On 13-04-22 08:20 PM, Khaled Hosny wrote: > On Sat, Apr 20, 2013 at 10:49:26AM +0100, Jonathan Kew wrote: >> On 19/4/13 22:13, Behdad Esfahbod wrote: >> >>> - What should HB_BUFFER_FLAG_PRESERVE_DEFAULT_IGNORABLES do to variation >>> selectors? Right now they do not become visible no matter what. Is it >>> relevant whether the variation selector was actually used during glyph >>> lookup >>> or not? >> >> Yes, I think it's relevant. A variation selector that was used >> during glyph lookup has (in a sense) become "visible", manifested as >> a particular choice of glyph. I don't think it should -also- appear >> as a separate glyph, even in a "show invisibles" mode. In effect, >> the <base, VS> pair has been ligated - it's just a "ligation" that's >> handled by the cmap instead of GSUB. > > But this can be said about many other control characters, ZWJ or ZWNJ > for example, they have a visual effect. > > IMO PRESERVE_DEFAULT_IGNORABLES should simply show any default ignorable > character that is being removed from the output not as a result of > OpenType glyph substitution. One use of such feature (the only use?) is > to make visible all characters that has mysterious effects on the output > so they can be easily checked/edited, and I can see variation selectors > benefiting from this just like any other default ignorable.
Note that if the font has a lookup ligating with ZWJ / ZWNJ (or any other default-ignorable) those won't be display even with PRESERVE_DEFAULT_IGNORABLES either. We have to go out of our way to make that happen (may be very hard for GSUB). It just happens that for variation-selectors it may be easier. Though, we still have to assess what effect it would have on fonts that implement variation-selectors via GSUB instead of cmap. Does anyone know any fonts like that? behdad > Regards, > Khaled > _______________________________________________ > HarfBuzz mailing list > [email protected] > http://lists.freedesktop.org/mailman/listinfo/harfbuzz > -- behdad http://behdad.org/ _______________________________________________ HarfBuzz mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/harfbuzz
