Phil, I cannot comment on how 100% compatible LuaTeX and XeTeX are when it comes to the "core" set of TeX language and when only TeX-native fonts are used. It's possible they are 100% compatible, or that they're not -- I don't know much about this.
However: * XeTeX has several commands that were introduced in pdfTeX and are native to LuaTeX, and XeTeX reimplements them in a way that I believe is compatible. These commands include \pdfpageheight, \pdfpagewidth, \pdfsavepos and some others. * XeTeX has some commands that are native to XeTeX only such as \XeTeXpicfile, \XeTeXpdffile, \XeTeXmathaccent, \XeTeXvariation, \XeTeXOTfeaturetag, \XeTeXuseglyphmetrics, \XeTeXglyph and some others. You can use them in XeTeX but not in LuaTeX * I presume LuaTeX also has some commands or syntax aspects (esp. the injected Lua code) that will run in LuaTeX but not XeTeX * Even with the same core set of commands, if using OpenType fonts, the results between LuaTeX and XeTeX will necessarily vary. LuaTeX and XeTeX use different mechanisms when it comes to extracting glyph metrics, kerning, other positioning commands, and also different mechanisms when it comes to processing things like OpenType contextual alternates etc. -- and by using different mechanisms, it by necessity arrives at results that differ slightly. No known OpenType Layout engine out there (Microsoft Uniscribe, Monotype WorldType, Bitstream Panorama, Adobe World composer, ICU Layout, HarfBuzz, Pango, or the LuaTeX engine) is 100% compatible with any other, so the same line, or even word, may be typeset slightly differently with each of those layout engines. This will, in the end, necessarily result in different glyphs being used at times, different line-breaking being generated etc. When it comes to Unicode and OpenType, it's much more complex than the original 8-bit Western world, and cross-platform compatibility is no longer a goal that can be achieved at this time. I'd say the situation is similar to the world of web browsers: HTML, CSS and JavaScript are being actively developed, but some snapshots of the development are strictly documented by the W3C, yet other factors come into play so that a 100% pixel compatibility between Mozilla Firefox, WebKit (Chrome or Safari), Microsoft Internet Explorer and Opera is not achievable, and probably never will be. Regards, Adam On 12-07-30 23:12, Philip TAYLOR wrote: > > > Zdenek Wagner wrote: > >> If only Unicode support and access to system fonts are concerned, a >> replacement already exists, namely luatex. > > I have held back from experimenting with LuaTeX because I have > been led to believe, from this list and elsewhere, that LuaTeX > and XeTeX are not in 1:1 correspondence in terms of the syntax > and semantics of some non-Lua-related features. Are you able > to comment on this from a position of knowledge ? Or, from the > converse perspective, would you be able to assure me and others > that all extant XeTeX code will execute in LuaTeX without error > and produce a PDF that is visually indistinguishable from the > PDF that XeTeX would produce using the same source ? > > Philip Taylor > > > -------------------------------------------------- > Subscriptions, Archive, and List information, etc.: > http://tug.org/mailman/listinfo/xetex -- May success attend your efforts, -- Adam Twardoch (Remove "list." from e-mail address to contact me directly.) -------------------------------------------------- Subscriptions, Archive, and List information, etc.: http://tug.org/mailman/listinfo/xetex
