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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 10:51:41 -0700
Cc: "Dr. Olaf Hoffmann" <Dr.O.Hoffmann@gmx.de>, public-fx@w3.org, www-style@w3.org
Message-Id: <EFC39AA4-65B7-49CD-B5A8-EA103BF6AD16@gmail.com>
To: Doug Schepers <schepers@w3.org>

On Aug 14, 2010, at 9:56 AM, Doug Schepers wrote:

> Hi, Folks-
> 
> I was under the impression that it was not possible to render real-world units to uncalibrated monitors, and that most monitors are uncalibrated; am I mistaken or confused (maybe thinking of color calibration), or has that changed?

I don't know if "calibration" is the correct word, but yes, there is the problem of the monitor/video-card combination not reporting the real-word size accurately enough to be reliable. There is also the case of projectors, and we cannot insist that everyone get new fancier projectors that can report back the screen distance to the system, in order to keep layouts from breaking. There are also video billboards and scoreboards, which if they did accurately report their physical size and that was used for the layout, would most assuredly create poor or unreadable results. On the other end of the scale, there are things like video spectacles, where the image is very tiny (thus also breaking layouts if the author has something rendered as a _true_ couple of inches) but where also the image may appear larger and farther away because the binocular effect intentionally makes it appear so. And who knows what the future will bring? Direct neural interfaces where the concept of an inch is completely fluid and thus meaningless?

Most authors will not expect their layout to change its proportions drastically based on viewing distance on the size or resolution of a device at the same distance.

> Wouldn't it be possible to meet both use-cases by adding a property, something like 'unit-space':'realteive*|absolute', where the default is to use these abstracted units (for necessary bugwards compatibility), and the 'absolute' option would do its best to render the physical size as indicated?  This would be something like dealing with transforms or viewboxes.

That seems dangerous. An author might routinely put 'unit-space:absolute' in his style sheet because he does fully understand it, and it seems reasonable and looks OK on his 280 ppi monitor. Then the page is viewed by someone else on a 72 ppi monitor, and all the 1px borders become sub-pixel widths, and all his 15px square icons look like crap, and everything renders slower. The Web is supposed to be fault tolerant, and this would seem to instead invite unintended rendering.
Received on Saturday, 14 August 2010 17:52:21 GMT

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