Accessible Name and Description Computation 1.2

3.3.1 Terminology

Root node

The DOM node or element for which the text alternative is sought.

Current node

The DOM node currently traversed to compute the root node 's text equivalent. Initially, the current node is the root node , but at later stages is either some descendant of the root node , or another referenced node.

Flat string

A string of characters where all carriage returns, newlines, tabs, and form-feeds are replaced with a single space, and multiple spaces are reduced to a single space. The string contains only character data; it does not contain any markup.

Total accumulated text

The text equivalent computed up to, but not including the current node .

Accumulated text

Text accumulated at a step or sequence of steps described below. It is temporary storage for those steps.

Result

The text equivalent computed at one of the steps described below.

Append the result, without a space, to X

• If X is empty, copy the result to X.
• If X is non-empty, copy the result to the end of X.

Append the result, with a space, to X

• If X is empty, copy the result to X.
• If X is non-empty, add a space to the end of X and then copy the result to X after the space.

Prepend result, without a space, to X

• If X is empty, copy the result to X.
• If X is non-empty, copy the result to the start of X.

Prepend the result, with a space, to X

• If X is empty, copy the result to X.
• If X is non-empty, copy the result to the start of X, and add a space after the copy.

3.3.2 Computation steps

The text alternative for a given element is computed as follows:

1. Set the root node to the given element, the current node to the root node , and the total accumulated text to the empty string (""). If the root node 's role prohibits naming, return the empty string ("").
2. Compute the text alternative for the current node :
   1. If the current node is hidden and is not directly referenced by aria-labelledby or aria-describedby , nor directly referenced by a native host language text alternative element (e.g. label in HTML ) or attribute , return the empty string.
      Comment:

      By default, assistive technologies do not relay hidden information, but an author can explicitly override that and include hidden text as part of the accessible name or accessible description by using aria-labelledby or aria-describedby .

   2. Otherwise:
      • 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:
      • 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:
        1. Set the accumulated text to the empty string.
        2. For each IDREF:
           1. Set the current node to the node referenced by the IDREF.
           2. Compute the text alternative of the current node beginning with using the following steps:
              • If the current node is being rendered , recursively skip to step 2.
              • If the current node is not being rendered :
                1. If the current node has an aria-label attribute whose value, when trimmed of white space, is not the empty string, return the value of aria-label .
                2. Otherwise, return the innerText of the node.
              Set the result to that the computed text alternative. alternative from this step.
           3. Append the result , with a space, to the accumulated text .
        3. Return the accumulated text .
      Example:

      The following example shows the meaning of the clause "… and the current node is not already part of an aria-labelledby traversal …" .

      • element1 's accessible name is "hello" because this is a first traversal of its aria-labelledby , leading to element3 .
      • element2 has no accessible name . The computation involves a first traversal of its aria-labelledby leading to element1 , but element1 's aria-labelledby is not subsequently followed.

      Example 1

      <element1 id="el1" aria-labelledby="el3" />
      <element2 id="el2" aria-labelledby="el1" />
      
      <
      
      element3
      
      
      id
      
      =
      
      "el3"
      
      >
      
      hello
      
      </
      
      element3
      
      >
      
      
      

   3. Otherwise, if the current node is a control embedded within the label (e.g. the label element in HTML or any element directly referenced by aria-labelledby ) for another widget , where the user can adjust the embedded control's value, then return the embedded control as part of the text alternative in the following manner:
      • If the embedded control has role textbox , return its value.
      • If the embedded control has role combobox or listbox , return the text alternative of the chosen option .
      • If the embedded control has role range (e.g., a spinbutton or slider ):
        • If the aria-valuetext property is present, return its value,
        • Otherwise, if the aria-valuenow property is present, return its value,
        • Otherwise, use the value as specified by a host language attribute.
      Example:

      Consider a check box label that contains a text input field: "Flash the screen [input] times". If the user has entered "5" for the embedded textbox , the complete label is "Flash the screen 5 times", e.g.:

      Example 2

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

   4. Otherwise, if computing a name , and if the current node has an aria-label attribute whose value is not the empty string, nor, when trimmed of white space, is not the empty string:
      • If traversal of the current node is due to recursion and the current node is an embedded control as defined in step 2E, ignore aria-label and skip to rule 2E.
      • Otherwise, return the value of aria-label .
      Example:

      The following example shows the interaction of aria-labelledby and aria-label when a node has an aria-labelledby that refers to itself. The <span role="button"> elements have the accessible names "Delete Documentation.pdf" and "Delete HolidayLetter.pdf", respectively.

      Example 3

      <h1>Files</h1>
      <ul>
        <li>
          <a id="file_row1" href="./files/Documentation.pdf">Documentation.pdf</a>
          <span role="button" tabindex="0" id="del_row1" aria-label="Delete" aria-labelledby="del_row1 file_row1"></span>
        </li>
        <li>
          <a id="file_row2" href="./files/HolidayLetter.pdf">HolidayLetter.pdf</a>
          <span role="button" tabindex="0" id="del_row2" aria-label="Delete" aria-labelledby="del_row2 file_row2"></span>
        </li>
      
      </
      
      ul
      
      >
      
      
      

   5. Otherwise, if the current node 's native markup provides an attribute (e.g. alt ) or element (e.g. HTML label or SVG title ) that defines a text alternative, return that alternative in the form of a flat string as defined by the host language, unless the element is marked as presentational ( role="presentation" or role="none" ).
      Note

      See HTML -AAM , SVG -AAM , or other host language documentation for more information on markup that defines a text alternative.
      Comment:

      For example, in HTML , the img element's alt attribute defines a text alternative string, and the label element provides text for the referenced form element. In SVG2 , the desc and title elements provide a description of their parent element.

   6. Otherwise, if the current node's role allows name from content , or if the current node is referenced by aria-labelledby , aria-describedby , or is a native host language text alternative element (e.g. label in HTML ), or is a descendant of a native host language text alternative element :
      1. Set the accumulated text to the empty string.
      2. Check for CSS generated textual content associated with the current node and include it in the accumulated text . The CSS :before and :after pseudo elements [ CSS2 ] can provide textual content for elements that have a content model.
         • For :before pseudo elements, User agents MUST prepend CSS textual content, without a space, to the textual content of the current node .
         • For :after pseudo elements, User agents MUST append CSS textual content, without a space, to the textual content of the current node .
      3. For each child node of the current node :
         1. Set the current node to the child node.
         2. Compute the text alternative of the current node beginning with step 2. Set the result to that text alternative.
         3. Append the result to the accumulated text .
      4. Return the accumulated text .

      Important : Each node in the subtree is consulted only once. If text has been collected from a descendant, but is referenced by another IDREF in some descendant node, then that second, or subsequent, reference is not followed. This is done to avoid infinite loops.

      Comment:

      This step can apply to the child nodes themselves, which means the computation is recursive and results in text collected from all the elements in the current node 's subtree, no matter how deep it is. However, any given descendant node 's text alternative can result from higher precedent markup described in steps B through D above, where "Namefrom: author" attributes provide the text alternative for the entire subtree.

   7. Otherwise, if the current node is a Text node , return its textual contents.
   8. Otherwise, if the current node is a descendant of an element whose Accessible Name or Accessible Description is being computed, and contains descendants, proceed to 2F.i.
   9. Otherwise, if the current node has a Tooltip attribute , return its value.
      Comment:

      Tooltip attributes are used only if nothing else, including subtree content, has provided results.

   Append the result of each step above, with a space, to the total accumulated text .

After all steps are completed, the total accumulated text is used as the accessible name or accessible description of the element that initiated the computation.