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Re: Making pt a non-physical unit

From: Allan Sandfeld Jensen <kde@carewolf.com>
Date: Thu, 14 Jan 2010 10:14:15 +0100
To: www-style@w3.org
Message-Id: <201001141014.15836.kde@carewolf.com>
On Wednesday 06 January 2010, Giuseppe Bilotta wrote:
> If a fixed px/pt ratio is chosen as the preferred solution for the
> mess of mixing absolute and relative units of measure, I would rather
> see px defined in terms of pts (and thus of inches) as suggested
> elsewhere in this thread, rather than the other way around, and have
> the UAs query the display dpi to adjust for the physical px size.
> 
Unless it has changed, I think this is what WebKit does but only for high DPI. 
The problem is that small fractions px will scale images badly. So for low DPI 
px is 1, for high DPI px is defined from pt. Since the requirement for high 
DPI is 300, it essentially means: For printing exact sizes are used.

I can add another quirk from KDE (also KDE WebKit Part). While pt is defined 
with a static DPI 96 when used in CSS. We use real DPI when font-sizes are 
specified in KDE dialogs. This means the default font size of 10pt or 12pt is 
scaled using real DPI. Thus webpages that doesn't specify absolute sizes are 
scaled depending on screen resolution. A trick for web-pages is then to use 
relative font-sizes such as em or percentages. Many simple web-pages are still 
made this way and thus scale with resolution in both KHTML and KDE WebKit.

`Allan
Received on Thursday, 14 January 2010 09:14:46 GMT

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