[Dev-luatex] Q: Can LuaTeX produce xdv?

Jonathan Fine jfine at pytex.org
Sun Jan 4 08:48:13 CET 2009

Arthur Reutenauer wrote:

>> However, your statement seems to contradict your earlier statement 
>> (snipped) that one can do
>>     Source transformed by LuaTeX to DVI and hence PDF
>> and get the same result as
>>     Source transformed directly to PDF by LuaTeX
>   I didn't write that you would get the same result.  But in most cases, it
> should still work, though.  Again, it all depends on what kind of
> information you want to put it your output file, so you should be more
> specific.

I thought I'd asked for the same result, and I also thought that you 
were answering my question.  Let me restate (better this time, I hope).

Can, in all important cases, the transformation
     Source to PDF via LuaTeX
proceed via
     Source to xdv (say via a modified LuaTeX)
and then
     xdv to PDF (say by xdvipdfm).

>> From what you've said, it seems to me that xdv contains some but not all of 
>> the features that LuaTeX would need to add to the DVI format. Are there 
>> many such features?
>   I couldn't say for sure, but if you go back to my vertical text
> sample, you can see an essential feature that DVI is lacking, as well as
> xdv: the ability to include arbitrarily modified metrics for any font.
>   In my example, I want to modify the dimensions of glyphs in a font,
> much like you would do with a virtual font.  LuaTeX allows us to emulate
> this behaviour by using the define_font callback, without going through
> an actual .vf file.  You need, roughly, to produce a Lua hash table in
> which you put new widths, heights and depths for all the glyphs in that
> font.  

An aside:  I didn't know that LuaTeX had this capability (and I'm not 
sure that using it is the right way to do vertical typesetting).

What I don't see, from what you've told me, is that xdv is not adequate 
for your example.  I'd need more information.  For example, are you 
putting what you call the emulated vf file into the output PDF?


>   In short, this demontrates that DVI and extensions lack an essential
> feature of LuaTeX, which is, not very surprisingly, Lua itself.  

But DVI lacks an essential feature of TeX, which is the TeX macro 
language.  I count this as a benefit of DVI, not a deficiency. 
Standards restrict, and by restricting enable.



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