Support aria-description (#69) · w3c/accname@81361ec (original) (raw)

`@@ -200,22 +200,70 @@

Name and Description

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author

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name is generated from values provided by the author in explicit markup features such as the aria-label and aria-labelledby [=attribute=], or a host language labeling mechanism, such as the alt or title [=attribute=] in HTML, or the desc [=element=] in SVG.

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contents

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name is generated from the Text [=nodes=] associated with the [=element=]. Although this may be allowed in addition to "author" in some roles, "content" is used only if higher priority "author" features are not provided. Priority is defined by the accessible name and description computation algorithm.

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prohibited

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the element has no name. Authors MUST NOT use the aria-label or aria-labelledby attributes to name the element.

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The Accessible Rich Internet Applications (WAI-ARIA) 1.2 [[!WAI-ARIA]] specification provides lists of roles that support name from author, roles that support name from content and roles that cannot be named.

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Name Computation

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User agents MUST compute an accessible name using the rules outlined below in the section titled Accessible Name and Description Computation.

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User agents MUST compute an accessible name using the rules outlined below in the section titled Text Equivalent Computation.

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Description Computation

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If aria-describedby is present, user agents MUST compute the accessible description by concatenating the text alternatives for elements referenced by an aria-describedby attribute on the current element. The text alternatives for the referenced elements are computed using a number of methods, outlined below in the section titled Accessible Name and Description Computation.

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The following table provides the order of precedence for markup that can be applied to compute an accessible description. User agents MUST use the first applicable entry from the table where the listed conditions are met, as described in the last column. The user agent MUST NOT use any markup other that the first relevant markup found, even if that markup results in an empty description:

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Precedence	Attribute	Applicable conditions	How used to compute description
1	`aria-describedby` attribute	Use on any element	Text content computation on all nodes referenced by aria-describedby on the element, concatenated, and separated by a space character
2	`aria-description` attribute	Use on any element	As a flat string
3	host language features which participate in the description calculation	` `` `242` `+ Unique host language features MAY participate in the description computation for an element, only if they were not already used ` `` `243` `+ for the accessible name of the applicable element. See HTML AAM: Accessible Description Computation ` `` `244` `+ for the HTML elements which meet this condition. ` `` `245` `+	` `` `247` `+ Either a text equivalent computation of the element, or as a flat string of the attribute's value. ` `` `248` `+
4	host language tooltip attribute or equivalent feature (e.g., HTML `title` attribute)	` `` `254` `+ ` `` `255` `+ Any element ` `` `256` `+ Only use if not already used for the accessible name of this node ` `` `257` `+ ` `` `258` `+	As a flat string

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Accessible Name and Description Computation

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The accessible name and description computation is used to generate both the accessible name and accessible description. There are different rules provided for several different types of [=element|elements=], [=nodes=], and combinations of markup. Text alternatives are built up, when appropriate, from all the relevant content contained within an [=element=]. This is accomplished via steps 2B and 2F, which are recursive, using the full set of rules to retrieve text from its own children or nodes it references.

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Text Equivalent Computation

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The text equivalent computation is used by both the accessible name and accessible description. There are different rules provided for several different types of [=element|elements=], [=nodes=], and combinations of markup. Text alternatives are built up, when appropriate, from all the relevant content contained within an [=element=]. This is accomplished via steps 2B and 2F, which are recursive, using the full set of rules to retrieve text from its own children or nodes it references.

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The purpose of the computation is to create a perceivable label or description for alternative presentations, in the form of a flat string of space separated textual tokens.

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Terminology

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Computation steps

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Otherwise:

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if computing a name, and the current node has an aria-labelledby [=attribute=] that contains at least one valid IDREF, and the current node is not already part of an aria-labelledby traversal, process its IDREFs in the order they occur:

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or, if computing a description, and the current node has an aria-describedby [=attribute=] that contains at least one valid IDREF, and the current node is not already part of an aria-describedby traversal, process its IDREFs in the order they occur:
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``

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if the current node has an aria-labelledby [=attribute=] that contains at least one valid IDREF, and the current node is not already part of an ongoing aria-labelledby or aria-describedby traversal, process its IDREFs in the order they occur:

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Set the accumulated text to the empty string.

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For each IDREF:

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Computation steps

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<div role="checkbox" aria-checked="false">Flash the screen <span role="textbox" aria-multiline="false"> 5 </span> times</div>

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Otherwise, if computing a name, and if the current node has an aria-label [=attribute=] whose value is not undefined, not the empty string, nor, when trimmed of [=ascii whitespace|whitespace=], is not the empty string:
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Otherwise, if the current node has an aria-label [=attribute=] whose value is not undefined, not the empty string, nor, when trimmed of [=ascii whitespace|whitespace=], is not the empty string:
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- If traversal of the current node is due to recursion and the current node is an embedded control as defined in step 2C, ignore aria-label and skip to rule 2C.
- Otherwise, return the value of aria-label.