spec selectors4

Selectors Level 4

• Selectors 3 PR
• Selectors 4 ED

Ideas considered in Editor’s Draft (ED)

• Current URL Selector (with directory levels) – :local-link()
• IDREF combinators: [/attr/](http://lists.w3.org/Archives/Public/www-style/2000Jan/0152.html) syntax, :friend(attribute, selector) syntax — /attr/ syntax chosen
• :rtl and :ltr pseudo-classes (based on source dir attributes) (or maybe :dir(rtl|ltr)?) – :dir() chosen
• ability to choose subject in the selector (alternative syntax) (discussion of syntaxes) – $ marker
• [:nth-match(<selector>, <an+b>)](http://lists.w3.org/Archives/Public/www-style/2009Mar/0146.html)
• [:matches()](http://lists.w3.org/Archives/Public/www-style/2003Apr/0146.html) pseudo-class (alternate) – :matches()
• case sensitivity in substring attribute selectors – [attr=val i] notation

Ideas to consider

• CSS4-UI more selectors (a potentially growing set of User Interface related selectors).
• pseudo-attribute selectors, e.g. to select cells that are in the second column of a table: [#column=2] – this example done with :nth-column(2)
• numeric attribute selectors, e.g. [height>2], [count<=5], [balance<0], [#row>1]
• ::quote-start and ::quote-end, to match characters with the Quotation_Mark property that are direct children of the element and that are immediately inside the start and end (respectively) of the element, ignoring White_Space characters. (This would help a lot with <q> in HTML5.)
• [:placeholder](https://developer.mozilla.org/en/CSS/%3a-moz-placeholder) - matches form elements displaying placeholder text. This allows web developers and theme designers to customize the appearance of placeholder text, which is a light grey color by default. This may not work well if you've changed the background color of your form fields to be a similar color, for example, so you can use this pseudo-class to change the placeholder text color.
• [::window](http://lists.w3.org/Archives/Public/www-style/2008Nov/0466.html) pseudo-element
• limited descendant combinator (more info) – foo>bar, foo>:not(bar)>bar, … comes hardly close
• Better definition of ::first-letter, see also note in Selectors L3
• ::first-words(n), ::first-lines(n), ::nth-line(an+b), ::last-line etc.
• semantic pseudo-class selectors e.g. for headings or "visible" elements (i.e. not <script> or <style>) akin to :link etc.
• Clarify that first formatted line is not triggered when preceded by a block http://wiki.csswg.org/spec/css2.1#issue-268
• UA hint pseudo-element selectors ::typo, ::match etc.
• empty input selector
• more of the user action pseudo-classes

Ideas superseded by other features

• relationship selectors, e.g.:
  • to select cells in a column: col.foo // td – done with td:column(col.foo)
  • to select labels applying to an input control: input // label – done without further knowledge of markup language, i.e. $label /for/ input, $label input
  • to select map elements associated with an image: img // map – opposite of input–label situation, img /usemap/ map
  • to select arbitrary associated elements: x[href#] // y[id#] – always any ID in target, x /href/ y
• only-child-parent Most use cases for the parent selector care only about the only child. This doesn't have the same perf implications as a general parent selector. – solved with :matches() and $
• dynamic values selector - already handled by ::value pseudo-element in CSS3-UI.