[luatex] \pdfstartlink ... isn't really a link.

[Paul Isambert]

Hello all,

This message addresses the pdfTeX kernel, but since LuaTeX is the pdfTeX's
future, I think it fits here.

I've just discovered that \pdfstartlink ... \pdfendlink doesn't create a link
when <action spec> is "user" instead of "goto". It simply creates an annotation,
whose /Subtype must be set to /Link (or anything else) in either "attr" or
"user". That's apparently a known fact since Heiko Oberdiek has written on the
pdfTeX list that "`user' must set /Subtype and /A"
(http://tug.org/mailman/htdig/pdftex/2008-August/007789.html).

However it is pretty confusing, all the more as the pdfTeX manual doesn't
mention it, quite the contrary: it says that <user action> is the action
performed when the _link_ is activated.

While that's no big deal once you know it (any insight on the historical reason
why?), it remains incoherent and umotivated (as far as I can see, at least). So,
for the sake of coherency & clarity of the future, wouldn't it be better to have
\pdfstartlink create a link no matter what, and perhaps another primitive
\pdfstartannot ... \pdfendannot that would do the same thing as \pdfstartlink
but without a /Subtype?

As for compatibility, code written up to know with such things as \pdfstartlink
user {/Subtype /Whatever ... } ... will produce an annotation with Subtype set
twice (once to /Link and once to /Whatever), but I've checked and Acrobat at
least doesn't mind, even if the two subtypes differ, and /Whatever wins, so
compatibility is preserved.

What, this, a feature request? Noooo, absolutely not.

Best,
Paul