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Re: [css3-values] Physical length units

From: Linss, Peter <peter.linss@hp.com>
Date: Thu, 23 Feb 2012 00:54:50 +0000
To: "www-style@w3.org list" <www-style@w3.org>
Message-ID: <A6FE5EF7-1BF5-46C6-A639-C424D3C91109@hp.com>
On Feb 22, 2012, at 4:12 AM, Matthew Wilcox wrote:

> Regardless, this is off topic.

Frankly, it's time to close this entire thread. There is no new information here and it's a waste of bandwidth to rehash old arguments for a matter that's been settled a long time back and the WG is not going to re-open now. We have bigger fish to fry.


Furthermore, it seems like a large part of the people involved in this conversation don't really understand the problem, or the solution.

Bottom line:

1) CSS px units are now defined as 96px per 1in. That's not going to change. Neither is the ratio between 'in' and 'cm'.

2) CSS has physical length units, and always has. They're called 'in', 'cm', 'pt' and the like. If they don't get rendered at all times at 1in = 1 inch, that's a UA issue and outside the scope of CSS. Some UAs in some circumstances should get this "right", and generally do when really they should, like print. On screens there's no guarantee, and likely never will be. Get over it. There's quite often no good way for the UA to know the exact physical properties of the screen that's being used to view the content. There's also no way to know how far away from the screen the user is and if attempting to respect physical units is even a good idea. Also, people do things like zoom, deal with it. If your web page breaks because of zoom, you're doing it wrong. Furthermore, zooming the viewport is outside the scope of CSS. If you have issues with the way UAs zoom their viewport, take it up with them. IMO, it would be nice if UAs had an option under the 'View' menu called 'Actual Size' that did the right thing.

3) Adding more units like 'true-in' is not going to happen. And if it did, they wouldn't get you what you want for all the same reasons that 'in' doesn't already always render as 1 inch. Nothing we can do about it.

4) Using physical units to specify the size of UI elements on a screen is flat out bad practice (see above about zooming). If that's what you want "true" physical units for, you're doing it wrong. Yes, there's a use case for alternative ways to solve that problem (like the proposals for a unit based on a known good control size per device), feel free to start a new thread with specific proposals for that. Frankly, it makes much more sense to size your controls in 'em's as there's generally a good relationship between the size of text that's comfortable to read and the size of a control it's comfortable to interact with (it also helps your control labels fit the control better).


Peter

CSS WG Co-Chair
Received on Thursday, 23 February 2012 00:57:47 GMT

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