[HarfBuzz] Control characters inside ligatures

[Behdad Esfahbod]

On 15-12-05 03:31 PM, Khaled Hosny wrote:
> Hi,
> 
> I just noticed that when there is a control character between character
> that form a ligature, there is a zero width space after the ligature
> with a cluster value of the first character in the ligature, for
> example:
> 
> $ hb-unicode-encode U+0066,U+200C,U+0069 | hb-shape amiri-regular.ttf
> [f_i=0+1064|space=0+0]
> 
> or 
> 
> $ hb-unicode-encode U+0066,U+00AD,U+0069 | hb-shape amiri-regular.ttf 
> [f_i=0+1064|space=0+0]
> 
> This is rather surprising as I was expecting the control character to be
> consumed inside the ligature and only the ligature glyph would remain. I
> think the current behaviour makes mapping glyphs to text indices harder
> in this case. WDYT?

I don't think it makes any difference.  It's a zero-width glyph, so it
contributes nothing to the cluster as a whole, so you still have to divide the
sum of the widths of the glyphs by the number of cursor stops and that works
the same both ways.  No?

> Regards,
> Khaled
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