[NTG-pdftex] Re: [pdftex] Math Pdftex extensions ?

Paul Pichaureau paul.pichaureau at alcandre.net
Sun Jan 15 22:58:27 CET 2006

Le dimanche 15 janvier 2006 à 20:11:02, vous écriviez :

HH> Paul Pichaureau wrote:

HH> if you can point out the specific things that you want to be supported,
HH> the pdftex dev team can look into it

HH> after all, pdftex is also a playground for new tex functionality (within
HH> reasonable bounds)

Well, that's a good question... I do know that some terrific ideas, at
first glance, could be a nightmare to implement. But this is some
point I find interesting:

1) Of the following document, I shall retain some ideas


The extended semantics of \mathaccent is a good idea. It could
extend the possibilities of TeX significatively. I think you could
create a new kind of accent (let's say \exmathaccent) for that.

The possibility to switch in cramped styles could be nice for testing
purpose, although useless for most users. The generalized radical is
nice also... but of limited interest, isn'it ?)

2) Under accents are waited by many users for a long time. The problem
remain the lack of a new \skewchar character to tweak the placement of
the underaccent.

Moreover, extensible underaccent could be a nice improvement in term
of typesetting quality. With that, it should be able to design
beautiful \under and \overbrace (the actual horizontal braces of TeX are
ugly, IMHO).

I'm an neophyt in these matters, but I think, if an equivalent to the
existing \skewchar is defined, the rest will not be so difficult to

I'm aware the existing math fonts will need to be tweaked, but I think
this feature deserves many efforts!

3) A point cited by Knuth is a deficiency in the fraction typesetting
algorithm: the minimal distance between the numerator and the
denominator of a fraction is related to the rulethickness of the
mathematical fonts. That could lead to ugly results if the font is
very bold (for example Utopia Bold).

The perfect solution consists in the introduction of a new fontdimen
(let's say fontdimen23). But there is a risk of incompatibility, if
someone has already used these fontdimen. A new TeX dimension
parameter should be introduced here.

4) The last point I want to cite now is the spacing of formula in
script and scriptscript style. For a unclear reason, in script style
TeX doesn't introduce any spaces between symbols as it does in text
and display style.

This is good for computer modern, which is legible at all size. But
today, we use scalable fonts which are less legible than CM in small
sizes. I think the possibility to switch on the formula spacing in
script and scriptscript style should lead to a significant improvement
of legibility for some fonts.

Well, I have many others ideas. But I present here the most useful/the
easiest to implement... I hope ! :-)

HH> Hans

  Paul Pichaureau                            www.alcandre.net

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