l3backend: adding new DVI specials?

[Zdenek Wagner]

pá 14. 2. 2020 v 10:57 odesílatel David Carlisle
<d.p.carlisle at gmail.com> napsal:
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> On Fri, 14 Feb 2020 at 09:49, Zdenek Wagner <zdenek.wagner at gmail.com> wrote:
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>> It's a long time when I used DVI last time but if I remember the
>> specification well, if a DVI driver does not understand a \special, it
>> should emit a warning and ignore it.
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> Yes but if you wrap in a regression test that's checking no new warnings occur, then
> "emit a warning and ignore" can still  cause tests to fail, which is probably what happened here.
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Yes, but as was already mentioned, pdftex can distinguish between a
PDF mode and a DVI mode but cannot guess the DVI driver. The
regression test must follow specification and select the DVI driver
used further in the test. I am afraid there is no other possibility.
XeTeX invokes xdvipdfmx explicitly so it can know which driver is
used, it is not the case of pdftex in the DVI mode.

> David
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Zdeněk Wagner
http://ttsm.icpf.cas.cz/team/wagner.shtml
http://icebearsoft.euweb.cz