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Re: cross posted form IG

From: Alan J. Flavell <flavell@a5.ph.gla.ac.uk>
Date: Sun, 6 May 2001 19:53:10 +0100 (BST)
To: Matt May <mcmay@bestkungfu.com>
cc: W3c-Wai-Gl <w3c-wai-gl@w3.org>
Message-ID: <Pine.OSF.4.21-pb.0105061931270.10269-100000@a5.ph.gla.ac.uk>
On Sun, 6 May 2001, Matt May wrote:

> First, px _is_ absolute.

Well, px _is_ problematical, I'm not disputing that...

It isn't an "absolute length unit" in the CSS sense, however.

> It's font height in number of pixels.

Not quite.  It's _supposed_ to be roughly normalised to "reference
pixels" of 90ppi (pixels per inch), so it's intended that those with
72ppi displays and those with 150ppi... displays would still be seeing
about the same physical size as each other.  Unfortunately, even this
isn't implemented in mainstream browsers, yet.

But this is meant to adapt only for different _display_ properties,
not for different _user needs_.  It would be apt for example in a
projection system designed to be viewed by a room full of users, where
everyone inevitably has to view the same settings.  It's quite
inappropriate for a personal viewing system.

> The major issue is that pixel-sized fonts can't be resized using the font
> tools in the browser.

If the browser does what CSS asks of it, then clearly you have a
problem; but any decent browser ought to have SOME ability for the
user to take control when the author's presentation isn't accessible
to them.

> So if I have my browser's font set to "Largest", and
> you have your fonts set to "8px", what I'll see is 8px no matter how I try
> to resize.

This is so for NN4.* versions, for example. Turn off CSS and the
problem is solved.  Of course you then lose all the other features of
CSS, but a properly-designed page doesn't absolutely rely on CSS for
getting its message across, and when the CSS is doing more harm than
good, the reader needs to take the inevitable action.  So if the page
falls apart, it's not the fault of the reader.

Take a look at (an article that I'm not uncritically supporting in
every detail, but it's interesting to see it at work):
http://www.alistapart.com/stories/journey/ - with and without CSS.

It's visually very different - but the content is there, either way.

> A user's only theoretical way around this would be to use a
> client-side style sheet, which is still unsupported in most browsers;

Unfortunately, this cannot actually work in general, because the
CSS-styled page is liable to use all kinds of specificities that will
take priority over the more generic settings that a client stylesheet
can set.  Only if the author has been a good guy and used relative
sizing techniques (percent, em/ex, larger/smaller, inherit) is the
cascade going to be susceptible to user influence in that way.

To overrule authors who have created high-specificity absolute-sized
font sizing, you need stronger medicine than just tossing a user
stylesheet into the CSS cascade, if I'm not mistaken. 

> There are some other minor issues with px, like it's not aware of the size
> or resolution of the display.

The CSS specification says that it needs to be.  It usually isn't yet,
but you're right, it does need to be.  However, that still takes no
account of user needs - only of platform properties.

best regards
Received on Sunday, 6 May 2001 14:53:30 GMT

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