Proposed Test Rule: Element with aria-hidden has no focusable content

Description

This rule checks that elements with an aria-hidden attribute do not contain focusable elements.

Applicability

This rule applies to any element with an aria-hidden attribute value of true.

Note: Using aria-hidden="false" on a descendant of an element with aria-hidden="true" does not expose that element. An element with aria-hidden="true" hides itself, all its content and all its descendants from assistive technologies.

Expectation

None of the target elements are part of sequential focus navigation, nor do they have descendants in the flat tree that are part of sequential focus navigation.

Assumptions

There are currently no assumptions

Accessibility Support

Some user agents treat the value of aria-hidden attribute as case-sensitive.

Background

By adding aria-hidden="true" to an element, content authors ensure that assistive technologies will ignore the element. This can be used to hide parts of a web page that are pure decoration, such as icon fonts - that are not meant to be read by assistive technologies.

A focusable element with aria-hidden="true" is ignored as part of the reading order, but still part of the focus order, making its state of visible or hidden unclear.

Bibliography

• CSS Scoping Module Level 1 (editor’s draft)
• Understanding Success Criterion 1.3.1: Info and Relationships
• Understanding Success Criterion 4.1.2: Name, Role, Value
• aria-hidden (state)
• Fourth rule of ARIA use
• Element with presentational children has no focusable content

Accessibility Requirements Mapping

• 4.1.2 Name, Role, Value (Level A)

  • Learn more about 4.1.2 Name, Role, Value
  • Required for conformance to WCAG 2.0 and later on level A and higher.
  • Outcome mapping:
    • Any failed outcomes: success criterion is not satisfied
    • All passed outcomes: success criterion needs further testing
    • An inapplicable outcome: success criterion needs further testing
• Fourth rule of ARIA use

  • Learn more about Fourth rule of ARIA use
  • Not required for conformance to any W3C accessibility recommendation.
  • Outcome mapping:
    • Any failed outcomes: WAI-ARIA rule is not satisfied
    • All passed outcomes: WAI-ARIA rule needs further testing
    • An inapplicable outcome: WAI-ARIA rule needs further testing

Input Aspects

The following aspects are required in using this rule.

• DOM Tree
• CSS Styling

Test Cases

Passed

Passed Example 1

Content not focusable by default.

<p aria-hidden="true">Some text</p>

Passed Example 2

Content hidden through CSS.

<div aria-hidden="true">
	<a href="/" style="display:none">Link</a>
</div>

Passed Example 3

Content taken out of sequential focus order using tabindex.

<div aria-hidden="true">
	<button tabindex="-1">Some button</button>
</div>

Passed Example 4

Content made unfocusable through disabled attribute.

<input disabled aria-hidden="true" />

Passed Example 5

aria-hidden can’t be reset once set to true on an ancestor.

<div aria-hidden="true">
	<div aria-hidden="false">
		<button tabindex="-1">Some button</button>
	</div>
</div>

Failed

Failed Example 1

Focusable off screen link.

<div aria-hidden="true">
	<a href="/" style="position:absolute; top:-999em">Link</a>
</div>

Failed Example 2

Focusable form field, incorrectly disabled.

<div aria-hidden="true">
	<input aria-disabled="true" />
</div>

Failed Example 3

aria-hidden can’t be reset once set to true on an ancestor.

<div aria-hidden="true">
	<div aria-hidden="false">
		<button>Some button</button>
	</div>
</div>

Failed Example 4

Focusable content through tabindex.

<p tabindex="0" aria-hidden="true">Some text</p>

Failed Example 5

Focusable summary element.

<details aria-hidden="true">
	<summary>Some button</summary>
	<p>Some details</p>
</details>

Inapplicable

Inapplicable Example 1

Ignore aria-hidden with null value.

<button tabindex="-1" aria-hidden>Some button</button>

Inapplicable Example 2

Ignore aria-hidden false.

<p aria-hidden="false">Some text</p>

Inapplicable Example 3

Incorrect value of aria-hidden.

<div aria-hidden="yes">
	<p>Some text</p>
</div>

Glossary

Attribute value

The attribute value of a content attribute set on an HTML element is the value that the attribute gets after being parsed and computed according to specifications. It may differ from the value that is actually written in the HTML code due to trimming whitespace or non-digits characters, default values, or case-insensitivity.

Some notable case of attribute value, among others:

• For enumerated attributes, the attribute value is either the state of the attribute, or the keyword that maps to it; even for the default states. Thus <input type="image" /> has an attribute value of either Image Button (the state) or image (the keyword mapping to it), both formulations having the same meaning; similarly, “an input element with a type attribute value of Text” can be either <input type="text" />, <input /> (missing value default), or <input type="invalid" /> (invalid value default).
• For boolean attributes, the attribute value is true when the attribute is present and false otherwise. Thus <button disabled>, <button disabled="disabled"> and <button disabled=""> all have a disabled attribute value of true.
• For attributes whose value is used in a case-insensitive context, the attribute value is the lowercase version of the value written in the HTML code.
• For attributes that accept numbers, the attribute value is the result of parsing the value written in the HTML code according to the rules for parsing this kind of number.
• For attributes that accept sets of tokens, whether space separated or comma separated, the attribute value is the set of tokens obtained after parsing the set and, depending on the case, converting its items to lowercase (if the set is used in a case-insensitive context).
• For aria-* attributes, the attribute value is computed as indicated in the WAI-ARIA specification and the HTML Accessibility API Mappings.

This list is not exhaustive, and only serves as an illustration for some of the most common cases.

The attribute value of an IDL attribute is the value returned on getting it. Note that when an IDL attribute reflects a content attribute, they have the same attribute value.

Focusable

Elements that can become the target of keyboard input as described in the HTML specification of focusable and can be focused.

Outcome

An outcome is a conclusion that comes from evaluating an ACT Rule on a test subject or one of its constituent test target. An outcome can be one of the three following types:

• Inapplicable: No part of the test subject matches the applicability
• Passed: A test target meets all expectations
• Failed: A test target does not meet all expectations

Note: A rule has one passed or failed outcome for every test target. When there are no test targets the rule has one inapplicable outcome. This means that each test subject will have one or more outcomes.

Note: Implementations using the EARL10-Schema can express the outcome with the outcome property. In addition to passed, failed and inapplicable, EARL 1.0 also defined an incomplete outcome. While this cannot be the outcome of an ACT Rule when applied in its entirety, it often happens that rules are only partially evaluated. For example, when applicability was automated, but the expectations have to be evaluated manually. Such “interim” results can be expressed with the incomplete outcome.

Visible

Content perceivable through sight.

Content is considered visible if making it fully transparent would result in a difference in the pixels rendered for any part of the document that is currently within the viewport or can be brought into the viewport via scrolling.

Content is defined in WCAG.

For more details, see examples of visible.

Implementations

This section is not part of the official rule. It is populated dynamically and not accounted for in the change history or the last modified date.

Changelog

This is the first version of this ACT rule.