Support CSS specificity

[ju1ius]

The support for specificity would allow CSSParser to merge RuleSets according to CSS cascading rules (http://www.w3.org/TR/REC-CSS2/cascade.html#cascading-order).

But I think it would need a bit of redesign.
The statement
#myid .someclass, foo.bar { mydeclaration: myvalue}
should be parsed as two CSSSelector objects having the same rules but a different specificity.

I invite you to have a look to http://github.com/alexdunae/css_parser, and in particular to https://github.com/alexdunae/css_parser/blob/master/lib/css_parser.rb for the css specificity thing.

[ju1ius]

here is a working code for computing specificity. It supports everything but the negation pseudo-class:

// in class CSSParser
const
  NON_ID_ATTRIBUTES_AND_PSEUDO_CLASSES_RX = '/
    (\.[\w]+)                    # classes
    |
    \[(\w+)                      # attributes
    |
    (\:(                         # pseudo classes
      link|visited|active
      |hover|focus
      |lang
      |target
      |enabled|disabled|checked|indeterminate
      |root
      |nth-child|nth-last-child|nth-of-type|nth-last-of-type
      |first-child|last-child|first-of-type|last-of-type
      |only-child|only-of-type
      |empty|contains
    ))
  /ix',
  ELEMENTS_AND_PSEUDO_ELEMENTS_RX = '/
    ((^|[\s\+\>\~]+)[\w]+ # elements
    |                   
    \:{1,2}(                 # pseudo-elements
      after|before
      |first-letter|first-line
      |selection
    )
  )/ix';

public static function computeSpecificity($selector)
{
  $a = 0;
  $b = substr_count($selector, '#');
  $c = preg_match_all(self::NON_ID_ATTRIBUTES_AND_PSEUDO_CLASSES_RX, $selector, $matches);
  $d = preg_match_all(self::ELEMENTS_AND_PSEUDO_ELEMENTS_RX, $selector, $matches);
  return ($a*1000) + ($b*100) + ($c*10) + $d;
}

[sabberworm]

I’m closing this as I dont’t think there will ever be a merge method.