W3C home > Mailing lists > Public > www-style@w3.org > December 1999

Re: CSS character width unit missing: an oversight, methinks?

From: Matthew Brealey <thelawnet@yahoo.com>
Date: Mon, 13 Dec 1999 05:02:34 -0800 (PST)
Message-ID: <19991213130234.12349.qmail@web901.mail.yahoo.com>
To: www-style <www-style@w3.org>
--- Bert Bos <bert@w3.org> wrote:
> Peter S. Linss writes:
> > In the Mozilla engine you can use the 'ch' unit.
> ie:
> > div { width: 80ch; }
> > 
> > This only works for certian horizontal
> measurements (I seem to remember
> > only widths, but I could be wrong) and only when
> there is a fixed width
> > font in effect for the formatting object,
> otherwise it is ignored.
> > 
> > I believe this has been proposed (at least
> informally) for CSS3. You can
> > take this as a formal proposal if you want...
> Yes, it has been proposed, but never in enough
> detail. What is clear
> is that there are two reasons for wanting this unit:
>    1. styling monospace text (including TTY and
> ideographs)
>    2. styling braille
> What is not clear is how to define the unit.

Since certain electronic typographical mechanism
define glyphs as rectangular boxes, each the same size
at a given font-size, achieving the appearance of
proportional spacing by negative kerning, it seems to
me that this approach leaves the door wide open for

The ch can be defined as the maximal width of a glyph,
since if it is defined as a mean figure, overlapping
would result at certain figures.

However, it seems that better might be:

wem (width of lowercase m)
wi (width of lowercase i)
ch (maximium glyph width)

>    c. ch is defined as the average width over
> certain (all?) glyphs
>    d. ch is defined as the width of a normal space
>    e. ch is defined as the width of a full-width
> ideograph
> If we take c-e, should the (actual) value of
> 'letter-spacing' be
> included in 'ch'? 

From Matthew Brealey (http://members.tripod.co.uk/lawnet (for law)or http://members.tripod.co.uk/lawnet/WEBFRAME.HTM (for CSS))
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Received on Monday, 13 December 1999 08:02:38 UTC

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