Re: Units, font sizing, and zoom suggestion for CSS 3

Karlsson Kent - keka wrote:
> 
> As for em; I find it better to keep both with traditional definition
> *and* modern and widely spread computer typesetting systems like TeX,
> where "em" *is* defined as the width of M in the current font.  It is
> nice to have the same definition of things across systems; even for
> "relative units".  (If it has to me named differently ("wem"?) for a
> few CSS versions for compatibility reasons, then so be it.)

Earlier, on this list, Jan Roland Eriksson mentioned the following:

  http://css.nu/articles/typograph1-en.html

It says that the "em" has been changing over the years, starting with
Roman letters that were all capitals (e.g. M), followed by the
introduction of lower-case letters with descenders (e.g. p), and then
the advent of accents (e.g. ring above).

I don't know how much of that history is really relevant in this
discussion of the "em" unit, but I'm pretty sure that TrueType and
OpenType use a different definition of "em" than TeX. It seems to me
that TrueType is at least as important as TeX in the context of CSS
today.

I don't think that the width of the 'M' glyph is all that important, and
I'd rather not add "wem" to the CSS spec. I don't see an urgent need for
it, and we have too many units in CSS already.

Erik