l3backend: adding new DVI specials?

[Joseph Wright]

On 19/02/2020 10:08, Norbert Preining wrote:
> Hi Joseph,
> 
>> The problem with saying 'disable the backend' is what then happens with
>> things that *need* them, such as colour, rotation, hyperlinks, etc. The
> 
> I understand, but none of them are interpreted, only "color" special is
> interpreted by pyxplot. It does not contain arbitrary TeX documents,
> just minimal latex document with a page containing the plot.

Sure, but starting from the 'writing support macros' end we want to have 
a known set of functions. At present, I can't even find information on 
what type of colour specials pyxplot supports.

>>      \PassOptionsToPackage{backend = dvipdfmx}{expl3}
> 
> Maybe I do it wrong, but that does not work:
> 	\PassOptionsToPackage{backend = dvipdfmx}{expl3}
> 	\documentclass{article}
> 	\begin{document}
> 	Hello World
> 	\end{document}
> still contains the dvi special for loading l3backend-dvips.pro

I realised that after I sent it: you'd need to explicitly load expl3. 
Probably best just to

     \RequirePackage[backend=dvipdfmx]{expl3}

although you could force in various other ways.

Joseph