Qt AT-SPI 2 Bridge

The Qt AT-SPI 2 bridge (Assistive Technology Service Provider Interface) is a Qt Accessibility plugin that exposes the internals of a Qt application to accessibility clients such as screen readers.

Source code

The source code for the bridge is archived on KDE Invent following the closure of the original Gitorious repository^[1] by the Qt developers in 2016.

Tools

Thanks to the efforts of the GNOME Project to implement their AT-SPI 2 implementation (named ATK, the Accessibility ToolKit), we have some really helpful tools for further development in this area:

Accerciser, an interactive accessibility explorer written in Python.
Orca, an extensible screen reader that converts textual content into speech and/or braille.
"Python-powered" Accessibility code example.

Testing/Development

Development of these components requires a very recent environment, most notably to include:

Inside a GNOME session, the accessibility software and other assistive technology (often referred to by the numeronym a11y) use a dedicated D-Bus, so if you want to monitor what is going on you should use a tool like dbus-monitor:

dbus-monitor --address $(xprop -root | grep AT_SPI_BUS | sed -e 's/.*= "//' -e 's/"$//')

To do

Complex widgets with children? Tabs … clicking on a file in qgit … (crash fix committed, but still needs proper fix)

GetApplicationBusAddress seems to be undefined in the XML, but is actually called mgorse[sic, ??], that ought to be defined somewhere. It is used to try to set up a direct D-Bus connection between libatspi and the application. libatspi will revert to using the session bus if it returns an empty string or an error.

Don't pretend to be gail, instead coordinate with the Orca developers
Test apps with multiple windows
Fix action for menus inside Qt
Scroll bars have a value interface, but don't update and cannot be updated, value interface in general…
Text attributes (bold, etc.)
Tabs

Widgets

Combobox
List
Tree
Table
Spinner
Scrollbar

**KDE Widgets**
Widget	Status
ExampleWidget1	Ready.
ExampleWidget2	Mostly done, still needs fooBar() call.
KCharSelect	Unknown
KColorButton	Unknown
KColorCombo	Unknown
KComboBox	Unknown
KCModule	Unknown
KDateWidget	Unknown
KDatePicker	Unknown
KDialog	Unknown
KEditListBox	Unknown
KFontComboBox	Unknown
KFontChooser	Unknown
KFontRequester	Unknown
KGradientSelector	Unknown
KHistoryComboBox	Unknown
KHueSaturationSelector	Unknown
KHtmlView	Unknown
KLed	Unknown
KListWidget	Unknown
KLineEdit	Unknown
KPushButton	Unknown
KRestrictedLine	Unknown
KIntSpinBox	Unknown
KRuler	Unknown
KSqueezedTextLabel	Unknown
KTextBrowser	Unknown
KTextEdit	Unknown
KURLLabel	Unknown
KURLComboRequester	Unknown
KURLRequester	Unknown
KIntNumInput	Unknown
KDoubleNumInput	Unknown
KDateTimeWidget	Unknown
KDateTable	Unknown

Memory Management

Qt's current QAccessibleInterface is a pain to deal with.

We can only (safely?) hold on to interfaces created by navigate or queryInterface.
Interfaces that we get through notifyAccessibility are deleted by Qt behind our back, so we need to never keep those around (Frederik will try to fix that now).

References

↑ Formerly accessible at git://gitorious.org/qt-at-spi.git.

External links

KDE Accessibility tutorial on Techbase
AT-SPI2 on Freedesktop.org Wiki
Linux Foundation's ATK/AT-SPI Special Interest Group
- AT-SPI on D-Bus (last updated on June 1, 2011)

[gitorious-1] Formerly accessible at git://gitorious.org/qt-at-spi.git.

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