Thursday, October 11, 2012

Firefox 16 - 18: what's new for AT developers

This summer wasn't super plenteous for features interesting for assistive technology developers. Firefox 17 was nearly barren in this sense. Thus here's a list of changes introduced in Firefox 16, Firefox 17 and Firefox 18.


(Firefox 16) ARIA documents are now subject of document loaded event. If the author does something like:

  <div id="dialog" role="dialog" style="display: none;">A message</div>
  document.getElementById("dialog").style.display = "block";

then LOAD_COMPLETE event is fired after the dialog appears (refer to document handling in Firefox for details).

(Firefox 17) We sorted out stuff related with vertical and horizontal states.  Previously we could expose these states on the same accessible the same time regardless the value of aria-orientation attribute or expose them on elements that orientation is not applied to. Also ARIA role="scrollbar" got vertical state as default value.

(Firefox 18) If ARIA grid contains role="rowgroup" then IAccessibleTable interface went crazy, i.e. row/col/cell indexes coherence was broken.

(Firefox 18) aria-activedescendant behavior was corrected a bit. We have supported the case the spec says about: "Authors MAY use the aria-activedescendant attribute on the focused descendant of a composite widget; for example, on a textbox descendant of a combo box." This is an example these words are applicable to.

  <div id="combobox" role="combobox">
    <input id="combobox_entry" />
      <li id="combobox_option1" role="option">option1</li>
      <li id="combobox_option2" role="option">option2</li>

If the input has DOM focus and the author changes the aria-activedescendant attribute on combobox element to point a combobox option then that combobox option gets the focus.

(Firefox 18) If ARIA role="presentation" is used on the element having ARIA global attributes or referred by ARIA relation then role="presentation" is ignored as it wasn't there. The behavior is similar if the element is focusable.


(Firefox 16) HTML5 article element is a subject of 'article' xml-roles object attribute.

Also we fixed few edge cases. Btw, they all were caught in the wild.

(Firefox 18) We didn't create a listitem accessible for HTML li element in some cases like:

  <ul id="list7">
    <li id="l7_li1" style="display:inline-block;">Oranges</li>
    <li id="l7_li2" style="display:inline; float: right;">Apples</li>

(Firefox 18) Table related styles used outside the table context prevented to create a correct accessible. For example,

  <h1 style="display: table-cell;">a header</h1>

didn't have a heading accessible.


(Firefox 18) Finally we sorted out invisible/offscreen states and the implementation corresponds to what I wrote before.

(Firefox 18) Some offscreen accessible didn't expose the offscreen state. You could see this bug at ai squared site.

Text attributes

(Firefox 16) auto-generated text attribute is supported now (refer to IAccessible2 spec). It's get exposed for auto generated CSS content (:after and :before pseudo elements) and HTML list bullets. Note, we don't expose the auto-generated object attribute anymore.


(Firefox 16) defaultKeyBinding attribute and getKeyBindings method of nsIAccessible interface was replaced on single accessKey attribute. Gecko always exposed either an access key (alt + letter) and/or keyboard shortcut (ctrl + letter). An ability to return many keybindings was never used.

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