[HarfBuzz] Different results when shaping sub-sections of text

[Ebrahim Byagowi]

Hi. As somehow who reads and writes on Arabic script, I can say both are
good and acceptable and no need to worry.

On Tue, Oct 6, 2015, 10:38 PM Jamie Dale <jamiedale88+harfbuzz at gmail.com>
wrote:

> Hey all,
>
> We allow rich-text as part of our text layout system, and I've noticed
> that I sometimes get different output when shaping sub-sections of text
> (for the different rich-text styles) when compared to shaping the full text.
>
> The screenshot below is text shaped by a single call to hb_shape:
> [image: Inline images 1]
>
> The screenshot below is text where each character was shaped by a separate
> call to hb_shape (the buffer used for each shape contained the full text
> as shaping context):
> [image: Inline images 2]
>
> Clearly shaping has occurred, as the screenshot below shows each glyph
> un-shaped:
> [image: Inline images 3]
>
> I suspect that the first shape has used some ligatures, and the second
> shape was unable to do that due to being unable to combine the glyphs (I
> have previously seen this with the "fi" ligature in English).
>
> If both of these forms are considered acceptable, then I'm happy enough,
> however I'd just like to sanity check it as I'm not actually able to read
> Arabic, so I can't say whether those differences are significant or somehow
> incorrect.
>
> The font used was Amiri-Regular, and the text was "شكلي" (a sub-string
> taken from an Arabic Lorem Ipsum generator <http://ar.lipsum.com/>).
>
> Thanks,
> Jamie.
> _______________________________________________
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> HarfBuzz at lists.freedesktop.org
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>
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