On Sat, 5 Jun 2004 05:37:20 +0000 (UTC), "Jukka K. Korpela"
<jk******@cs.tu t.fi> wrote:
Neal <ne*****@yahoo. com> wrote: The "em" in CSS is not identcal to the print em.
It is the same concept: the size of the font.
It is the default
size of a typical character after any inhereted adjustments.
I wonder where all this misunderstandin gs about em stem from.
Yea; Me to gets astonished at some of the interpretations that pops up
every now and then.
The height of a typical character is _much_ smaller than em
Well; to the naked eye yes, but...
The majority of fonts designed within the previous millennium are
designed to fit on a lead block destined to be set in a printing frame.
In order to facilitate easy typesetting, all lead blocks used in a
printing frame has to be of the same height (for western alphabets that
is).
Following that, the minimum height of a lead block, intended for use in
traditional typesetting, must be as high as required to "house" any one
single character in the font in use when each and every character in
that font is placed on a common baseline.
So the net result is that 1em becomes equal to the height of the lead
block required to "house" any one character in any given font design.
Note; this includes height to "house" character decenders just as well
as diacritical marks, should they be designed parts of the font at hand.
The definition of one 'em' in CSS1 is derived from traditional
typesetting and I have at one time been in live "person to person"
discussion with Haakon on this subject and there is no doubt that the em
definition in CSS1 has its roots in the minimum required height of a
lead block, as used in traditional typesetting for prints.
Further; it can be empirically proven that font designers as early as
Claude Garamond (hundreds of years back) was thinking along the same
line.
The "Plantin Moretus Museum" in Antwerp, Belgium, has a large set of
Claude Garamond's original design work in storage. One very specific
item there is the Garamond definition of what we would call an "em dash"
which just "happens" to be designed to fit the full width of a _square_
lead block with a block height equal to all other block character casts
available.
Naturally we can also find an "en-dash" in the Garamond font and from
the best judgment I was able to make on site, the Garamond en-dash is
very close to half the width of the em-dash.
Given the fact that there is European historical roots available for the
definition of one 'em' I would, provocatively, move on to say that any
saying to the effect that "1em is equal to the width of letter 'm' or
'M'" is nothing but Bullshit of Anglo-Saxon origin :-)
--
All the best...
Rex
P.S. Why did Knuth fall for that "em is letter 'm' width" thingy in
LaTex?