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# Accessibility
Accessibility is important for a lot of users, without it they just can not use their computer.
<a href="http://www.insee.fr/fr/themes/document.asp?ref_id=ip1254#sommaire">“15% of the world's population lives with some form of disability”</a>
<a href="https://wiki.gnome.org/Accessibility/Laws">Laws require accessibility.</a>
## Principles
A few important principles are to be kept in mind
* We want to make existing software accessible, and avoid dedicated software
* We need synchronization: accessibility is just another way for input and output
* It should be easily available, ready to be enabled.
See also <a href="http://sonify.psych.gatech.edu/~walkerb/classes/assisttech/pdf/Mynatt(1994).pdf">Nonvisual Presentation of Graphical User Interfaces: Contrasting Two Approaches</a> which discusses a lot of ground design principles.
***
## TODO-list for Wayland
This is collected on [[Accessibility/Wayland/]]
***
## Revamping GTK accessibility stack?
This is collected on [[Accessibility/GTK-a11y-revamp/]]
***
## Input
Accessibility support is needed in [[Accessibility/Input/]]
***
## Output
Accessibility support is needed in [[Accessibility/Output/]]
***
## Toolkits
Accessibility support is needed in applications, through [[Accessibility/AT-SPI2/]]
[[!img at-spi.png align="center" alt="at-spi stack overview"]]
([[source|at-spi.fig]])
Toolkits can either implement the at-spi dbus protocol themselves (as is done by qt5), or use Atk to do the at-spi marshalling for them.
In such a case, a tree of objects with base class AtkObject can either
* be built along the toolkit widget tree (as is done externally and even lazily by java-atk-wrapper),
* or within the toolkit widget tree itself: for instance gtk's base GtkWindow object contains an AtkObject *accessible field, subclass initialization functions specify with gtk_widget_class_set_accessible_type which precise accessible type should be used, and gtk will eventually create the right AtkObject subclass in gtk_widget_real_get_accessible. For instance, GtkLabel's gtk_label_class_init calls gtk_widget_class_set_accessible_type (widget_class, GTK_TYPE_LABEL_ACCESSIBLE); to specify that it will use the GtkLabelAccessible class to implement accessibility.
In both case, atk glib interfaces (AtkComponent, AtkText, AtkSelection, etc.) are added to the AtkObject subclasses, to specify which at-spi interfaces are implemented. See for instance GtkAccessibleLabel's G_DEFINE_TYPE_WITH_CODE call.
A [[Accessibility/Walkthrough/]] documents the RPC and function calls details.
* GTK2/GTK3: good support, through [[atk|https://git.gnome.org/atk]] ([[documentation|https://developer.gnome.org/atk/]]), and atk-bridge from [[at-spi2-atk|https://git.gnome.org/at-spi2-atk/]]
* Qt5: improving, [[integrated in Qt5|http://doc.qt.io/qt-5/accessible.html]]
* Qt4: only preliminary support, through [[qt-at-spi|https://community.kde.org/Accessibility/qt-atspi]]
* wxWidgets: gtk-based widgets inherit gtk accessibility, wxWidgets-specific widgets have accessibility support on Windows, but missing a bridge on Linux, see [[https://www.wxwidgets.org/docs/tutorials/accessibility/]]
* Java: Basics, through [[java-atk-wrapper|https://wiki.gnome.org/Accessibility/JavaAtkWrapper]]
* Python Tkinter: Unmaintained [[https://pypi.org/project/Tka11y/]]
* WebKitGTK+: [[https://mariospr.org/2013/02/03/accessibility-in-webkitgtk/]]
When an application is composed of several processes (e.g. applets, separate web rendering, etc.), one can use AtkPlug and AtkSocket to make the applet accessibility tree magically appear in the accessibility tree of the application. See an instance on [[https://github.com/mariospr/atksocket-atkplug-example]]
Gnome provides an [[Accessibility development guide|https://developer.gnome.org/accessibility-devel-guide/]]
For ATK, there is [[a best ATK practices guide|https://wiki.gnome.org/Accessibility/ATK/BestPractices]] , and a minimal example of extending a base atk implementation is the GtkScaleAccessible class, based on GtkRangeAccessible, see gtk/gtk/a11y/gtkscaleaccessible.[ch]
For adding accessibility support to a custom-made widget, the [[evince implementation|https://git.gnome.org/browse/evince/tree/libview/ev-view-accessible.c#n71]] can be used as an example.
For Qt5, there is [[a guide for QWidget|http://doc.qt.io/qt-5/accessible-qwidget.html]] and [[a guide for Qt Quick|http://doc.qt.io/qt-5/accessible-qtquick.html]]
KDE provides an [[Accessibility development guide in the Human Interface Guidelines|https://hig.kde.org/accessibility/index.html]] , a [[Plasma Accessibility documentation|https://userbase.kde.org/Accessibility/Plasma]]
[[Plans for wayland|https://wiki.gnome.org/Projects/GTK%2B/Accessibility]]
To check the content exposed by application, use [[accerciser|https://wiki.gnome.org/Apps/Accerciser]]
LinuxJournal proposes a [[HOW-TO|https://www.linuxjournal.com/magazine/make-your-application-accessible-accerciser]]
## Screen reader side
For the screen reader side, one can read the [[libatspi documentation|https://www.manpagez.com/html/libatspi/]] or the pyatspi2 documentation available with `pydoc3 pyatspi`, there is also a [[small pyatspi2 example available|https://www.freedesktop.org/wiki/Accessibility/PyAtSpi2Example/]]
The main screen reader used on the desktop is [[Orca|https://wiki.gnome.org/Projects/Orca]], there is also an initial project called [[Odilia|https://odilia.app]]
Screen magnification is provided by gnome-shell or compiz' ezoom plugin.
## Lists
There are so many accessibility mailing lists, notably for each distribution:
* Debian [[https://lists.debian.org/debian-accessibility/]]
* Gentoo [[https://archives.gentoo.org/gentoo-accessibility/]], [[mailto:gentoo-accessibility@gentoo.org]]
* Slint [[https://www.freelists.org/list/slint]]
* Ubuntu [[https://lists.ubuntu.com/mailman/listinfo/ubuntu-accessibility]]
* Accessible Coconut [[https://groups.google.com/forum/#!forum/accessible-coconut]]
* Adriane [[http://www.blindzeln.net/mailman/listinfo/adriane-de]] , [[http://www.blindzeln.net/mailman/listinfo/adriane-de-dev]]
* F123e [[https://groups.io/g/F123e]]
* Perkify [[http://pa.cfcl.com/item?key=Areas/Content/Overviews/Perkify_Intro/main.toml]]
* Raspberry VI [[https://www.freelists.org/list/raspberry-vi]]
* Stormux [[https://groups.io/g/stormux]]
* Vinux [[http://groups.google.com/group/vinux-development]]
and for each toolkit or desktop:
* Gnome [[https://mail.gnome.org/mailman/listinfo/gnome-accessibility-devel]]
* KDE [[https://mail.kde.org/mailman/listinfo/kde-accessibility]]
* MATE [[https://groups.io/g/mate-accessibility]]
and for each screen reader:
* BRLTTY [[http://brltty.com/mailman/listinfo/brltty]]
* emacspeak [[https://www.cs.vassar.edu/~priestdo/emacspeak/]]
* fenrir [[https://www.freelists.org/list/fenrir-screenreader]]
* NVDA [[https://nvda.groups.io/g/nvda]] (for Windows, shares a few components with other screen readers)
* Orca [[https://mail.gnome.org/mailman/listinfo/orca-list]]
* speakup [[http://linux-speakup.org/cgi-bin/mailman/listinfo]]
* speech-dispatcher [[https://lists.nongnu.org/mailman/listinfo/speechd-discuss]]
and cross-software lists:
* blinux [[https://www.redhat.com/mailman/listinfo/blinux-list]]
* Freedesktop [[https://lists.freedesktop.org/mailman/listinfo/accessibility]]
* GNU [[https://lists.gnu.org/mailman/listinfo/accessibility]]
* Pinguin [[http://www.blindzeln.net/mailman/listinfo/pinguin]] (German)
* Carrefourblinux [[http://listengine.tuxfamily.org/lists.tuxfamily.org/carrefourblinux]] (french)
* ALLOS [[http://fr.groups.yahoo.com/group/ALLOS/]] (french)
* April accessibilite [[http://www.april.org/wws/arc/accessibilite]] (french)
If something is missing on these pages, don't hesitate to mail samuel.thibault@ens-lyon.org (or better, get a freedesktop wiki account to do additions yourself)
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