Re: [Groff] Font Composition

[Werner LEMBERG]

> 1) The UnderlinePosition and UnderlineThickness values from the
>     afm files are discarded by afmtodit.  There is nothing
>     corresponding to the in the groff devps font files.  How is
>     groff then expected to provide proper underlining to text?

Of all output formats groff is supporting, only PS has support for
font-based underlining.

> 2) Can groff `compose' fonts, so to say?

Yes.  Check the .fspecial request.

>     If we have these fonts, is there any way to set up a font-file
>     so that groff mainly uses characters from the regular font, and
>     switches to another font (which will be intentionally visually
>     compatible with the main font) when it needs ffi, or small caps,
>     or old-style figures?

Assuming that font `foo' contains the normal fonts, and font
`foo-sc' the small caps glyphs, it would make sense to say

  .fspecial foo-sc foo

so that glyphs not contained in `foo-sc' are taken from `foo'.

> 3) Another type of composition may be useful.  As opposed to the
>    `design-time' composition discussed in the previous point, this
>    is `run-time' composition.  This involves providing groff with a
>    certain set of instructions that cause it to render *every*
>    character of a font in a slightly different way, keeping the
>    metrics the same, or differing in a systematic way.

It's always problematic to add features to groff just for the sake of
PS output.

>    In effect, the additional instructions will be drawing
>    primitives, but should be made general to permit, for example,
>    overprinting.  This technique can be utilised to effect using
>    only that most expressive of mediums---PostScript, but can be
>    used to wonderful effect for generating special effects such as
>    strikethrough, underline, and pseudo-boldify/italicise reliably,
>    and without any of the trickery macro-packages must employ to get
>    around to it.  It can also be creatively used for many more
>    effects.

Well, groff already has some features for that: Read the section
`Artificial Fonts' in the groff texinfo manual.  In general, I
consider such features as bad.  It is against good typographic
tradition.

If you really need such features it should be straightforward to
provide some PS macros, but I strongly oppose to add this directly to
groff since it won't work with other devices.


    Werner