W3C home > Mailing lists > Public > www-style@w3.org > March 2012

Re: [selectors4] :empty psuedo class and input fields

From: L. David Baron <dbaron@dbaron.org>
Date: Tue, 13 Mar 2012 08:35:01 -0500
To: www-style@w3.org
Message-ID: <20120313133501.GA8863@pickering.dbaron.org>
On Tuesday 2012-03-13 07:18 +0800, Kang-Hao (Kenny) Lu wrote:
> (12/03/13 2:42), Christoph Päper wrote:
> > Stefan Wallin:
> >>
> >> My issue. I think the :empty pseudo class selector is not super 
> >> intuitive when it comes to form elements such as input fields.
> > 
> > Your issue, actually, is not with the ‘:empty’ pseudo-class. You 
> > want a dynamic selector for the value (attribute). David Baron 
> > suggested a pseudo-attribute, ‘[:value]’, for this
> > <http://lists.whatwg.org/pipermail/whatwg-whatwg.org/2008-October/016544.html>. 

In full, what I wrote was:

  # It seems like this belongs on the selector side of CSS, not the
  # property side.  It's not clear to me why you chose to duplicate only
  # the background-* properties, but no others.
  # 
  # I think something more like the following would work better:
  #   input[:value=""] { background: url(bang.gif) no-repeat center; }
  # perhaps with a default of:
  #   input[:value=""] { contents: attr(placeholder); }
  # 
  # (The value attribute doesn't dynamically reflect the value of the
  # input.  However, it seems reasonable to want to style based on the
  # current value; we already have the :checked pseudo-class for that
  # for some form controls.)

> > The CSS WG wiki <http://wiki.csswg.org/spec/selectors4> currently lists 
> > the ‘::value’ pseudo-element from the UI module 
> > <http://dev.w3.org/csswg/css3-ui/#pseudo-value> as an alternative, but
> > that’s wrong I think, because you cannot do attribute value comparison 
> > (‘=’, ‘^=’, ‘$=’, ‘*=’ …) with that.
> 
> The wiki has
> 
> [[
> dynamic values selector -
> already handled by ::value pseudo-element in CSS3-UI.
> ]]
> 
> . I am not quite sure what it means. '::value:empty' maybe? Would
> 'input::value:empty' be too long to be useful? I'll note that selectors4
> has this paragraph:
> 
>   # Syntactically, a pseudo-element may be followed by any combination
>   # of the user action pseudo-classes. Whether these pseudo-classes can
>   # match on the pseudo-element depends on the pseudo-class and
>   # pseudo-element's definition: unless otherwise-specified, none of
>   # these pseudo-classes will match on the pseudo-element.
> 
> so I guess we might be able to say :empty applies to ::value. Maybe.

I don't see how the ::value pseudo-element solves any of the same
problems that a :value pseudo-attribute would solve.  They're
different concepts; the pseudo-element allows styling the value and
the pseudo-attribute allows selecting on it.

-David

-- 
𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla                           http://www.mozilla.org/   𝄂
Received on Tuesday, 13 March 2012 13:35:39 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Tuesday, 22 May 2012 03:48:51 GMT