[HarfBuzz] Ligatures and color changes

[Jonathan Kew]

On 19/2/13 23:35, Lóránt Pintér wrote:
> Using ZWNJ would be a great way of fixing it. And indeed it splits the
> ligature all right, but it also destroys the kerning. Here's a little
> test I did with HarfBuzz @ e0486fc1affd3796fb8f664e2e7fc208f1d2106c:
> (the font has an "fi" ligature, and has some kerning between "F" and ",")
>
> Splitting the ligature with the ZWNJ works:
>
> Shaped "fif\u200Ci" with features: [  ]
> Glyph: #682, x_advance: 652
> Glyph: #71, x_advance: 380
> Glyph: #3, x_advance: 0
> Glyph: #74, x_advance: 292
>
> Kerning across the ZWNJ does not:
>
> Shaped "F,F\u200C," with features: [  ]
> Glyph: #39, x_advance: 483
> Glyph: #13, x_advance: 242
> Glyph: #39, x_advance: 563
> Glyph: #3, x_advance: 0
> Glyph: #13, x_advance: 242
>
> Is it possible that doing this will be supported later in HarfBuzz?
>

Hmm - is that font using a legacy 'kern' table, or a GPOS 'kern' 
feature? For the former, I can understand that kerning would break, as 
it's a naïve glyph-pair lookup, but for the latter, I thought we should 
now ignore the ZWNJ.

JK