Proposed 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.

Expectation

None of the target elements are focusable, nor do they have descendants in the flat tree that are focusable.

Assumptions

Interacting with the page does not result in changing the aria-hidden attribute value of target elements. An example of such a situation would be when closing a modal dialog makes previously hidden and not focusable elements become focusable.

Accessibility Support

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

Background

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

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.

The 1 second time span introduced in the exception of the definition of focusable is an arbitrary limit which is not included in WCAG. Given that scripts can manage the focus state of elements, testing the focused state of an element consistently would be impractical without a time limit.

Related rules

• Element with presentational children has no focusable content

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

Open in a new tab

This p element is not focusable.

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

Passed Example 2

Open in a new tab

This a element is not focusable because it is hidden through CSS.

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

Passed Example 3

Open in a new tab

This input element is not focusable because of the disabled attribute.

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

Passed Example 4

Open in a new tab

This a element is not focusable because it moves focus to the input element whenever it receives focus.

<div aria-hidden="true">
	<a href="/" style="position:absolute; top:-999em" onfocus="document.querySelector('input').focus()">First link</a>
</div>
<input />

Failed

Failed Example 1

Open in a new tab

This a element positioned off screen is focusable using the keyboard.

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

Failed Example 2

Open in a new tab

This input element is focusable because it was incorrectly disabled.

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

Failed Example 3

Open in a new tab

This button element is focusable and a descendant of an element with an aria-hidden attribute value of true because 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

Open in a new tab

This p element is focusable because of the tabindex attribute.

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

Failed Example 5

Open in a new tab

This button element is focusable because of the tabindex attribute.

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

Failed Example 6

Open in a new tab

This summary element is focusable.

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

Inapplicable

Inapplicable Example 1

Open in a new tab

This aria-hidden attribute is ignored with null value.

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

Inapplicable Example 2

Open in a new tab

This aria-hidden attribute is ignored with value false.

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

Inapplicable Example 3

Open in a new tab

This aria-hidden attribute has an incorrect value.

<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

An element is focusable if one or both of the following are true:

• the element is part of sequential focus navigation; or
• the element has a tabindex value that is not null.

Exception: Elements that lose focus during a period of up to 1 second after gaining focus, without the user interacting with the page the element is on, are not considered focusable.

Notes:

• The 1 second time span is an arbitrary limit which is not included in WCAG. Given that scripts can manage the focus state of elements, testing the focusability of an element consistently would be impractical without a time limit.
• The tabindex value of an element is the value of the tabindex attribute parsed using the rules for parsing integers. For the tabindex value to be different from null, it needs to be parsed without errors.

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.