On Sat, Jan 01, 2011 at 08:56:24PM +0000, Joseph Wright wrote:
> On 01/01/2011 20:43, Khaled Hosny wrote:
> >Just wondering, what benefit pdftex have over luatex (with the later
> >being an extension of the former), or is it about people who are not
> >willing/can't switch to new engine? Do we expect such people to be
> >welling/able to switch to latex3 either?
> At present there is not too much of an issue: we don't have any
> working functionality for LaTeX3 where this question really shows
> up. This may change once we have some font stuff. (As I said, I have
> some ideas in this area, which include 'shameless rip-off
> fontspec'.)
> There is quite a large body of stuff which doesn't really need
> LuaTeX: stuff in western European languages using fonts already
> available to TeX. I suspect that forcing this subset of work to drop
> pdfTeX, which is quite capable of doing the job, might be consider a
> bit 'over the top'.

Even for "western European languages" Unicode and smart fonts (both not
supported "natively" pdftex) have been the norm for decades now; 8bit
encodings and type1 fonts are obsolete and almost nobody outside tex
community is using them. There is a growing body of fonts, for example,
that can not be used with pdftex without pre-processing, if at all. The
fact that pdftex can do some jobs is just keeping with the status quo
and not moving forward, IMO. I think a new system like latex3 can be a
good opportunity to get rid of legacy craft that tex have been carrying
around over the year; no need to keep supporting it (when every one else
is moving away from it) tell the eternity.

> As I said earlier, we decided to require \pdfstrcmp after some
> applications came up where the alternatives were a bad idea
> (difference in expandability with different supported engines). So
> this might change as we develop more code. I can only comment on
> what we have now, where there is no strong case for dropping support
> for pdfTeX. (Indeed, almost all of the day-to-day testing I do uses
> pdfTeX as it remains my default engine. LuaTeX is a lot slower, I'm
> afraid, quite apart from questions about bugs introduced by the
> ongoing changes.)

I'd be interested to know more about this slowness, my own tests shows
that luatex 0.60 is just 1.3 to 1.6 as slower as pdftex, not that
significant IMO, and that is testing with "stock" format, code written
to take advantage of luatex features can be much faster than comparable
pdftex code (in context, for example, certain operations are done tens
of times faster in luatex than in pdftex).


 Khaled Hosny
 Arabic localiser and member of Arabeyes.org team
 Free font developer