Hi everyone, Currently fontconfig does not support Unicode variation selectors. Lets fix that. Unicode defines 256 generic variation selectors, in the following ranges: U+FE00 VARIATION SELECTOR-1..U+FE0F VARIATION SELECTOR-16 U+E0100 VARIATION SELECTOR-17..U+E01EF VARIATION SELECTOR-256 OpenType encodes those in cmap subtable format 14. Fonts as such can encode pairs of characters in the cmap instead of one. The second of the pair is supposed to be a variation selector, though nothing in the table format enforces that. To support these in fontconfig, two changes are needed: - Extend FcCharSet to be able to carry variation sequences as well, - Add a FcFreeTypeCharIndex variant that takes a variation selector. (ala FT_Face_GetCharVariantIndex), Adding the latter is rather trivial. For the former, it would be easiest if we encode the variation selector and the base Unicode character in one 32-bit integer, and make sure FcCharSet handles that efficiently (this probably is currently not the case). Ideally, we'd want to encode the sequence U followed by VSx (where VSx is the VARIATION SELECTOR-x) as (U + VSx << 24). This will use the high byte of the 32bit unsigned for the variation selector number. The only problem is: there are 256, not 255, variation selectors. I submitted a proposal to Unicode to commit to not use the last one, but that was not accepted. Currently up to ~240 are used. Failing that most beautiful scheme, we can use a different shift. 21 would be the next most natural, given that Unicode numbers fit 21 bits. It just would be much harder to read a hex of a 32bit number in the FcCharSet verbose output and know what it means. So, what do people think? Lets make this happen. Thanks, -- behdad http://behdad.org/ _______________________________________________ Fontconfig mailing list Fontconfig@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/fontconfig
