[HarfBuzz] Decomposition and soft dotted characters

[Behdad Esfahbod]

On 13-08-04 03:15 PM, Khaled Hosny wrote:
> Hi All,
> 
> This TeX.SE question[1] shows an “interesting” effect of decomposition
> and soft dotted characters; Gentium lacks ї (U+0457, CYRILLIC SMALL
> LETTER YI) so HarfBuzz decomposes it into і (U+0456) and U+0308 so we
> end up with three dots.
> 
> Not sure what to do here though, but IMO unless the font has lookups to
> remove the soft dot,

If the font has i and U+0308 but not rules to compose them, it's a font bug.
Avoiding the sequence is just working around a font bug that cannot be
detected (easily).


> such decomposition is wrong and should be avoided
> as it would just fool applications depending on HarfBuzz output to
> determine if font fallback is needed or not since, IMO, using a fallback
> font is better here.

But then if the user has the i,U+0308 sequence they would hit the bug still
and there's no way to avoid that.

I don't think there's anything to be done here.

At any rate, something to reconsider if / when we add itemization support.
Right now we don't tell apps whether the font supports the sequence or not.
The app chooses the font and we just do our best at shaping with it.

-- 
behdad
http://behdad.org/