[whatwg] CSS2 system colors in legacy color values

Ian Hickson ian at hixie.ch
Tue Aug 3 17:55:40 PDT 2010

On Sat, 22 May 2010, L. David Baron wrote:
> The "rules for parsing a legacy color value" in 
> http://www.whatwg.org/specs/web-apps/current-work/complete/common-microsyntaxes.html#rules-for-parsing-a-legacy-color-value 
> specify that CSS2 system colors should be accepted, and that they should 
> be converted to a simple color.
> It seems like a substantial amount of work to get dynamic change 
> handling correct for this case, since system colors can change 
> dynamically when the user changes system appearance.  I'd really like to 
> avoid having to add dynamic change handling for this, and I'd also like 
> to avoid having to make system colors dynamic in CSS but static in HTML.
> What was the motivation for adding support for CSS2 system colors (which 
> I would note are deprecated in css3-color) to legacy HTML color values?

On Sun, 23 May 2010, Simon Pieters wrote:
> IE compat.

On Sat, 22 May 2010, L. David Baron wrote:
> What implementations support them...

On Sun, 23 May 2010, Simon Pieters wrote:
> I think WebKit and IE.

On Sat, 22 May 2010, L. David Baron wrote:
> and do they respond to dynamic changes properly?

WebKit on Mac responds to changes to the color "Highlight" by changing the 
colour to the default blue the next time it resolves style (as far as I 
can tell). Not exactly a success story. (Highlight is the only colour over 
which the user seems to have control on Mac.)

IE8 on Windows XP apparently updates automatically (thanks to wirepair on 
#whatwg for testing that).

On Sun, 23 May 2010, Simon Pieters wrote:
> It appears that Opera and Gecko don't support system colors. I wouldn't 
> mind not supporting them, but it could be interesting to research how 
> many pages it affects.

I don't have such research, unfortunately.

I've removed the support for it for now.

On Mon, 31 May 2010, Roger Hågensen wrote:
> I'm kinda surprised that there is no support for floating point colors though.
> Althought I guess that "rgb(x%, x%, x%) An RGB percentage value (e.g.
> rgb(100%,0%,0%))"
> is as close as you get to that... Does percentage rgb color support things
> like 85.41% though?
> I hope so as only rgb(x%, x%, x%) is tentatively gamut independent.

The legacy color values are just that, legacy, the less we support there 
the better.

Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'

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