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Re: font-size and accents, again

From: L. David Baron <dbaron@fas.harvard.edu>
Date: Mon, 22 Nov 1999 13:36:45 -0500 (EST)
Message-Id: <199911221836.NAA19277@is03.fas.harvard.edu>
To: erik@netscape.com, fahrner@pobox.com
Cc: www-style@w3.org
On Fri, 19 Nov 1999 10:10:07 -0800, Todd Fahrner (fahrner@pobox.com)
wrote:
> 
> At 8:57 AM -0800 11/19/99, Erik van der Poel wrote:
> 
> >Just to confirm, when you say "when set solid", you mean making the
> >distance from baseline to baseline equal to the em, right?
> 
> Yes. CSS-2's definition of font-size [1] uses this semi-circular 
> language: font size is the size the font says it is.

This is where I disagree.  I think this is because I picked up a
non-CSS definition of set solid from Roland Eriksson (I can't find a
reference - it may have been through email discussion - please correct
me if I'm wrong): the term "set solid" originates from typesetting in
metal, where pieces of brass were used to create leading [2].  If no
such metal were used, then the text is "set solid."  Since the
characters on the glyphs can't extend past the rectangles that those
characters are on, glyphs in adjacent lines can't overlap when set
solid, but they can touch.  Since CSS makes no further attempt to
define "set solid," and defining it in terms of line-height and
font-size would be circular, this is the only adequate definition I
know.

Also, I'd like to clarify one point about my article on font sizes
[3].  Although I would like to see font-sizes supported according to
the spec (since this makes authors' suggestions more portable, as Erik
mentioned in [4]), I think it's more important that there be a
consistent solution.  One of the main points I wanted to make is that,
if we accept that font-size does *not* refer to the outermost extent of
the glyphs, then user agents should be consistent in their treatment of
line-height, backgrounds, and 'em' units.

I would propose the following solution for handling fonts that are
bigger than they claim to be: the 'em' unit should be the actual value
of the font-size as stated by the font, but scaling factor units for
line-height and the height used for backgrounds (and padding and
border) on inline elements should be based on the "true" font-size
(including all the height of the glyphs).  Note that in this solution
'em' units on the line-height property differ from scaling factors in
more than just how they inherit.  I believe this solution is close to
current practice (it would correspond to O O C O in the table in [3],
although my test did not test 'em' units on line-height, which would in
this solution be treated differently from scaling factors).

-David

> [1] "The font size refers to the size of the font from baseline to 
> baseline, when set solid (in CSS terms, this is when the 'font-size' 
> and 'line-height' properties have the same value)."

 (where did you get this quote?)

[2] http://css.nu/articles/typograph1-en.html#Ch25
[3] http://www.fas.harvard.edu/~dbaron/css/fonts/sizes/
[4] http://lists.w3.org/Archives/Public/www-style/1999Nov/0111.html

L. David Baron    Sophomore, Harvard (Physics)    dbaron@fas.harvard.edu
Links, SatPix, CSS, etc.     <URL: http://www.fas.harvard.edu/~dbaron/ >
WSP CSS AC                      <URL: http://www.webstandards.org/css/ >
Received on Monday, 22 November 1999 13:36:47 GMT

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