Re: [NTG-pdftex] images in formats

27 Jun 2007


      2007/6/27, David Kastrup :
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"Martin Schröder"  writes:
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2007/6/27, David Kastrup :
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For example, preview-latex uses mylatex.ltx to dump the state of the
TeX at \begin{document} time.  Not allowing any image references (like
in \savebox commands) before that point of time is a rather brutal
restriction.
Why do you need it
What?  preview-latex?  mylatex.ltx?
\savebox
...
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and what do you gain by using \savebox?
Uh, it is _there_.  For a reason.  Saying that it (and similar
functionality) should not get used anymore is creating a rather sordid
restriction and backward incompatibility.
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The speed increase is most likely minimal
The speed increase of what is most likely minimal?  Of dumping a
format with the preamble?  Absolutely not.  It is very relevant in
preview-latex, for common editing work on single formulas easily a
factor of 5.  And we are talking about an interactive editing task and
its response time here.
The speed increase of using \savebox.
...
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and the document needs to read the image anyway -- unless you want
to dump fragments of pdf code into the format.
In DVI mode, a pointer to the image gets dumped in the form of a
special.  A similarly sufficient amount of information would have to
get there in PDF mode.
...
If we expanded the dvi model we would dump the meta information
about pdf things and then undump them later. This needs code for
dumping and undumping this meta information. And
\immediate\pdfximage would still fail.
[...]
...
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Don't forget: pdfTeX is one-pass, while TeX->dvips is two-pass.
Where is the relevance?
It was not designed with making two-pass-like solutions (which we are
discussing here) working, instead the two passes are intermingled. The
"sufficient amount of information" aka "meta information" is most
likely not in the code in one piece and there is currently no way to
dump and undump that. And a proper solution would not only handle
\pdfximage, but also \pdfobj, \pdfxform, ...

Best
   Martin