Re: Understanding of SC 1.4.11

Hi Jon,
I've contributed to a number of rewrites, and if you're asking questions, 
obviously I need another kick at the can. Note that in the latest version 
I gave Alastair, I'm recommending some visual examples for both boundary 
and 'adjacent colors' which may clarify your first paragraph questions.

> In one case we talk about the boundaries with the adjacent background 
and the other the adjacent background of the component.  When we measure 
contrast what is the contrast requirement? for both sides of the border or 
only for one side?  Does it matter if it’s the inside or the outside?

So the SC text talks about "visual information used to 
indicate...boundaries of user interface components". It also talks about 
"parts of graphics required to understand content". Two different things, 
which will both come into play in answering your question.

We only care about the contrast with the outside of any boundary of the UI 
component when meeting the first bullet of the SC. The issue here is that 
if there is a visual indication of the boundary, we want more users to be 
able to detect it. So if there is a visual indication, it must meet 
minimum contrast. Note that this doesn't require a boundary; if no one is 
shown the boundary of the component, then everyone is equally not shown.

For the second part of the bullet, we care about the contrast between 
parts of the graphic that convey meaning. In a situation where the graphic 
is a UI component, a few things come into play. Let's first off assume 
there is no visual boundary for the control. Where I have a monochromatic 
shape, I only care about the contrast between its edge and the adjacent 
background. Where I have a two-colour shape, I'll need to care about all 
edges of both colors, both where they meet, and where they meet the 
adjacent background color.
If there is a boundary, I'm going to care about its outside edge as per 
the first bullet of the SC. But I am also going to care about the division 
between the inside edge of the boundary and any internal graphic of the 
component IF that division contributes to the understand of the shape. In 
other words, is the boundary separated from the internal shape (by the 
background page color) or does the boundary edge meet the internal shape?


Michael Gower
IBM Accessibility
Research

1803 Douglas Street, Victoria, BC  V8T 5C3
gowerm@ca.ibm.com
cellular: (250) 661-0098 *  fax: (250) 220-8034



From:   Jonathan Avila <jon.avila@levelaccess.com>
To:     WCAG <w3c-wai-gl@w3.org>
Date:   2018-04-30 12:11 PM
Subject:        Understanding of SC 1.4.11



1.       Seeking clarity on contrast of bounds/state
 
In reading through the understanding doc on SC 1.4.11 non-text contrast I 
wanted to make sure I understand the following statement regarding the 
contrast “visual boundaries of the component must have sufficient contrast 
with the adjacent background” and also regarding the state “ adjacent 
background of the component.”
 
In one case we talk about the boundaries with the adjacent background and 
the other the adjacent background of the component.  When we measure 
contrast what is the contrast requirement? for both sides of the border or 
only for one side?  Does it matter if it’s the inside or the outside?
 
2.       Seeking clarity on reference to SC 1.4.1 Use of Color in 
understanding 1.4.11. 
 
I agree with what is written under the note SC 1.4.1.  But the references 
seem a little out of place and I think it might be worth discussing to 
make sure we are all on the same page.  The way I read the reference is 
that states used for adjacent controls such as to indicate that one toggle 
button is pressed and another is not cannot rely on difference lightness 
unless the lightness is >= 3:1.  The exception is if the state is also 
communicated with some other visual mechanism then the contrast between 
states can use any ratio of lightness.       I’ve always read 1.4.1/1.4.3 
this way but wanted to understand the reference to 1.4.1 to understand 
were one should be flagging this issue.   Should it be flagged under 1.4.1 
Color or 1.4.11 non-text contrast if no other mechanism is available other 
than contrast < 3:1 to show state?
 
Jonathan