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Does filtering count as "change of context" as regards WCAG 3.2.2

for

From: Robert Fentress
Date: Jun 16, 2017 10:46AM

A pattern you see more and more is when a user changes the setting of an
interface component in a web page, such as a select element, checkbox or
text field, and it dynamically filters the results displayed in the main
content area of the page. Does WCAG 3.2.2
<https://www.w3.org/TR/UNDERSTANDING-WCAG20/consistent-behavior-unpredictable-change.html#context-changedef>
require, then, that the user be informed that making such changes will have
this effect before he or she begins interacting with the control? That
criteria as is as follows, by the way:

*On Input:* Changing the setting of any user interface component does not
automatically cause a change of context unless the user has been advised of
the behavior before using the component.


If the user must be informed, is it sufficient to make a blanket statement
somewhere on the page before these controls that says something like
"changing the value of these controls dynamically filters the results
below." For web applications, would it be sufficient to provide
instructions in the documentation. Or must the control be semantically
associated with the in-page instructions, by doing something like adding
aria-describedby to the control and pointing to the id of the
instructions? Would doing so make things too verbose? My justification
for making that explicit association is that users may just tab to the
control and miss the instructions, otherwise.

Also, I like the idea of using a polite ARIA live region to announce the
number of results returned in a non-verbose way, like "5 results." Anybody
think that is bad practice? Just seems like that is a useful affordance
that more closely approximates the experience of sighted users. What do
you think?

Best,
Rob

--
Rob Fentress
Senior Accessibility Solutions Designer
Assistive Technologies at Virginia Tech
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