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[CSS21] WD 7.3: media types vs. media groups

From: Peter Moulder <peter.moulder@monash.edu>
Date: Sat, 08 Jan 2011 00:08:28 +0000
To: www-style@w3.org
Message-id: <20110108000828.GO21438@bowman.infotech.monash.edu.au>
'all':

  Is 'all' a media type or a media group?  It is currently listed as 
  both.  Note that "media types are mutually exclusive in the sense that
  a user agent can only support one media type when rendering a
  document".
    
  If 'all' really is both a media type and a media group, then does
  ‘@media all { ... }’ apply just to the 'all' media type, or to all 
  media types?
    
  I suggest that 'all' should be only a media group, not a media type.  
  In which case, I suggest removing it from the first list.
    

'speech':

  'speech' appears to be both the name of a medium and of a media group.

  Presumably, ‘speech’ in an @import or @media rule should be treated as 
  a media group rather than media type.

  This may come as a surprise to an author attempting to have an @import
  or @media rule specific to speech as distinct from tv.  It would be
  good for the spec to draw attention to this (both for implementors and
  authors). 

  aural.html depicts the speech media type as still in development.
  Is it too late to change to different names?


What media groups are exclusive of what other media groups ?

  The section on media groups is unclear as to to what extent media 
  groups are guaranteed to be mutually exclusive.  It would be helpful
  for authors to know whether or not it's possible for both 'continuous'
  and 'paged' to be matched in a given canvas, in which case they know to
  be careful about the order of ‘@media continuous’ and ‘@media paged’
  rules, or grid vs bitmap or whatever.

  The closest the spec comes at the moment is to say that "The 'tv' media 
  type, for example, is a multimodal media type that renders both
  visually and aurally to a single canvas", which strongly suggests that
  both 'visual' and 'audio' can match on a single canvas, but doesn't
  give any help as to whether or not both 'grid' and 'bitmap' could apply
  on a single canvas (perhaps for the case of a UA like w3m that usually
  restricts itself to the character grid but occasionally uses bitmap
  capabilities).  (For 'paged' and 'continuous', maybe a screen-based UA
  that uses page breaks where it judges that they enhance reading.  Even
  if you think this not a reasonable case for applying both, it's hard
  for an author to be certain that there are no cases where both would be
  applied.)


pjrm.
Received on Saturday, 8 January 2011 00:08:57 GMT

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