Verbatim / prettyprinting in mkIV

[Matthijs Kooijman <matthijs@stdin.nl>]

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Hi all,

I've been struggling with verbatim printing in MkIV for a while now and found
some confusing things. I did finally get things working, but after quite some
effort. I'd like to hear if my conclusions are correct, perhaps I can put them
on the wiki then.

I was trying to set up some custom pretty printing scripts, using lua (since
I'd rather not learn complete tex scripting :-p). Looking at the files in
/usr/share/texmf/tex/context/base and the wiki (Verbatim_text talks about
verb-foo.tex files), I created a file called verb-foo.lua. I put this beside
my document at first, and then in /usr/share/texmf/tex/context/base when it
did not work, but neither worked. I tried setting things up as follows:

\installprettytype [FOO] [FOO]
\definetyping[FOO][option=FOO]

\startFOO
  blub
\stopFOO

Trying to trace the code, I worked out things should work as follows:

\installprettytype sets the "evalue" \??ty\??tyFOO to point at FOO
\definetyping call \setupprettiesintypeFOO, which finds looks up the above
evalue, finds FOO and then turns that into verb-foo and calls
\ctxloadluafile{verb-foo}{}. This sets up the buffers.visualizers.foo value in
lua. When actually starting a typing environment, dodotypeA or dodotypeD call
buffers.hooks.flush_line, which in turn calls
buffers.visualizers.foo.flush_line.

The above didn't happen for me, so I tried manually loading the lua file using
\ctxloadluafile{verb-foo}{}. After this, things started working for some reason.

When looking closer and installing some \writestatus lines in core-ver.mkiv, I
found that \setupprettiesintype was never actually called! Closer inspection
showed that the entire core-ver.mkiv is never loaded when running "context
--make". However, there is a second file, buff-ver.mkiv which closely
resembles core-ver.mkiv and which is loaded. An important difference, however,
is that buff-ver loads pret-foo instead of verb-foo (or rather, uses the value
of \f!prettyprefix, which is set to "pret-" in mult-sys.tex).

Renaming my lua file to pret-foo.lua made context find it exactly as it
should, also when putting the file next to the main document.

So, my main question was, are the verb-*.lua and core-ver.text files still
used in any way? I just checked the minimals tree, and found out they have
been removed already (but I didn't have -d in my rsync commandline to actually
remove them). Looking at the previous version I was running (2009.05.20 beta)
it seems that this change was actually pretty recent, so I mostly created this
confusing situation by upgrading today (because my verbatim file was not
properly loaded). I'm not so sure why it was not working before then, but at
least it is working now.

Heh, this is what you get when you write an email while you are still trying
things out. All this buildup to get to a question, when the question is not
even relevant. As for another relevant question: Is my analysis of how things
are supposed to work correct? Then I might put something like it on the wiki.

Also, it seems that \ctxloadluafile does not give an error when the file was
not found. If it would have, things would probably have been a lot easier. Is
there any compelling reason to make it fail silently?

Gr.

Matthijs

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