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Re: Inconsistent treatment of "em" and "ex" unit when used to specify "font-size"

From: Bert Bos <bert@w3.org>
Date: Fri, 30 Oct 2009 17:26:13 +0100
To: W3C Style List <www-style@w3.org>
Message-Id: <200910301726.13986.bert@w3.org>
On Friday 30 October 2009, Philip TAYLOR wrote:
> Bert Bos wrote:

> > On that last sentence of the quoted text (which is marked as an
> > issue in the working draft): The WG currently believes that the
> > text of CSS 2.1 ("In the cases where it is impossible or
> > impractical to determine the x-height, a value of 0.5em should be
> > used.") is still the best and can be inserted unchanged at that
> > point in the CSS3 module.
> I am a little unhappy with "or impractical"; does this not
> leave a rather large loophole for browser inconsistencies ?

A loophole, yes; a large one, I don't know. If I remember correctly, the 
existence of that loophole is indeed why that remark in red is in the 
Values and Units draft.

In general, we try to remove in the new modules all the vagueness that 
needs to be in CSS 2.1 to allow the specification to become a Rec. But 
not all fuzzy language can always be removed. We usually hope that 
competition in the market will push implementers to do the best their 
platform allows.

You think the only cases are possible and impossible, and impractical 
doesn't really exist?

> Philip Taylor
> --------
> [1] The Web team at Royal Holloway, University of London

  Bert Bos                                ( W 3 C ) http://www.w3.org/
  http://www.w3.org/people/bos                               W3C/ERCIM
  bert@w3.org                             2004 Rt des Lucioles / BP 93
  +33 (0)4 92 38 76 92            06902 Sophia Antipolis Cedex, France
Received on Friday, 30 October 2009 16:26:50 UTC

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