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Re: [css21][css3][svg] SVG and unit-less length values

From: Brad Kemper <brad.kemper@gmail.com>
Date: Sat, 14 Aug 2010 14:17:58 -0700
Cc: "Tab Atkins Jr." <jackalmage@gmail.com>, "Dr. Olaf Hoffmann" <Dr.O.Hoffmann@gmx.de>, public-fx@w3.org, www-style@w3.org
Message-Id: <4720886D-BFB7-4FC8-B50D-E4415EAA1ABB@gmail.com>
To: Doug Schepers <schepers@w3.org>

On Aug 14, 2010, at 12:57 PM, Doug Schepers wrote:

> Yet there are times and circumstances where that is useful, and where it's worth the effort for the user to calibrate their monitor with a real-world reference (like holding up a ruler to their screen).  For example, in architectural drawings, or with widgets that let you measure things onscreen, like calipers.  SVG is more graphical than CSS+HTML, so these sorts of things do arise more often, perhaps, in SVG.
> 
> We are trying to move SVG and CSS closer together, so we need to consider use cases from both.  That said, the most common case (outside of printing, which is too often ignored) does seem to weigh heavily in favor of the abstracted units.

I think it is reasonable for the device (or an abstraction of it in the device driver, for instance) to decide if it puts the priority on physical units or on pixels. Thus, for high resolution printers, 1px is determined by dividing 1 physical inch by 96. For most monitors, it would be the other way, and 1" is determined by multiplying 1px by 96. In theory, I don't see why a specialized UA, such as one made to display CAD files, could not opt to be more printer-like in that regard. But I don't think it should break the proportions between inches, etc. and CSS pixels (aside from rounding to whole device pixels, and/or otherwise indicating their presence by, say, making them more transparent or whatever at sub-device-pixel sizes).
Received on Saturday, 14 August 2010 21:18:36 GMT

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