- From: Gregory J. Rosmaita <oedipus@hicom.net>
- Date: Tue, 18 Dec 2007 03:25:38 +0000
- To: wai-xtech@w3.org
[Reviewer's Note: this post refers to the Candidate Recommendation draft of CSS 2.1, http://www.w3.org/TR/2007/CR-CSS21-20070719 comments upon which are due by 20 December 2007] In the CSS2.1 section on media types, it explicitly states: <q src="http://www.w3.org/TR/CSS21/media.html#media-types"> Media types are mutually exclusive in the sense that a user agent can only support one media type when rendering a document. However, user agents may use different media types on different canvases. For example, a document may (simultaneously) be shown in 'screen' mode on one canvas and 'print' mode on another canvas. Note that a multimodal media type is still only one media type. The 'tv' media type, for example, is a multimodal media type that renders both visually and aurally to a single canvas. </q> Which undermines the argument that the @media all rule applies when no specific media type is specified; however, it has been made plain -- at least in email form -- from the editors of the CSS 2.1 draft -- that the @media all rule DOES apply when no specific media type is specified; consult: <http://lists.w3.org/Archives/Member/wai-liaison/2007May/0023.html> as Al Gilman, WAI PF's chair, pointed out during this exchange, in the Visual Formatting Model section, the display property is explicitly defined as pertaining to all media types, and yet, in the definition of the none value for the display property is found the following: <q cite="http://www.w3.org/TR/CSS21/visuren.html#display-prop"> none This value causes an element to generate no boxes in the formatting structure (i.e., the element has no effect on layout). Descendant elements do not generate any boxes either; this behavior cannot be overridden by setting the 'display' property on the descendants. Please note that a display of 'none' does not create an invisible box; it creates no box at all. CSS includes mechanisms that enable an element to generate boxes in the formatting structure that affect formatting but are not visible themselves. Please consult the section on visibility for details. </q> Which can be read as: "when the display property's value is none, it is not included in the formatting structure (that is, layout), but should still be available as a kind of generated content, which occupies no part of the visual canvas, but which is rendered in the aural canvas." Other than in the definition of the display property, this reviewer couldn't find another instance in the draft that indicates that it applies to all media types. It is, therefore, the Protocols & Formats working group's request that such verbiage be explicitly added to the CSS2.1 Technical Recommendation wherever and whenever appropriate, so as to remove any ambiguity as to the default media type when no media type is defined.
Received on Tuesday, 18 December 2007 03:25:45 UTC