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Re: Relative v absolute units (was Bobby inaccuracy?)

From: Charles McCathieNevile <charles@w3.org>
Date: Tue, 15 Jan 2002 15:11:23 -0500 (EST)
To: Rowan Smith <rowan@absolutely.co.nz>
cc: "Scarlett Julian (ED)" <Julian.Scarlett@sheffield.gov.uk>, <w3c-wai-ig@w3.org>
Message-ID: <Pine.LNX.4.30.0201151501330.20590-100000@tux.w3.org>
Trying to shine a light on what seems some fairly vague wording now...

A major reason for using relative units is that people change their font
sizes and window sizes to suit their own needs, and the design should cope
with that. So the way I understand it is "make sure that when the font size
is set to one half or three times, and the window is set to a small size (say
320x240) or a large size (at least as big as 1600x1200 if you can), the
content still works reasonably well".

In particular, having to scroll horizontally as well as vertically is a major
hassle unless people are using a real screen magnifier (i.e. for people who
don't find it sufficient to triple the font size it is easier to use a
special tool that handles having to move in two dimensions, but for a large
part of the population who just need the letters a bit larger, or have a
smaller screen, it causes problems).

As for passing Bobby, the problem with relying on a computer test is that
there may well be a bug in the program that misses something which a
thoughtful look over the code will reveal to many people.

The value of a tool like Bobby is it takes away a lot of repetitive work, and
can check things for people who haven't learned the intricacies of the code
produced by their editors. The risk is that people will think it is
infallible, whereas it is probably not quite as good as the people who
programmed it. (It may be much worse - it is not likely to be better).

So it is useful to track bugs in tools, and to look them up even if you don't
think you can fix them. At least you will know what the tool didn't do for
you, even if you can't do it either.



On Wed, 16 Jan 2002, Rowan Smith wrote:

  This line is the one that interests me (from Julian Scarlett's post on Tue,
  15 Jan 2002 10:08:52:

  Line 39: <div style="height: 280; width: 400; border: none; float: right">

  I'm still confused by this one - in this case absolute units are used to
  size the layer, and it passes Bobby AAA. Checkpoint 3.4 (priority 2) says to
  use relative units (ems or %), not absolute units. It then says "If absolute
  units are used, validate that the rendered content is usable".

  Can anyone elucidate what "rendered content is usable" means?


  -----Original Message-----
  From: w3c-wai-ig-request@w3.org [mailto:w3c-wai-ig-request@w3.org]On
  Behalf Of Scarlett Julian (ED)
  Sent: Tuesday, 15 January 2002 11:09 p.m.
  To: w3c-wai-ig@w3.org
  Subject: Bobby inaccuracy?

  I've just run a AAA Bobby test on a page and although it passed it included
  the usual user checks on colour and images conveying information ...

  Line 39: <div style="height: 280; width: 400; border: none; float:
  right"><img src="img/education.jpg" width="300" height="211" alt="Primary
  school children using modelling clay in a classroom">

Charles McCathieNevile    http://www.w3.org/People/Charles  phone: +61 409 134 136
W3C Web Accessibility Initiative     http://www.w3.org/WAI    fax: +1 617 258 5999
Location: 21 Mitchell street FOOTSCRAY Vic 3011, Australia
(or W3C INRIA, Route des Lucioles, BP 93, 06902 Sophia Antipolis Cedex, France)
Received on Tuesday, 15 January 2002 15:11:27 UTC

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