Element marked as decorative is not exposed

  • Rule Type:atomic
  • Rule Id: 46ca7f
  • Last modified: Jul 14, 2020
  • Accessibility Requirements Mapping:
    • This rule is not required for conformance.

Description

This rule checks that elements marked as decorative either are not included in the accessibility tree, or have a presentational role.

Applicability

The rule applies to any element which is marked as decorative.

Expectation

Each target element either is not included in the accessibility tree or has a semantic role of none or presentation.

Assumptions

There are currently no assumptions

Accessibility Support

Implementation of the Presentational Roles Conflict Resolution differs slightly from one user agent to the other. Hence, some elements might be exposed by one user agent and not by another, and consequently might create accessibility issues only for some users. Nevertheless, triggering the conflict is a bad practice.

Background

Elements are normally marked as decorative to convey the intention of the author that they are pure decoration and thus shouldn't be exposed to assistive technologies. On the other hand, elements that are focusable are important to know for anybody and should be exposed to assistive technologies; and elements that are defining any global ARIA attribute indicate an intention to communicate something to the assistive technologies (through the aria-* attribute). When an element is both marked as decorative and either focusable or defining a global ARIA attribute, a conflict arises between these two intentions. The conflict is resolved by exposing the element.

Whenever such a conflict occurs, this indicates at the very least mismatching intentions. Such a conflict should be avoided.

When these conflicts arise on decorative non-text content, this is also a failure of Success Criterion 1.1.1: Non-text Content because decorative non-text content must be implemented in a way that allows assistive technologies to ignore it. When these conflicts arise on text content, or on content which is not decorative, this is not a failure of WCAG. Therefore this rule is not mapping to any specific WCAG Success Criterion, and is not an accessibility requirement for WCAG.

Test Cases

Passed

Passed Example 1

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This img element is marked as decorative through its alt attribute and is not included in the accessibility tree because of the aria-hidden attribute.

<img src="test-assets/shared/w3c-logo.png" alt="" aria-hidden="true" />

Passed Example 2

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This img element is marked as decorative through its alt attribute and is not included in the accessibility tree because it is hidden to everyone.

<img src="test-assets/shared/w3c-logo.png" alt="" hidden />

Passed Example 3

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This nav element is marked as decorative through its role attribute and has a semantic role of none.

<nav role="none">
	<a href="https://act-rules.github.io/" aria-label="ACT rules">ACT rules</a>
</nav>

Passed Example 4

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This img element is marked as decorative through its empty alt attribute and has semantic role of none.

<img src="test-assets/shared/w3c-logo.png" alt="" />

Passed Example 5

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This img element is marked as decorative through its role attribute and has a semantic role of none because own attributes are not required to be exposed and thus do no trigger the presentational roles conflict resolution.

<img src="test-assets/shared/w3c-logo.png" role="none" alt="W3C logo" />

Passed Example 6

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This svg element is marked as decorative through its role attribute and has a semantic role of none.

<svg role="none">
	<circle cx="50" cy="50" r="40" fill="yellow"></circle>
</svg>

Failed

Failed Example 1

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This nav element is marked as decorative through its role attribute but has a non-empty aria-label attribute causing it to be included in the accessibility tree with its implicit role of navigation.

<nav role="none" aria-label="global">
	<a href="https://act-rules.github.io/" aria-label="ACT rules">ACT rules</a>
</nav>

Failed Example 2

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This img element is marked as decorative through its empty alt attribute but has a non-empty aria-labelledby attribute causing it to be included in the accessibility tree with its implicit role of img.

<img src="test-assets/shared/w3c-logo.png" alt="" aria-labelledby="label" /> <span hidden id="label">W3C logo</span>

Failed Example 3

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This svg element is marked as decorative through its role attribute but has a non-empty aria-label attribute causing it to be included in the accessibility tree with its implicit role of graphics-document.

<svg role="none" aria-label="Yellow circle">
	<circle cx="50" cy="50" r="40" fill="yellow"></circle>
</svg>

Inapplicable

Inapplicable Example 1

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This img element is not marked as decorative.

<img src="test-assets/shared/w3c-logo.png" aria-label="W3C logo" />

Glossary

Implicit Semantic Role

The implicit semantic role of an element is a pre-defined value given by the host language which depends on the element and its ancestors.

Implicit roles for HTML and SVG, are documented in the HTML accessibility API mappings (working draft) and the SVG accessibility API mappings (working draft).

Accessibility Support for Implicit Semantic Role

  • Images with an empty alt attribute should have an implicit role of presentation, according to the HTML Accessibility API Mapping (work in progress). However, there are several popular browsers that do not treat images with empty alt attribute as having a role of presentation. Instead, they add the img element to the accessibility tree with a role of either img or graphic.

Included in the accessibility tree

Elements included in the accessibility tree of platform specific accessibility APIs. Elements in the accessibility tree are exposed to assistive technologies, allowing users to interact with the elements in a way that meet the requirements of the individual user.

The general rules for when elements are included in the accessibility tree are defined in the core accessibility API mappings. For native markup languages, such as HTML and SVG, additional rules for when elements are included in the accessibility tree can be found in the HTML accessibility API mappings (working draft) and the SVG accessibility API mappings (working draft).

Note: Users of assistive technologies might still be able to interact with elements that are not included in the accessibility tree. An example of this is a focusable element with an aria-hidden attribute with a value of true. Such an element could still be interacted with using sequential keyboard navigation regardless of the assistive technologies used, even though the element would not be included in the accessibility tree.

Examples for Included in the accessibility tree

Note: The examples presented here are non-normative and not testable. They serve to illustrate some common pitfalls about the definition and to help implementers of ACT rules understand it.

This span element is included in the accessibility tree (by default, elements are included in the accessibility tree).

<span>ACT rules</span>

This span element is not included in the accessibility tree because it is hidden to everybody by the CSS property.

<span style="display:none">ACT rules</span>

This span element is not included in the accessibility tree because it is explicitly removed by the aria-hidden attribute.

<span aria-hidden="true">ACT rules</span>

This span element is positioned off screen, hence is not visible, but is nonetheless included in the accessibility tree.

<span style="position: absolute; top:-9999em">ACT rules</span>

Although the span element with an id of "label" is not itself included in the accessibility tree, it still provides an accessible name to the other span, via the aria-labelledby attribute. Thus, it is still indirectly exposed to users of assistive technologies. Removing an element from the accessibility tree is not enough to remove all accessibility concerns from it since it can still be indirectly exposed.

<span id="label" style="display:none">ACT rules</span>
<span aria-labelledby="label">Accessibility Conformance Testing rules</span>

Although this input element is not included in the accessibility tree, it is still focusable, hence users of assistive technologies can still interact with it by sequential keyboard navigation. This may result in confusing situations for such users (and is in direct violation of the fourth rule of ARIA (working draft)).

<input type="text" aria-hidden="true" name="fname" />

Marked as decorative

An element is marked as decorative if one of the following conditions is true:

  • it has an explicit role of none or presentation; or
  • it is an img element with an alt attribute whose value is the empty string (alt=""), and with no explicit role.

Elements are marked as decorative as a way to convey the intention of the author that they are pure decoration. It is different from the element actually being pure decoration as authors may make mistakes. It is different from the element being effectively ignored by assistive technologies as rules such as presentational roles conflict resolution may overwrite this intention.

Elements can also be ignored by assistive technologies if their hidden state is true. This is different from marking the element as decorative and does not convey the same intention. Notably, the hidden state of an element may change as users interact with the page (showing and hiding elements) while being marked as decorative should stay the same through all states of the page.

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.

Semantic Role

The semantic role of an element is determined by the first of these cases that applies:

  1. Conflict If the element is marked as decorative, but the element is included in the accessibility tree; or would be included in the accessibility tree when its hidden state is false, then its semantic role is its implicit role.
  2. Explicit If the element has an explicit role, then its semantic role is its explicit role.
  3. Implicit The semantic role of the element is its implicit role.

Accessibility Support for Definition of Semantic Role for Semantic Role

  • There exist popular web browsers and assistive technologies which do not correctly implement Presentational Roles Conflict Resolution. These technologies will not include in the accessibility tree elements that should be, according to Specifications. Thus, some elements that should have their semantic role fixed by case Conflict above are instead falling into case Explicit and are hidden for users of assistive technologies.
  • A similar conflict exists for focusable elements with a aria-hidden="true" attribute. The WAI ARIA specification does not explain how to solve it. Some browsers give precedence to the element being focusable (and expose it in the accessibility tree) while some give precedence to the aria-hidden attribute (and hide the element).

Useful Links


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. This section will not be included in the rule when it is published on the W3C website.

ToolConsitencyCompleteReport
QualWebconsistentYesView Report

Acknowledgments

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