Issues for Level 4

• Lift restriction preventing combinators in :any/:not in the fast profile?
• Anything else that should be moved from complete to fast profile?
• Syntax of subject indicator
• Comma-separated [attr] values, for easy OR matching?
• Numeric [attr] comparators?
• Name of :any-link - maybe put “link” first in the name, like :link-any?
• Does :local-link(n) force N path segments to match, or can a document with a shorter url still create a match? (Example: in https://github.com/tabatkins/css-preprocessor, does :local-link(2) mean “same user and repository only”, or does it allow “https://github.com/tabatkins”, thus implicitly allowing “same user, but no specified repo”?)
• Naming the drag-and-drop pseudoclasses
• Just point the An+B grammar section to Syntax, now that it’s accepted?
• dbaron is uncertain about the reference and column combinators, the :matches() syntax (naming? something else?) and the subject indicator.

Brainstorming for Selectors Level 5

• Selectors 3 PR
• Selectors 4 ED

Ideas to consider

• 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 - 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 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
• More time pseudo-classes: :time([ before <time> | after <time> | <time> to <time> ])
• :only-whitespace: :empty is kinda useless, since it requires you to have *nothing* between the start and end tag. This is hostile to common markup patterns which might put the end tag on a separate line.

Ideas superseded by other features

• relationship selectors, e.g.:
  • to select cells in a column: col.foo // td
  • to select labels applying to an input control: !label /for/ input
  • to select map elements associated with an image: img /usemap/ map
  • to select arbitrary associated elements: 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.