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Dimension attributes and video

From: Boris Zbarsky <bzbarsky@MIT.EDU>
Date: Wed, 25 Feb 2009 13:47:14 -0500
Message-ID: <49A59232.8090300@mit.edu>
To: HTML WG <public-html@w3.org>, whatwg <whatwg@whatwg.org>
I was just trying to figure out what the width and height attributes are 
supposed to do on <video>.  Section 4.8.7 of the spec lists these 
attributes as being possible content attributes, but that list doesn't 
link to definitions of the attributes.  The only mention I can find of 
what they do is the line:

   The video element supports dimension attributes.

which is sort of hidden in a big jumble of text.  This would all be more 
readable if there were a section for each attribute involved (or a 
single section for width+height if that makes more sense) that somehow 
set off the attribute name and then what it does.  This applies to the 
spec in general, not just to <video>.  Ideally, the list of attributes 
in the tag description would link to these sections.  The DOM specs do a 
pretty good job of a setup like this.

Past that, the "dimension attributes" section (4.8.17) doesn't tell me, 
as a UA implementor, much about what they do.  It's not even clear 
whether the inequalities given are authoring requirements or 
implementation ones (though I assume the former).  It's not clear why 
those requirements are there at all: why shouldn't one stretch "the 
image" [sic] using these attributes?  That's commonly done for <img>!

Also, why should the attributes be omitted "if the resource in question 
does not have both an intrinsic width and an intrinsic height"?

But worst of all, the only mention of what a UA is to do with these 
attributes is "give the dimensions of the visual content of the element 
(the width and height respectively, relative to the nominal direction of 
the output medium), in CSS pixels."  That doesn't tell me much.

I would think, that in a UA that supports CSS the attributes should be 
treated as presentational hints that specify the width and height CSS 
properties, right?  That's certainly how it works for <img> at the 
moment, as I recall.

-Boris
Received on Wednesday, 25 February 2009 18:48:00 UTC

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