XUL Accessibility 编辑

Introduction

This article shows how XUL control elements are mapped to accessibility API. It is much in progress.

This section holds some rules applied to generating accessible name and description.

if the child node is hidden then it's ignored excepting the case when the element used as label is hidden itself
If the child node is text node then its rendered value is appended
If the child node is element then
- if it implements nsIDOMXULLabeledControlElement then the value of label property is appended
- otherwise
  - if it's a label element then then value attribute is appended
  - otherwise append tooltiptext attribute
- append the accessible value

search inside the element subtree
go up through parents (max level is 5) and search inside theirs subtrees
if the element is anonymous then search in whole anonymous subtree, here the attribute anonid is used instead of id attribute

This section describes common rules how accessibility properties are formed for XUL elements.

The following rules to generate accessible name are applied:

check aria-labelledby attribute, name is generated from elements pointed by aria-labelledby attribute

<description id="descr1">label1</description>
<description id="descr2">label2</description>
<textbox aria-labelledby="descr1 descr2" />

if the element implements nsIDOMXULLabeledControlElement or nsIDOMXULSelectControlItemElement interface then it is used label property
if the element doesn't implement nsIDOMXULSelectControlElement then label attribute is used
if neighbour of the element has label element pointing to this element by the control attribute, if the label element is found then use value attribute or its content.

<label value="it's label for control" control="control" />
<hbox role="grouping" id="control" />

get tooltiptext attribute
if the element is anonymous child of the element that is the direct child of toolbaritem element or the element is direct child of toolbaritem element then title attribute of toolbaritem element is used (currently it's used in Firefox UI only)
if the element has ARIA role and the role allows to aggregate name from subtree of element then generate name from subtree of the element

The following rules to generate accessible description are applied:

check aria-describedby attribute, description is generated from elements pointed by aria-describedby attribute

<description id="descr1">label1</description>
<description id="descr2">label2</description>
<textbox aria-describedby="descr1 descr2" />

if neighbour of the element has description element pointing to this element by the control attribute, if the description element is found then use its content.

<description value="it's label for control" control="control" />
<hbox role="grouping" id="control" />

If the ARIA role is used and it allows to have accessible value then aria-valuetext or aria-valuenow are used
If the element is XLink then value is generated from link location