- Sticky keys
Allows for a key combination like Ctrl+Alt+F9 to be entered sequentially.
- Repeat keys
Ignore long presses of the same key and control the repeat rate of the key presses.
- Bounce keys
Ignore repeated presses of the same key.
- Slow keys
Specify the duration for which you must press-and-hold a key before the system accepts the key press.
- Toggle keys
Emit an audible notification when a user activates or deactivates a toggle key.
- Mouse keys
Use the numeric keypad to emulate mouse actions.
- High Contrast/Large Print Desktop Themes
Implement such themes to aid visual impairedness.
- Screen Reader
A software application that enables people with severe visual impairments to use a compute. They provide information about icons, menus, dialogue boxes, files and folders.
Two ways to provide this information:
Speech A Text-To-Speech (TTS) engine to translate on-screen information into speech - output through earphones or speakers. Maybe hardware or software.
Braille An external hardware device - a refreshable Braille display. Contains one or more rows of cells. Each cell can be formed into the shape of a Braille character. Braille characters change as the video display changes. Braille and speech are often used together.
- Screen Magnifier
Does as the name suggests. Standalone applications now being replaced with Orca.
A screen reader for Gnome. Lets users access to information not easily reachable through keyboard navigation commands.
It defines a set of default behaviours (reaction to application events) and key bindings (reaction to user key presses).
An on-screen keyboard that provides
- access to the GNOME desktop via dynamically generated keyboards
- text entry via one of the provided alphanumeric keyboards
- text entry via a dynamic keyboard created based on the users current system keyboard driver
- user made keyboardtext entry
- gui interaction using only switches and/or mouse devices.
Allow pre-defined mouse movements to run/startup applications. The mouse stroke is associated with a command.
A speech interface that allows visually impaired users to interact independently and efficiently with the computer
A program the provides various keyboard enhancements, such as StickKeys, MouseKeys, and BounceKeys. Provides two programs:
- accessx GUI configuration tool. Enables settings on exit. Stores settings in ~/AccessX or somewhere in the users home directory.
ax Command-line version of accessx. Also loads the user preferences without opening a terminal. Used to automate startup - add ax to ~/.xsessions file. ~/AccessX file takes the same format as Xresources.
Sample ~/AccessX configuration entries
*TimeOutScale.value: 2 *StickyKeysToggle.set: False *MouseKeysToggle.set: False *ToggleKeysToggle.set: False *RepeatKeysToggle.set: True *SlowKeysToggle.set: False *BounceKeysToggle.set: False *StickyTwoKeysToggle.set: True *StickyModSoundToggle.set: True *MouseMaxSpeedScale.minimum: 1 ..... *KRGDebounceScale.value: 3
- Technology, terminology
- Gnome Accessible Technology (AT) support
- These notes are based on v2.18 docs.
- GDM supports "Accessible Login" and AT programs such as GOK (on-screen keyboard) and orca (magnifier and text-to-speech).
- 'gdmsetup' does not yet work with accessibility -> need to manually edit ascii files
- /usr/share/gdm/autostart/LoginWindow directory contains files in the format specified by the "FreeDesktop.org Desktop Application Autostart Specification".
- Any .desktop files in this directory will cause the associated program to automatically start with the login GUI greeter.
- best use 'gdmlogin' for both greeters.
- the GDM greeter programs support the ability to launch AT's at login time via configurable "gestures".
- these gestures can be defined to be standard keyboard hotkeys, switch device event or mouse motion events.
- when using the "GTK+ Greeter" the user may also change the visual appearance of the login UI - use a higher-contrast color scheme for better visibility.
Greeter statements in /etc/gdm/gdm.conf-custom
[daemon] Greeter=/usr/lib/gdmlogin RemoteGreeter=/usr/lib/gdmlogin
Configure gestures entries in- /etc/gdm/gdm.conf-custom
[daemon] AllowThemeChange=true # Allow users to change the color and # contrast scheme of the login dialog GtkThemesToAllow=HighContrast,HighContrastInverse # Restrict users to this list of themes AddGtkModules=true # Enables use of ATs - Onscreen # Keyboard, Screen Reader or Magnifier GtkModulesList=gail:atk-bridge:/usr/lib/gtk-2.0/modules/ \ libkeymouselistener:/usr/lib/gtk-2.0/modules/libdwellmouselistener
Last line causes all GDM GUI programs to be run with the appropriate GTK modules for launching AT programs - allowing user to enable them through the login screen.
Gesture associations are contained in files AccessKeyMouseEvents and AccessDwellMouseEvents.
$ ls /etc/gdm/modules AccessDwellMouseEvents AccessKeyMouseEvents \ factory-AccessDwellMouseEvents factory-AccessKeyMouseEvents
- GDM GConf AT keys
GDM offers GConf keys to control its accessibility features:
Key Value Description /desktop/gnome/interface/accessibility false (boolean) Controls whether the Accessibility infrastructure will be started with the 'gdm'. This is needed for many accessibility technology programs to work. /desktop/gnome/applications/at/screen_magnifier_enabled false (boolean) If true starts with 'gdm'. /desktop/gnome/applications/at/screen_keyboard_enabled false (boolean) If true enables with 'gdm', enables On-screen keyboard. /desktop/gnome/applications/at/screen_reader_enabled false (boolean) If true starts with 'gdm', enables screen reader.
- Linking GConf Keys to ATs
- The assistive tool that gets launched depends on the desktop files located in the GDM autostart directory.
- Any desktop file in the GDM autostart directory can be linked to these GConf keys via specifying that GConf key in the AutostartCondition value in the desktop file.
- The 'AutostartCondition' line in the desktop file could be one of the following
AutostartCondition=GNOME /desktop/gnome/applications/at/screen_keyboard_enabled AutostartCondition=GNOME /desktop/gnome/applications/at/screen_magnifier_enabled AutostartCondition=GNOME /desktop/gnome/applications/at/screen_reader_enabled
- When an accessibility key is true any program which is linked to that key in a GDM autostart desktop file will be launched (unless the Hidden key is set to true in that desktop file).
- A single GConf key can start multiple assistive tools if there are multiple desktop files with this AutostartCondition in the GDM autostart directory.
- Change an AT configuration
- The modification
Replace GOK with the on-screen keyboard application "onboard" and additionally activate the assistive tool "mousetweaks" for dwelling support.
(1) Create two desktop files, one for onboard and a second for mousetweaks e.g.
- onboard.desktop and
(2) Place them in the GDM autostart directory (/usr/share/gdm/autostart/LoginWindow).
[Desktop Entry] Encoding=UTF-8 Name=Onboard Onscreen Keyboard Comment=Use an on-screen keyboard TryExec=onboard Exec=onboard --size 500x180 -x 20 -y 10 Terminal=false Type=Application StartupNotify=true Categories=GNOME;GTK;Accessibility; AutostartCondition=GNOME /desktop/gnome/applications/at/screen_keyboard_enabled
[Desktop Entry] Encoding=UTF-8 Name=Software Mouse-Clicks Comment=Perform clicks by dwelling with the pointer TryExec=mousetweaks Exec=mousetweaks --enable-dwell -m window -c -x 20 -y 240 Terminal=false Type=Application StartupNotify=true Categories=GNOME;GTK;Accessibility; AutostartCondition=GNOME /desktop/gnome/applications/at/screen_keyboard_enabled
The line with the AutostartCondition links both desktop files to the GConf key for the on-screen keyboard.
Disable GOK from starting
Remove or deactivate the desktop file for the GOK on-screen keyboard by either
- removing the gok.desktop file from the GDM autostart directory or
- adding the Hidden=true key setting to the gok.desktop file.
GOK will no longer be started when the user activates the on-screen keyboard in the GDM session, onboard and mousetweaks will be.