l3backend: adding new DVI specials?

[Joseph Wright]

On 19/02/2020 01:13, Norbert Preining wrote:
> Hi Joseph,
> 
> coming back to this ...
> 
>>      \special{header=l3backend-dvips.pro}
> 
> Ok, so you load
> 	l3backend-$DRIVER$
> Is there a way to set the used driver, or disable loading any of these
> backends at all?
 >
> pyxplot (not that I am really interested in it, it just breaks a lot of
> things in Debian and I want it fixed) is a dvi driver - it interprets
> dvi code generated with latex. Nothing load, plain latex.
> 
> Is there a way to say
> 	driver=ignore
> 	driver=pyxplot
> or similar?
> 
> Best
> 
> Norbert

The problem with saying 'disable the backend' is what then happens with 
things that *need* them, such as colour, rotation, hyperlinks, etc. The 
starting point in writing the backend code was that there are a small 
number of very well-established backends

- dvips
- dvipdfmx
- dvisvgm
- xdvipdfmx
- Direct PDF output

in use today, and that with a reasonable amount of effort one can 
support all of them. Currently, this list is hard-coded.

pyxplot isn't in TeX Live, so testing against it is going to be hard. 
Moreover, it doesn't seem to have documented \special support: I can't 
see anything about TeX in the manual I found.

You could try setting the backend to dvipdfmx, as that don't write a 
header, and if there are no other specials in use, won't actually show up.

     \PassOptionsToPackage{backend = dvipdfmx}{expl3}

would probably be the easiest way.

Joseph