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Re: [CSS21] 4.3.2 Lengths (reference pixel?)

From: Felix Miata <mrmazda@earthlink.net>
Date: Fri, 10 Dec 2010 07:16:57 -0500
Message-ID: <4D021A39.7070400@earthlink.net>
To: www-style@w3.org
On 2010/12/10 10:58 (GMT+0100) Dr. Olaf Hoffmann composed:

> Boris Zbarsky composed:

>>The CSS spec doesn't say that its "mm" or "cm" units are the same as
>>actual physical mm and cm, if you will note.

> It defines:
> "
> in: inches  1in is equal to 2.54cm
> cm: centimeters
> mm: millimeters
> "
> This is quite simple to understand and to test with good accuracy in our
> time.

> If the CSS-WG thinks, that they do not need centimeters and millimeters
> or that they need unit identifiers that express something different, they
> should use other names for it to avoid confusion.
> But it is maybe a little bit late to skip absolute units like cm and mm
> in CSS2.1. They still exist in CSS2.0 and as far as I understand this,
> CSS unfortunately has no version indication. Any inconsistent change
> of a feature means for authors simply not to use it anymore, because
> it is defined in different ways in different versions of CSS.

>>Yes, this is somewhat odd.  But that's the way CSS is used in the real
>>world, it turns out.

> If the current draft is odd, I think it is time to change, to aviod, that
> finally the complete CSS gets odd ;o)

>>I suggest reading the extensive discussion on this
>>issue that's already happened.
>
> My observation about this at least with the discussion within the
> public-fx list is, that several people seem to have problems to understand
> what standards are for and what a unit like cm or mm really means ;o)
> Well, it is not a trivial thing indeed, it is physics, logic and international
> standards, not just arbitrary styling, but if there is a need for it in CSS,
> one has to care about it somehow in a qualified way.
> The current draft and the comments indicate, that there seems
> to be some need for help and I try to help to write something
> consistent and meaningful, avoiding confusing/misleading oddness.

I completely agree with Dr. Hoffmann. The newly implemented fixed ratio 
between px and absolute units has caused most of my pages on 
http://fm.no-ip.com/Auth/Font/fonts-face-index.html and others to need to be 
rewritten. Backward compatibility on the web is no longer. I could change 
those pages to work in Gecko by rewriting to use mozmm as I have in 
http://fm.no-ip.com/Auth/Font/fonts-ptdemo.html and 
http://fm.no-ip.com/Auth/dpi-screen-window.html but AFAIK there is neither 
standard nor proprietary equivalents for Opera, IE and/or Webkit to make them 
work regardless of UA.

If you want logical units in CSS, don't hijack standard unit names as was 
done with prefixes for binary multiples. Implement lpt, lmm, lcm, etc. or 
similar instead.
-- 
"The wise are known for their understanding, and pleasant
words are persuasive." Proverbs 16:21 (New Living Translation)

  Team OS/2 ** Reg. Linux User #211409

Felix Miata  ***  http://fm.no-ip.com/
Received on Friday, 10 December 2010 12:17:23 GMT

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