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Re: [css3-values] Unit normalization and types

From: David Woolley <forums@david-woolley.me.uk>
Date: Sat, 28 Mar 2009 14:14:12 +0000
Message-ID: <49CE30B4.1080807@david-woolley.me.uk>
To: "www-style@w3.org" <www-style@w3.org>
Giovanni Campagna wrote:

> I ask the question again "how the UA *or the system* can convert
> pixels to centimeters, since they have no knowledge about the diagonal
> of my monitor?". Obviously the UA can just assume 1 in = 96 px = 2.54
> cm and convert like that, but the meaning of lenght is distorted. Even
> if the system knows the output resolution, it will not know the
> scaling done by the monitor.

Because the monitor description, which modern systems should be able to 
obtain by plug and play, tells the GUI the physical size of a pixel, and 
even if this information is incorrect, the user agent assumed size of a 
pixel will have the same proportionate error as the size it actually 
uses to display a cm, so will cancel out in the round trip from px to px.

David Woolley
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Received on Saturday, 28 March 2009 14:15:25 UTC

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