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Re: F24 - contrast

From: Ramón Corominas <rcorominas@technosite.es>
Date: Wed, 11 Dec 2013 19:39:39 +0100
Message-ID: <52A8B16B.8020806@technosite.es>
CC: 'WCAG' <w3c-wai-gl@w3.org>
Hi, David and all,

Windows high contrast mode changes any foreground colour to the selected 
"automatic" text and any background colour to the selected automatic 
background colour (remember that Windows has different high contrast 
modes, not all of them use dark backgrounds).

In any case, links are not changed to the automatic foreground colour, 
but to the default link text, which sometimes can provoke difficulties. 
Nevertheless, most users of high contrast that I know also change this 
link colour to meet their needs, either in the operating system or in 
the browser itself (browsers usually have an option to override system 

However, in technologies different from HTML, colours are not managed 
the same, and for example Word 2010 changes foreground colours to 
"automatic", but leave background colours as defined by the author, 
which in many cases provoke "white over light gray"; in addition, I 
think Adobe Reader does not change any colour unless the reflow option 
is used.

So, if the Failure only applies to HTML, then it should probably be 
removed, but if it applies to any technology, it is still valid.


David wrote:

 > The history of this is to enable users to *switch* colours (black to
 > white and vice versa) without the hard coded colours preventing then
 > change... so it black switches to white in the background but the
 > foreground doesn’t switch then you have black text on black
 > background... this is one of those success criteria that we will want to
 > look closely at, because as far as I can tell AT that switches colours
 > such as zoomtext will override even hard coded colours and successfully
 > make the change, We would have to check Windows high contrast mode, but
 > I think it does the same thing... so I question whether we should
 > continue to fail it...
 >> is F24 - http://www.w3.org/TR/2013/NOTE-WCAG20-TECHS-20130905/F24
 >> a failure even if the actual contrast meets the minimum contrast
 >> requirement ratio? In other words, if an author were to specify black
 >> text color in css (and left the default background-color of say white)
 >> where the ratio meets the success criterion de facto, would this still
 >> fail since no bgcolor was specified in the css (because the user could
 >> run into problems if he did choose a different default background color
 >> in his browser settings)?
Received on Wednesday, 11 December 2013 18:40:13 UTC

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