[metapost] luamplib

Hans Hagen pragma at wxs.nl
Fri Nov 12 21:39:37 CET 2010

On 12-11-2010 7:32, Dan Luecking wrote:

> As I said, these things would probably be obvious to an expert.
> It is clear from the results that luamplib.pen_info is nil, so
> neither of these alternatives was done, and I don't know how to
> do either of them. Mostly my solution was a lucky guess.

I synced the tex live repos and looked into the file and recognize bit 
and pieces. However, it is a patched copy of the original. It looks like 
the module itself is called luamplib and there is no pen_info defined in 
that namespace (it is a function in the mplib namespace and would be in 
the luamplib namespace if that was a synonym). So, it's simply a problem 
that follows from the fact that instead of using the original 
implementation (and extending that if needed) a copy was taken.

Now, to come back to the remark about an expert, I probably could have 
figured it out easily given that I'd installed latex etc etc which is 
not the case. Also, I already have the original to maintain.

> One assumes that luamplib.flush is somehow doing the equivalent
> of recursing through currentpicture and examining the
> equivalent of penpart. However, I don't know how to extract the
> transform components of an elliptical pen in MetaPost. I'm
> guessing mplib has something that regular MetaPost (at least
> in version 1.2x) lacks.

Indeed, the lib gets a lua table that has a representation of the result 
and it converts that to pdf. In the process it uses pen_info and there 
the test fails, hence no pen data is processed. Mplib does not have 
anything additional.


                                           Hans Hagen | PRAGMA ADE
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