Thanks for the very useful information, Jonathan! What I am seeing so far (for Tai Tham) is that I can get GSUB "ccmp" with "dflt" ligature substitutions to work on both FF-3.6x, FF-4x-linux, and FF-4x-osx. But GPOS "mark" with "dflt" mark-to-base don't work on any of these.
The only way I can get diacritical marks to position somewhat correctly is by using negative left bearings - which I would prefer to not do. But obviously I may have to use negative left bearings if that is the only way that actually works ... Overall all I can say is: yuck! :-( I think what I would like to do, ideally, is create a "pure" version of the font that uses only proper OpenType features. Then after that, I could add certain "corruptions" like negative left bearings. But as it currently stands, I don't even know what to use to test the "pure" version of such a font ... Any suggestions? > On Linux, we're not yet using harfbuzz-ng at all (work is in progress to move > in that direction, but it's not in current betas). So *all* text there is > going through Pango at present. >> >> Also, if I am trying to test Tai Tham Unicode fonts which utilize >> OpenType features such as mark-to-base (mark), mark-to-mark (mkmk), >> and contextual ligatures (clig) --but doing so using Latin "dflt" >> since there is no tag for Tai Tham-- is Firefox 4x really using >> Harfbuzz-ng or not? >> >> It seems possible --even likely given the kinds of results I am seeing >> so far-- that Firefox is perhaps marking the runs of text as being Tai >> Tham and so would not be using the new Harfbuzz-ng > > That's what I would expect, yes. Firefox divides the text according to > scripts (based on the Unicode character codes), and then chooses whether to > use harfbuzz-ng or platform text layout libraries for each script run. It > currently uses HB *only* for the major "simple" scripts, not for those > requiring complex shaping. > >> >> And is there any possible way to know what renderer FF is really using >> for any given run of text. I guess the answer is probably not ... > > Not really, short of reading the source to determine how it will behave. :) > > JK > > _______________________________________________ HarfBuzz mailing list HarfBuzz@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/harfbuzz