[Bug 10606] New: Define what alt="<whitespace>" means for <img>


           Summary: Define what alt="<whitespace>" means for <img>
           Product: HTML WG
           Version: unspecified
          Platform: PC
               URL: http://dev.w3.org/html5/spec/embedded-content-1.html#i
        OS/Version: All
            Status: NEW
          Keywords: a11y
          Severity: normal
          Priority: P3
         Component: HTML5 spec (editor: Ian Hickson)
        AssignedTo: ian@hixie.ch
        ReportedBy: xn--mlform-iua@xn--mlform-iua.no
         QAContact: public-html-bugzilla@w3.org
                CC: mike@w3.org, public-html@w3.org

PROPOSAL:  augment the definition of alt="<non-empty-string> to clearly cover
ALT. 2 PROPOSAL: define alt="<whitespace>" as equal to omitted @alt.
ALT. 3 PROPOSAL: One of the two alternative above, with a warning against use
of alt="<whitespace>"
ALT. 4 PROPOSAL: A separate definition of the semantics of alt="<whitespace>"

   (1) authors might easily think of alt=<whitespace> as equlaato
alt=<empsty-string>  when it comes to the effect it has for AT users. Whereas,
in reality, e.g. VoiceOver+Safari announces the presence of any image whose
@alt contains whitespace: if the content is a single space character, then it
announcees "space, image", and if it contains two spaces, then it announces
  (2) Authors might not trust the effect of omitting the @alt - and the spec
also includes warnings against omitting @alt.
  (3) alt="<empystring>"  triggers role="presentation", whereas
role="<whitespace>" triggeres role="img". Thus authors could easily start doing
alt="<whitespace>" instead of role="img". (In VoiceOver+Webkit, it works that
way - see bug 10604.)


   AUTHOR BENEFITS OF alt="<whitespace>": The author might want to ensure that
the user is able to download the image, and whitespace does provide that
functionality. (The alternative for the author, is to use role="img", to omit
the @alt or to provide some other @alt text.)

   NEGATIVE SIDES OF alt="<whitespace>" Ambiguity: the semantics of a space
character is ambiguous. E.g. in GUI browsers, if image is unavailable, then it
will be replaced be a space, which is often not a good way to represent an
image. It is also probably difficult for authors to keep track of whether they
intentionally inserted a whitespace, or whether they meant to insert the empty

  OTHER THINGS: Difficult to interpret for the sighted user if the fallback is
the empty string. 

      about @alt with non-empty string:
]]  The image is a key part of the content; the alt attribute gives a textual
equivalent or replacement for the image. [[
      about absent/omitted @alt
]] The image might be a key part of the content, and there is no textual
equivalent of the image available. [[ 
     about @alt with the empty string:
]] The image is either decorative or supplemental to the rest of the content,
redundant with some other information in the document. [[

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Received on Sunday, 12 September 2010 03:55:44 UTC