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Re: Specifying foreground and background colors

From: Peter Verhoeven <pav@oce.nl>
Date: Wed, 14 Jun 2000 09:06:21 +0200
Message-Id: <4.3.1.1.20000614090325.00b2f9a0@pophost.oce.nl>
To: Charles McCathieNevile <charles@w3.org>, Wendy A Chisholm <wendy@w3.org>
Cc: w3c-wai-gl@w3.org, w3c-wai-ua@w3.org, w3c-wai-er-ig@w3.org
Hi Charles,

I fully agree with you. If one color is specified or an background image is 
used ALL colors must be set. An authoring, evaluation or repair tool can 
check on this and can also warn if a bad color contrast is set.
This should highly improve accessibility.

Regards Peter Verhoeven
Internet : http://www.magnifiers.org (The Screen Magnifiers Homepage)

At 22:06 13-06-2000 -0400, Charles McCathieNevile wrote:
>The accessibility requirement is to have sufficient contrast. With only one
>colour specified, there is no known contrast.
>
>This is not primarily a UA issue (in my opinion), but an Authoring issue. It
>is possible for a UA to repair it, of course, but it has to do so by
>guesswork (although it is likely to de a better job than a person in many
>instances. That means that when this repair strategy is automatically
>implemented in Authoring tools we may get an overall improvement - depends on
>the algorithms and interfaces...)
>
>Cheers
>
>Charles
>
>On Tue, 13 Jun 2000, Wendy A Chisholm wrote:
>
>   At 12:59 AM 6/10/00 , Charles McCathieNevile wrote:
>   >Assuming a particular colour combination is a user's default and that
>   >therefore it is only necessary to specify colours for things that are 
> not the
>   >default is a mistake.
>   >(particularly for accessiblity reasons they may choose
>   >something else, although there may be other reasons. I don't know that 
> it is
>   >a reason not to include the technique, as the way to specify thinigs
>   >correctly.)
>
>   My main question is not "should we include this as a technique."
>
>   Rather, my question is, "what is the accessibility rationale for this
>   technique."  I did not see any, thus did not include any in my proposal.
>
>   I think the rationale is "good design."  Regardless of whether I choose a
>   high-contrast background and foreground color combination (white and dark
>   red), if the user only selects a foreground color (white) current user
>   agents will not select a high contrast background color.  They will 
> display
>   the author set background color (white) and the user set foreground color
>   (white).  The user will have to select a foreground color as well.  In 
> some
>   browsers, the user could select "high-contrast mode" where the browser
>   selects both the foreground and background colors.  For example, yellow
>   text on a black background.
>
>   >Maybe we should ask the ER or UA groups to look in more detail at the 
> issue
>   >of ensuring contrast? Most User Agents allow a choice of colours, although
>   >most do not automatically pick a contrasting colour where there is a 
> conflict
>   >or semi-specified colour scheme.
>
>   I think this is a UA issue and have CC'ed the UA working group.  Chris
>   Ridpath recently published results of a color study, so I have CC'ed ER as
>   well.  Refer to the techniques for Checkpoint 2.2 in the 26 April 2000
>   working draft of AERT [1].
>
>   Since there do not appear to be any objections to my proposed edit of the
>   CSS techniques module, I will make the appropriate changes.
>
>   --wendy
>
>   [1] http://www.w3.org/TR/AERT#color-contrast
>
>
>   >On Thu, 8 Jun 2000, Wendy A Chisholm wrote:
>   >
>   >   I have two questions in relation to this issue:
>   >   1. will user agents automatically make adjustments for background or
>   >   foreground color if the author specifies a good combination but the 
> user
>   >   only specifies one or the other (foreground or background but not
>   >   both)?  It is my experience that user agents do not.
>   >
>   >   2. I intend to include this in the techniques document, but would 
> like a
>   >   rationale.  It seems that the rationale is good design rather than an
>   >   accessibility issue since the answer to the first question seems to be
>   > "no."
>   >
>   >   If there is no disagreement, I propose editing section 5 (Colors) 
> of the
>   >   CSS techniques module to read:
>   >   <blockquote>
>   >   Use these CSS properties to specify colors:
>   >   'color', for foreground text color.
>   >   'background-color', for background colors.
>   >   'border-color', 'outline-color' for border colors.
>   >   For link colors, refer to the :link, :visited, and :active 
> pseudo-classes.
>   >
>   >   Note that when a background color is specified, specify a high-contrast
>   >   foreground color and vice-versa.
>   >
>   >   Ensure that information is not conveyed through color alone. For 
> example,
>   >   when asking for input from users, do not write "Please select an 
> item from
>   >   those listed in green." Instead, ensure that information is available
>   >   through other style effects (e.g., a font effect) and through context
>   >   (e.g,. comprehensive text links).
>   >   For instance, in this document, examples are styled by default (through
>   >   style sheets) as follows:
>   >   They are surrounded by a border.
>   >   They use a different background color and also specify a high-contrast
>   >   foreground color.
>   >   They begin with the word "Example" (or "Deprecated Example".
>   >   They also end with the phrase "End example", but that phrase is 
> hidden by
>   >   default with 'display: none'. For user agents that don't support style
>   >   sheets or when style sheets are turned off, this text helps 
> delineate the
>   >   end of an example for readers who may not be able to see the border 
> around
>   >   the example.
>   >   </blockquote>
>   >   --wendy
>   >
>   >   At 12:59 AM 6/7/00 , Wendy A Chisholm wrote:
>   >   > From the issues list:
>   >   >
>   >   ><blockquote>
>   >   >Issue raised by: Philip Newton - 7 May 1999
>   >   >Issue:
>   >   >If the author specifies a background color, they should also 
> specify the
>   >   >foreground color (and vice versa), otherwise if the user has 
> selected a
>   >   >particular foreground color that does not contrast well with the 
> author's
>   >   >background color, the page will be unreadable.
>   >   >
>   >   >Proposed Resolution
>   >   >While the user should be able to adjust preferences on the user 
> agent, it
>   >   >is good design. Therefore, it seems to make sense to discuss in
>   > techniques doc.
>   >   ></blockquote>
>   >   >
>   >   >Even if the author selects both a background and text color, if 
> the user
>   >   >selects a foreground color that does not contrast well with the 
> author's
>   >   >background color then what can you do?  If the user only selects one
>   > color
>   >   >but the author has selected both foreground and background, the user
>   > agent
>   >   >will not automatically use colors that contrast well, will it?
>   >   >
>   >   >I agree this is good practice but I am not sure that this increases
>   >   >accessibility.
>   >   >
>   >   >Thoughts?  Do people have experiences that support the proposal?  Does
>   >   >someone have a good test page for this?
>   >   >--wendy
>   >   >--
>   >   >wendy a chisholm
>   >   >world wide web consortium
>   >   >web accessibility initiative
>   >   >madison, wi usa
>   >   >tel: +1 608 663 6346
>   >   >/--
>   >
>   >   --
>   >   wendy a chisholm
>   >   world wide web consortium
>   >   web accessibility initiative
>   >   madison, wi usa
>   >   tel: +1 608 663 6346
>   >   /--
>   >
>   >
>   >--
>   >Charles McCathieNevile    mailto:charles@w3.org    phone: +61 (0) 409 
> 134 136
>   >W3C Web Accessibility 
> Initiative                      http://www.w3.org/WAI
>   >Location: I-cubed, 110 Victoria Street, Carlton VIC 3053
>   >Postal: GPO Box 2476V, Melbourne 3001,  Australia
>
>   --
>   wendy a chisholm
>   world wide web consortium
>   web accessibility initiative
>   madison, wi usa
>   tel: +1 608 663 6346
>   /--
>
>
>--
>Charles McCathieNevile    mailto:charles@w3.org    phone: +61 (0) 409 134 136
>W3C Web Accessibility Initiative                      http://www.w3.org/WAI
>Location: I-cubed, 110 Victoria Street, Carlton VIC 3053
>Postal: GPO Box 2476V, Melbourne 3001,  Australia
Received on Wednesday, 14 June 2000 03:17:46 GMT

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