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Re: case sensitivity and the OM

From: L. David Baron <dbaron@dbaron.org>
Date: Mon, 17 Dec 2012 18:06:58 -0800
To: John Daggett <jdaggett@mozilla.com>
Cc: www-style list <www-style@w3.org>
Message-ID: <20121218020658.GA19916@crum.dbaron.org>
On Monday 2012-12-17 16:37 -0800, John Daggett wrote:
> >From fantasai's comments regarding case sensitivity on WG list:
> 
> > 6. If you discuss case-sensitivity, here are my positions:
> > 
> > 	a. I am ok with ASCII-insensitivity if it is just
> > 	   about matching.
> > 
> > 	b. I object to ASCII-folding if this is used anywhere
> > 	   in the OM output as a normalization of author input.
> > 
> > 	   In other words, the author must be able to pretend,
> > 	   as long as unique idents in his mind are
> > 	   case-insensitively unique, that CSS is
> > 	   case-sensitive, and have that Just Work.

I disagree with fantasai's second objection.  I think there are many
reasons to want author input to be normalized, such as:

  (1) it reduces the memory usage and performance requirements on
  implementations; we can store an 8-bit integer for "font-family"
  instead of the string "font-family".

  (2) it reduces the risk of code that's sensitive to things it
  shouldn't be sensitive to.  For example, authors might write
  javascript that looks like:

    for (var i = 0; i < declaration.length; ++i) {
      var prop = declaration[i];
      if (prop == "font-family") {
        // do something
      } else if (prop == "font-weight") {
        // do something else
      }
    }

  Today, that code works even when the CSS contains "FONT-FAMILY:
  SANS-SERIF"; changing this would probably break existing Web
  content.

For both of these reasons, normalization of author input in the
object model should be the norm rather than the exception.

-David

-- 
𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla                           http://www.mozilla.org/   𝄂
Received on Tuesday, 18 December 2012 02:07:26 GMT

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