[HarfBuzz] Decomposition and soft dotted characters

[Richard Wordingham]

On Sun, 4 Aug 2013 21:15:33 +0200
Khaled Hosny <khaledhosny at eglug.org> wrote:

> 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, 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.

On the other hand, this does ensure that U+0457 and <U+0456, U+0308>
are rendered identically.  Choosing different fonts would imply that
the interpretations were different - and even included a font-selection
hint!

In LibreOffice 4.0.2.2 on Ubuntu, sequences <U+0131, U+0308> and
<U+0456, U+0308> are barely distinguishable in Gentium - visually, there
are two blobs above, though the second (composed of two dots) is only
slightly larger at 26 points.  The striking feature in both cases is
that U+0308 is too far to the left.

Richard.