W3C home > Mailing lists > Public > www-svg@w3.org > February 2012

Re: path data attribute lacks units!

From: Dr. Olaf Hoffmann <Dr.O.Hoffmann@gmx.de>
Date: Mon, 13 Feb 2012 10:53:26 +0100
To: www-svg@w3.org
Message-Id: <201202131053.27017.Dr.O.Hoffmann@gmx.de>
Doug Schepers:

>Uncalibrated screens, or those running at variable resolutions, are not 
>expected to be absolute in terms of pixel size.

Well, to get an absolute size correct on screens worked already for 
example in earlier versions of Geckos/Firefox pretty good, but was 
pessimised maybe related to the units obfuscation in CSS 2.1.

>Print, on the other hand, can afford these real-world measurement units.

Of course, this is possible for screens as well, because typically the 
operating systems knows the current resolution of the screen.
At least for TFT-LCD monitors, not necessarily for CRT monitors,
it is not useful anymore to change the resolution (device pixels per mm)

According to my tests, not all typical viewers manage to generate
a printing output of 10 cm if 10 cm is noted in a file. 
The obfuscation of CSS 2.1 is simply inherited for printing as well.

>Thus, units in SVG are as useful as can be expected for screens, and as 
>useful as is necessary for print.

In theory yes, in practice not reliable without further information for the 
user, not familiar with the CSS 2.1 units problem.
For screens the situation is not as useful as can be expected, it is hopeless.
And for printing it depends strongly on the program, if this inherits the
CSS 2.1 units obfuscation to printing output as well or not.
If you want to send a scale drawing to someone, at least you have to add
an instruction, how to print it to get the intended size or how to determine
a scaling factor for the screen to get it right for specific viewers.

Therefore SVG ist much more useful for applications without absolute units 
in it.

Received on Monday, 13 February 2012 09:53:59 UTC

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