Joe Armstrong <>
Mon May 24 16:18:03 CEST 2004

On Fri, 21 May 2004  wrote:

> A propos the erlguten pdf stuff. 
> One, have you(Joe and whoever else is on the 
> project) considered doing xsl-fo support?

  I considered it and then rejected the idea.

  I wanted to go from XML markup -> PDF 
in one step. This is in itself a difficult problem
adding yet another intermediate language make it even 
more difficult.

  I want ErlGuten to *create* the PDF and no other program - that wall
I'll get exactly what I want and nothing else.

  If I transform  to xsl-fo and then let some  other program turn this
in PDF then I loose this control  - and if things go wrong and I don't
get the results I want it will be *very* difficult to fix.

  << this  is just a special  case of Joe's theorem,  namely, "If more
than 2 open source projects  are combined into one project then you'll
spend  all  your time  figuring  out why  the  code  in the  different
projects is broken and zero time on the original problem >>

  It turns out  that PDF is pretty easy to produce  (just read the 673
page PDF  manual, oh  and 890  pages of postscript  and a  few hundred
pages on fonts - thats all you need :-) - then you can do whatever you
want.  My goal  was to steer the placement of pixels  on paper down to
single pixel  resolution -  this is  pretty easy -  I think  going via
xsl-fo would just complicate matters.

> Two, if not maybe might want to look at 
> it struck me as 
> an idea to base erlguten on pdml and then 
> allow extensions to do more advanced stuff. 

pdml is much simpler that erlGuten - so I guess I "easily [1]" transform
pdml to ErlGuten and thence to PDF.

> Basically i was thinking that might be an 
> idea given PDML being implemented in php, 
> and YAWS support for php. one of the hotter 
> areas for pdf generation being online print 
> on demand generation.

  What is  Yaws support  for php?  - are we  looking for  volunteers to
write a php interpretor in erlang? << actually this would be great fun,
there is no reason to imagine that a php interpretor implemented in
Erlang would be slow. Anybody got a PHP yacc grammar? >>



  [1] Easily is meant in the sense of - "I haven't written a program that
actually does this but it's probably not *impossibly* difficult."


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