Re: "em" should be horizontal, "ex" vertical

Walter Ian Kaye (walter@natural-innovations.com)
Mon, 11 Aug 1997 04:23:02 -0700


Message-Id: <v03102805b014a57fa1eb@[205.149.180.135]>
In-Reply-To: <1340824450-78650621@battersea.indx.co.uk>
Date: Mon, 11 Aug 1997 04:23:02 -0700
To: <www-style@w3.org>, <www-html@w3.org>
From: Walter Ian Kaye <walter@natural-innovations.com>
Subject: Re: "em" should be horizontal, "ex" vertical

At 11:12a +0100 08/11/97, Clive Bruton wrote:
 > Peter Flynn wrote at 11/8/97 10:59 am
 >
 > >> While that's a good definition, typesetting practice /never/ uses "em"
 > >> as vertical measurement; an em is a horizontal measurement only, and an
 > >> "ex" is the vertical measurement.  This makes measurements based on
 > >> fonts size work with compressed an/or fat fonts.
 > >
 > >This is incorrect: pica ems are used for page depth and line spacing
 > >almost universally in the Anglo-American world. When did you last see
 > >a comp's spec specify print-area height in "ex"s?
 >
 >
 > Correct, the definition of an "em" is a *square* of any given body size,
 > ie 9pt*9pt, 24pt*24pt, 72pt*72pt are all ems.

And here I thought an em was a square the width of an uppercase "M".
Silly me.

 > The correct term for a 12pt
 > em is a *pica* em as pointed out, an em is a relative unit.

I've never heard of a "pica em" -- only just "pica" (1/6 of an inch), and
picas are indeed used for both horizontal and vertical.

__________________________________________________________________________
  Walter Ian Kaye <boo_at_best*com>    Programmer - Excel, AppleScript,
          Mountain View, CA                         ProTERM, FoxPro, HTML
 http://www.natural-innovations.com/     Musician - Guitarist, Songwriter