Thursday, September 5, 2013

Accessible Mozilla: Tech overview of Firefox 25


* We don't map aria-atomic:false to accessibility API anymore (see bug). UAIG is flexible on this and allows a fork in implementation: either ignore it or map it. Ignoring seems more reasonable so we did it this way. And here's why. Assistive technology relies on container-atomic object attribute exposed on every child of atomic region. In other words if there's no container-atomic object attribute then the accessible is not contained by atomic region. It's worth to notice it works pretty well if the users deals with nested aria-atomic regions, i.e. when atomic regions contain not atomic areas.

* We've got smarter about accessible tree creation, we started to ignore whitespace accessibles between ARIA grid cells (see bug). These whitespaces can be unintentionally introduced by the author when he creates the web page. They serve the pure layout job like they add some visual space between cells. What's worse any whitespaces are not expected under the grid control hierarchy and thus can confuse the assistive technology.

* ARIA column and row headers are not selectable by default anymore. Technically speaking if you do not specify aria-selected then SELECTABLE state is not exposed (see bug). The idea behind that is ARIA column/row headers are either not interactive at all or they are used to select the whole column/row at once.

* ARIA textbox exposes accessible value constructed from the content beneath the element (see bug).

* ARIA tablist is no longer a live region (see bug). The bug popped up from the wild: the users run into the problem. So we've got the bug fixed and asked for an update to UAIG spec.

* ARIA listbox exposes FOCUSABLE state regardless how it manages its children. That means if the listbox is not DOM focusable and its items are focusable instead (tabindex on items approach) then we enforce FOCUSABLE state on the listbox accessible. The trick is primarily introduced for MSAA environment where screen readers relies on FOCUSABLE state to differentiate HTML:ul from HTML:select since they share same MSAA role (see bug).

* ARIA treegrid like ARIA grid are editable by default now (see bug).

* In some cases we didn't treat 'undefined' value as absent value, for example, ARIA checkbox with aria-checked="undefined" was marked as not checkable. We fixed it.


longdesc attribute is exposed in Firefox context menu (see bug) as "View description" menu item. Right click on the image having a longdesc allows you to see it in new tab.

Text interface

A major change in this release is ATK and IAccessible text traversal by lines got a new heart. We still observe some problems (and even some serious ones) but definitely it must be a good update.


* We started to fire SELECTION state_change evens on items of selectable widgets like combobox or listbox (see bug). On MSAA level these events are partially duped by selection event but having only it AT had no way to detect which items was deselected.

* We fixed a nasty focus bug observed at start page: we missed the focus event when search textbox is moved through the page (see bug).

* In case of HTML checkbox input we fire state_change event whenever checkbox value is changed (previously we were restricted to user interactions), see bug.

Anything else

* We fixed hit testing for Firefox UI menus and popup (see bug) on Windows. Now each menu and popup hosted in own window returns HWND of that window and when the window receives WM_GET_OBJECT message then it answers it by returning the menu/popup accessible. If you take a hit test on the returned accessible then you get kids of menus/popups.

* We've got rid of XPCOM constant BOUNDARY_ATTRIBUTE_RANGE. It doesn't seem useful and practical.

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