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

From: Patrick Dengler <patd@microsoft.com>
Date: Fri, 16 Jul 2010 14:56:46 +0000
To: David Singer <singer@apple.com>, Chris Lilley <chris@w3.org>
CC: Sylvain Galineau <sylvaing@microsoft.com>, Boris Zbarsky <bzbarsky@MIT.EDU>, "www-style@w3.org list" <www-style@w3.org>, "public-fx@w3.org" <public-fx@w3.org>
Message-ID: <4A2DB3AE4504E944AF122BBFBA7FBA1F514CA2EB@TK5EX14MBXC114.redmond.corp.microsoft.com>
Let's see if I can add to this:

>>>
I'm wondering when it "doesn't make sense" to give units for a length value..  Even the zero case makes sense (I think 0cm is well-defined)!  Why isn't the suggestion "give units all the time, you know it makes sense and avoids the possibility that the author assumes X and the UA assumes Y" [1].
<<<

SVG lives entirely in a coordinate space, and is different from HTML architecturally in that manner.  Once an unit type is resolved on some top level container, then those units are interpretted into the SVG.  Coordinate systems just don't have unit types; I think that is why it doesn't make sense.  


________________________________________
From: public-fx-request@w3.org [public-fx-request@w3.org] on behalf of David Singer [singer@apple.com]
Sent: Wednesday, July 07, 2010 10:59 AM
To: Chris Lilley
Cc: Sylvain Galineau; Boris Zbarsky; www-style@w3.org list; public-fx@w3.org
Subject: Re: [css21][css3][svg] SVG and unit-less length values

OK, I'll bite...

On Jul 7, 2010, at 8:18 , Chris Lilley wrote:
>
> If they are more used to SVG (or some other vector format) and they are starting to apply that to HTML/CSS then they are surprised to find they need to add units 'even if it doesn't make sense'.
>

I'm wondering when it "doesn't make sense" to give units for a length value..  Even the zero case makes sense (I think 0cm is well-defined)!  Why isn't the suggestion "give units all the time, you know it makes sense and avoids the possibility that the author assumes X and the UA assumes Y" [1].

[1] http://www.cnn.com/TECH/space/9909/30/mars.metric/

David Singer
Multimedia and Software Standards, Apple Inc.
Received on Friday, 16 July 2010 15:09:34 GMT

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