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Re: CSS 3 color module and deprecation of "system" colors

From: Bert Bos <bert@w3.org>
Date: Tue, 6 Sep 2005 13:32:47 +0200
To: www-style@w3.org
Message-Id: <200509061332.47649.bert@w3.org>

On Saturday 03 September 2005 16:42, Patrick H. Lauke wrote:
> Apologies for cross posting, but: could anybody shed some light as to
> why system colors have been deprecated in the CSS 3 color module?
>
> http://www.w3.org/TR/2003/CR-css3-color-20030514/#css-system
>
> In my recent testing on Windows browsers, I found them to be fairly
> well supported and would posit that they can have quite a valuable
> role to play in creating accessible style sheets that match the
> user's set colour scheme / preferences (e.g. if a user has set their
> Windows environment to High Contrast, a web page can be styled to
> follow that preference).

The reason we have system colors and the 'appearance' property is in 
fact the opposite: to allow designers to style form controls 
*differently* from the system defaults.

In the beginning, CSS said that form controls were "replaced elements," 
i.e., outside the control of the style sheet. That was a good thing for 
users, because a button always looked like a button and looked the same 
on every site. Users usually interact with many different sites, so 
this meant more efficient interaction with the Web.

But designers complained. They had designed a yellow and purple page 
with rectangular decorations and on some browsers the submit button was 
round with a pulsating blue gradient. They wanted it to be square and 
purple.

So, reluctantly, we gave in and allowed style to apply to form controls. 
But if you can say 'color: blue' on a button, then there must also be a 
way to say 'color: <not-blue>' (because color is inherited). Our first 
try was the system colors.

But system colors can't express pulsating blue gradients and for 
something that we don't expect authors to use anyway we don't want to 
create a complex system of properties that, moreover, will fail as soon 
as some OS comes with buttons of rotating polkadots...

The second try is 'appearance'. Rather than go down into the details of 
colors, shapes, shadows, etc, we went up one level. You can still make 
buttons look the way you want, but the UA style sheet can now also 
express that buttons have rotating polkadots. Simple: 'appearance: 
button'.

Accessibility doesn't play any role here. The accessibility of a site 
doesn't depend on the style chosen by the author. The Web would be 
pretty inaccessible if that were the case. Instead, CSS allows the 
author to choose whatever colors he wants and it allows the user to 
ignore them.



Bert
-- 
  Bert Bos                                ( W 3 C ) http://www.w3.org/
  http://www.w3.org/people/bos                               W3C/ERCIM
  bert@w3.org                             2004 Rt des Lucioles / BP 93
  +33 (0)4 92 38 76 92            06902 Sophia Antipolis Cedex, France
Received on Tuesday, 6 September 2005 11:32:54 GMT

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