Re: Color contrast below 4.5:1 in subset of browsers and devices - WCAG pass or fail?

Ok, that makes sense, but what about these:

1) Does it mean you can document High Contrast Mode as "relied upon" to pass 2.3.1? If so, doesn’t that render the contrast checkpoints useless?

2) In the presence of CSS parsing errors, colours may turn out different between browsers, or different versions of the same browser. For example, on this CSS WG test page:
http://test.csswg.org/suites/css21_dev/20110323/html4/uri-013.htm

IE11 - all lines have a green background 
Chrome 73 - some lines have a red background, others have green background
Firefox 48 - all lines have a green background
Firefox 67 - some lines have a red background, others have green background
Safari 9 - some lines have a red background (but not the same red lines as Firefox 67)

It's seems less clear that relying on parsing quirks is a 'relied upon' technology and 4.1.1 Parsing doesn't apply here since CSS isn't a markup language. There are rules for handling errors in CSS, but these changed between CSS 2.1 and 3.0 and are less consistently implemented than the HTML error handling rules.

3)  What happens if the contrast only falls below threshold at certain screen sizes or screen orientations. For example:
@media ( max-width: 400px ) { input { color: #eee, background: #fff; }
@media ( orientation: landscape ) { input { color: #eee, background: #fff; }
That doesn’t seem to quite fit 'relied upon' definition and the orientation query also interacts with 1.3.4 Orientation.

4) What happens if an @supports rule breaks contrast in a specific browser:
@supports ( -moz-box-align ) { input { color: #eee, background: #fff; }
This passes if you can rely on something not being implemented, but it's difficult to see how the 'relied upon' wording fits this situation

5) What happens if the failure doesn't occur in older browsers because they don't support a specific technology like CSS gradients:
input { color: #eee, background-color: #000; background: linear-gradient(45deg, : #fff, : #fff); }
Can you 'rely upon' an older implementation for conformance?

I guess the problem I'm driving at is the contrast problem can occur in lots of different ways, and it's undesirable if the same problem sometimes passes and sometimes fails depending on how it's implemented, even though the impact on the user is the same.

Thanks
Mark


On 28/05/2019, 17:08, "Patrick H. Lauke" <redux@splintered.co.uk> wrote:

    This sounds like the :read-only and :read-write selectors here are 
    "relied upon" https://www.w3.org/TR/WCAG21/#dfn-relied-upon (when 
    they're not supported, contrast fails).
    
    While the normative definition of "accessibility supported" 
    https://www.w3.org/TR/WCAG21/#dfn-accessibility-supported indeed talks 
    about AT and accessibility features in browsers/UAs, I'd say at least in 
    the spirit of that definition I'd also include using/relying on web 
    technologies that have widespread browser support, unless you know for a 
    fact that end users won't actually be using Firefox or IE (e.g. if it's 
    in a closed/controlled environment).
    
    A very strict reading of WCAG would, to me, suggest this is not a hard 
    failure of 1.4.3, but in an audit (if discovered) I'd certainly at the 
    very least flag it as a very strong best practice recommendation to fix it.
    
    P
    -- 
    Patrick H. Lauke
    
    www.splintered.co.uk | https://github.com/patrickhlauke
    http://flickr.com/photos/redux/ | http://redux.deviantart.com

    twitter: @patrick_h_lauke | skype: patrick_h_lauke

Received on Wednesday, 29 May 2019 12:22:08 UTC