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Re: [css3-conditional] What does @supports return when the OS prevents the support?

From: L. David Baron <dbaron@dbaron.org>
Date: Thu, 7 Feb 2013 13:59:48 -0800
To: Sylvain Galineau <sylvaing@microsoft.com>
Cc: James Nurthen <james.nurthen@oracle.com>, CSS WG <www-style@w3.org>
Message-ID: <20130207215948.GB12827@crum.dbaron.org>
On Friday 2013-01-11 12:19 -0800, L. David Baron wrote:
> On Thursday 2013-01-10 19:38 +0000, Sylvain Galineau wrote:
> > 
> > [James Nurthen:]
> > > 
> > > When the CSS processor "supports" a value BUT the OS prevents the support
> > > from actually occurring what would be the result?
> > > For example. Would
> > > @supports (background-color: #CCC) return true or false when running in
> > > Windows High Contrast mode where background colours are not applied.
> > > 
> > > It would be very useful if this would return false - so this situation
> > > could be detected in CSS and appropriate styles applied.
> > > 
> > What would you expect when the document is being printed and the color might 
> > either end up in a shade of grey or the UA might disable backgrounds entirely 
> > when printing based on a user setting? 
> > 
> > Whether the UA supports a particular property-value pair and what the target 
> > media does with this same feature are orthogonal in my mind.
> I tend to agree with Sylvain here.  I think that there are other
> parts of CSS (in particular, the cascade) that are designed for the
> interaction of author and user requirements.  There also may be
> substantive cases where the user would like to override the author
> without the author knowing about it.  I'm inclined to leave
> @supports limited to describing the capabilities of the
> implementation rather than the user's configuration of it.
> (I'm distinguishing user configuration that's intended for end users
> from configuration that allows developers to try out experimental
> features and thus change the capabilities of the implementation.)

To follow up on this, the working group agreed with the conclusion
that user preferences (in the browser or system) shouldn't affect
@supports, and that @supports should also remain equivalent to what
happens with declaration fallback.

See the IRC log at
http://logs.csswg.org/irc.w3.org/css/?date=2013-02-06 (to be turned
into minutes sometime later) for the record of this discussion.


𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla                           http://www.mozilla.org/   𝄂
Received on Thursday, 7 February 2013 22:00:19 UTC

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