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Re: Sizing

From: David Dorward <david@dorward.me.uk>
Date: Sun, 17 Sep 2006 12:28:48 +0100
To: www-style@w3.org
Message-ID: <20060917112848.GA4865@us-lot.org>

On Sun, Sep 17, 2006 at 01:07:32PM +0200, Axel Dahmen wrote:

> What is rendered on screen always varies depending on the screen
> resolution.  Units like "pt" are never displayed in their correct
> sizes.

Most systems are not calibrated correctly so the system can't convert
points to pixels accurately (there may also be browser bugs
involved). I don't see how any change to the CSS specification could
work around this problem.

> Similar for printing: "px" unit rules are never printed in the
> printer's resolution.

They shouldn't be:

   Pixel units are relative to the resolution of the viewing device,
   i.e., most often a computer display. If the pixel density of the
   output device is very different from that of a typical computer
   display, the user agent should rescale pixel values.
 
     -- http://www.w3.org/TR/CSS2/syndata.html#value-def-length

> The new "scaling" rule should only allow
>   * percentage values
>   * a factor to set a fix scaling, using length units:
>       something like
>          "300pt" => 300 pixels equal one Point
>          "500cm" => 500 pixels equal one Centimeter

This seems to be moving responsibility for defining the DPI of the
system from the system administrator (who has a chance of configuring
it correctly) to the document author (who, in the case of the WWW at
least, hasn't a hope of doing so).

-- 
David Dorward                                      http://dorward.me.uk
Received on Sunday, 17 September 2006 11:28:58 GMT

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