[texhax] Combining symbols (vertical placement of characters)

[Reinhard Kotucha]

Uwe Lück writes:
 > At 20:32 29.12.08, John Palmer wrote:
 > >On Monday 29 December 2008 03:54:11 Daniel Freedman wrote:
 > > > position a bullet over the arrowhead
 > >
 > >I have done this sort of thing by using \raisebox for vertical and \kern for
 > >horizontal movement, but there must be a more robust and elegant way, so I'll
 > >be interested in other replies !
 > 
 > If you really want to compose (running just TeX) new glyphs from existing 
 > ones, you should know how the latter were designed (and how they are coded 
 > in METAFONT), in terms of font dimensions, cf. TeXbook p. 433/447; or of 
 > the height of `(' (\mathstrut) ... and in your macros, you should refer to 
 > these (\fontdimen, ...) [I can't tell details here]. Referring to such 
 > dimensions would be better than trying various numbers ... Replacing the 
 > arrowhead with a bullet, you should refer to the height and width of the 
 > box enclosing the diagonal stroke and to the width of the bullet and the 
 > height of its center (I guess it's axis_height according to TeXbook p. 
 > 447). Don't forget \mathpalette ...
 > 
 > But John: I wonder whether you are asking about creating new glyphs or just 
 > about placing one character over another. The latter task usually requires 
 > dimensions of enclosing boxes only; it can be performed through one-column 
 > ``tables'' (\oalign) or through the \accent primitive (depends ...). Are 
 > you thinking of specific examples that have bothered you?

There is nothing wrong if new symbols are composed with \kern and
\raisebox.  Everything which works is fine.  However, the most
reasonable approach is to check whether a particular symbol exists
already: 

  http://www.ctan.org/tex-archive/info/symbols/comprehensive/symbols-a4.pdf
  http://www.ctan.org/tex-archive/info/symbols/comprehensive/symbols-letter.pdf

This should always be the first step.

Regards,
  Reinhard

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