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Re: position of baseline relative to em square

From: Nick Nussbaum <nickn@seanet.com>
Date: Tue, 30 Nov 1999 21:18:10 -0800
Message-ID: <000201bf3bc6$831f6760$6209070a@nickn0>
To: "Greg Hitchcock" <gregh@microsoft.com>, <typenerd@slip.net>, <erik@netscape.com>
Cc: <www-font@w3.org>
Shouldn't it include extra leading ?
I can't check right now because I'm home offline but is the extra leading
considered part of the
the baseline to baseline? Is baseline to baseline considered an em square in
your fonts?<www-font@w3.org>


Finally  the sort of discussion I'd hoped for from this list. :-)


----- Original Message -----
From: Greg Hitchcock <gregh@microsoft.com>
To: 'David Lemon' <typenerd@slip.net>; <erik@netscape.com>
Cc: <www-font@w3.org>
Sent: Tuesday, November 30, 1999 2:01 PM
Subject: RE: position of baseline relative to em square


> In general David is correct here. The Windows metrics otmAscent and
> otmDescent map to the sTypoAscender and sTypoDescender in the OS/2 table
of
> the font. Typically otmAscent maps to the top of the l/c f (or sometimes
d)
> and the otmDescent maps to the bottom of the l/c g (or sometimes p) This
is
> usually very close to the em, although not quite. I believe that this
> difference is sometimes caused by the bevel on the hot-metal slug that was
> used for strengthening. One could reasonably take the difference between
> otmAscent and otmDescent and evenly divide it above and below to determine
> the baseline in the em.
>
> GregH
>
> -----Original Message-----
> From: David Lemon [mailto:typenerd@slip.net]
> Sent: Tuesday, November 30, 1999 8:15 AM
> To: erik@netscape.com
> Cc: www-font@w3.org
> Subject: Re: position of baseline relative to em square
>
> At 11:49 PM -0800 11/29/99, Erik van der Poel wrote:
> > However, if CSS wants us to center in terms of the em square, we would
> > need to know where the baseline lies in the em square.
> >
> > As far as I can tell, neither the Windows APIs nor the TrueType file
> > give us this info. Is this true?
>
> Although not very clearly specified, the (absolute values of the)
> WindowsTypographicAscent and WindowsTypographicDescent in the OS/2 table
> should sum to the em square height, positioning the baseline in the em
> square. I can't guarantee the general case, but can state that Adobe's
> OpenType fonts do exactly that.
>
> - David Lemon
>
>
Received on Wednesday, 1 December 1999 01:34:41 GMT

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