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Date:         Tue, 15 Sep 2015 20:51:29 -0400
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From: Bruno Le Floch <blflatex@GMAIL.COM>
Subject: Re: interface for test on driver being used
To: LATEX-L@LISTSERV.UNI-HEIDELBERG.DE
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Envelope-To: <rainer.schoepf@GMX.NET>
Status: R

On 9/15/15, Joseph Wright <joseph.wright@morningstar2.co.uk> wrote:
> On 15/09/2015 09:12, Alexander Grahn wrote:
>> Good morning,
>>
>> There is a number of functions in the new l3sys package for testing the
>> current engine, but I am still missing a public interface for testing
>> the driver. The l3drivers package internally uses some mechanism to
>> distinguish between pdfmode, dvips, dvipdfmx and xdvipdfmx. Will there be
>> such a testing be included in the public interface of expl3 one day?
>>
>> Currently, I am still using a combination if the `ifpdf' package and the
>> \*_if_engine* functions for the purpose of driver detection.
>>
>> Kind regards,
>> Alexander
>
> Hello Alexander,
>
> Adding material to l3sys is on the 'to do' list but there are several
> things there for 'soon'! I can certainly look to add a DVI/PDF test
> (definitely one to do).
>
> In terms of drivers, we could/should move that code to l3sys anyway. The
> question of to what extent any code of this form should be outside of
> the kernel is tricky: for say drawing I can imagine something akin to
> pgf's system layer with a low-level public interface on top (there are a
> limited number of well-defined operations). For what you want (I'm
> guessing) that's not so clear: I've not looked in detail but I assume
> the entire set up for movie inclusion is highly system-dependent.
>
> Joseph

I think it makes sense indeed to provide a conditional for the driver
in use.  However, we should provide wrappers for most operations
(drawing, graphics inclusion, color handling) and explicitly advise
people to use these wrappers rather than the driver conditional.
Movie inclusion is a bit special and may be beyond what we want to
provide wrappers for.  But maybe it could make sense to include a
trimmed-down version of media9 as a team-supported package?

Bruno