jun 25, 2016 at 1:06 PM, Kelvin Ma <kelvinsthirteen at gmail.com>
wrote:

>
> > > > Don’t you
>> > > need
>> > > > context to be ignored if the boundaries of the text you want to
>> shape
>> > > fall
>> > > > inside a cluster? Like in the string 'af[fluency s]tate' where only
>> the
>> > > > 'fluency s' is supposed to be shaped?
>> > >
>> > > Depends on why you are shaping “fluency s” alone, if it is because of,
>> > > say, font change, then you need HarfBuzz to know the context otherwise
>> > > you get broken Arabic shaping.
>> >
>> > Well font change would produce a separate run that wouldn’t know about
>> the
>> > other runs so context can only be within a same-direction, same-font
>> run.
>>
>> This is wrong, font change shouldn’t break Arabic shaping, so you have
>> to pass the context even in this case.
>>
>
> If the text consists of text strings separated by formating objects, each
> text string doesn’t know about what’s around it. Because that’s at a much
> higher level in the code and harfbuzz can only handle a single font in a
> single run at a time. To artificially jam in the neighboring runs for each
> shaping attempt would involve an inordinate amount of string concatenation
> and searching on the fly.
>
>
>>
>> > But would adding the context & using the start and finish indexes cause
>> > latin ligatures like fi to get shaped when they shouldn’t be is what I’m
>> > asking?
>>
>> No, they won’t, but why you would want to do that?
>>
>
> just asking to make sure
>
>
>>
>> Regards,
>> Khaled
>>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.freedesktop.org/archives/harfbuzz/attachments/20160625/b07135cc/attachment-0001.html>