On 12-07-30 23:40, Philip TAYLOR wrote: > OK, thank you Adam. I think perhaps I was being unrealistic in > asking whether the two PDFs would be visually identical; for the > very reasons you adduce, it is clear that this can never be the > case. But differences at the syntactic level are a far greater > concern : I think one should accept that if one passes an extant > XeTeX source through LuaTeX, line and page breaks may well differ, > but if LuaTeX barfs on valid XeTeX source, that is (for me, at > least) a far greater concern (and a reason against adoption, to > be honest). I believe that the TeX world needs a "policy" on naming engine-specific commands. This is akin to the CSS browser-specific prefixes, such as "-webkit-text-security" or "-moz-font-features". XeTeX already does this: all the XeTeX-specific commands are prefixed with "XeTeX". Some of those commands are of general use (in such case, the XeTeX and LuaTeX developers should communicate to standardize a new command) while others may really not be of general use at all, as they're more-less "hacks" or ways to achieve certain effects in a way tied very much to the specific implementation of the engine.
For example, there is the XeTeX command: \XeTeXfonttype ‹font› Expands to a number corresponding to which renderer is used for a ‹font›: 0 for TEX (a legacy TFM-based font); 1 for ATSUI (usually an AAT font); 2 for ICU (an OpenType font); 3 for Graphite. which really is very much tied to how XeTeX works. *** BTW: HarfBuzz has several backends, so if it gets integrated into XeTeX, I'd advise reserving several numbers for it, e.g.: 4 for HarfBuzz native OTL 5 for HarfBuzz Uniscribe 6 for HarfBuzz Graphite *** Many other XeTeX commands such as \XeTeXfindselectorbyname also only make sense in the XeTeX environment. However, I'd say -- perhaps the LuaTeX developers could create a special "stub xetex" macro package which reimplements the XeTeX-native commands as macros that follow the same syntax as XeTeX. Many of those macros would not necessarily need to "work" i.e. do anything effectively -- but at least they would be ignored gracefully rather than failing. But I don't really know whether this is a good idea -- my knowledge of "good practices in TeX" is close to null :) As you know, I'm not really a "TeX person", i.e. I try to follow the developments but don't participate actively or use TeX. Regards, Adam -- 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
