W3C home > Mailing lists > Public > www-font@w3.org > October to December 1999

Re: position of baseline relative to em square

From: David Lemon <typenerd@slip.net>
Date: Sat, 4 Dec 1999 09:20:21 -0800
Message-Id: <l03130301b46ef998a5af@[209.209.14.248]>
To: erik@netscape.com (Erik van der Poel)
Cc: www-font@w3.org
I wrote:
> But for optical and typographic purposes,
> nominal ascent and descent are useful for glyph placement, and should not
> be tied to bounding box height, depth or width.

and Erik van der Poel asked:
> When you say "nominal ascent and descent", do you mean the ascent and
> descent that add up to the em square height?

Yes - the typographic ascent and descent values stored in the OS/2 table.
As noted before, Adobe sets these to sum to the em height, but they may
only approximate the em height in some other fonts. BTW, similar values can
be found in the FOND resource of Macintosh fonts, which may not have an
OS/2 table.

Nick Nussbaum noted:
> My recollection from earlier font days was that there were a number
> of fonts which were originally designed for domestic use [and] had
> accents tacked on when the font was globalized.

That sounds quite plausible. But I haven't seen a pattern of difference in
cap height and accent placement between fonts from, say, the American and
German branches of Linotype.

> Is there any assumption that setting with extra lead values will not
> cause descender/accent overlaps.

While leading is usually helpful whether or not accents are present, it
certainly does eliminate the chances for descender/accent collisons which
are possible in "solid" accented text. This doesn't mean the extra leading
is always required; it just means it makes things safe. With attention,
*short* pieces of text can often work well with "negative leading" - i.e.
less than baseline-to-baseline linespacing. This is quite common in display
advertising and labelling.

- David Lemon
Received on Saturday, 4 December 1999 12:22:07 UTC

This archive was generated by hypermail 2.4.0 : Friday, 17 January 2020 22:37:30 UTC