Mobility impairments can be caused by arthritis, stroke, cerebral palsy, Parkinson's disease, multiple sclerosis, and loss of limbs or digits, among others. Poor muscle control or weakness can make using standard keyboards and mouse devices difficult. For instance, some people are unable to type two keys simultaneously, while others tend to hit multiple keys or to bounce keys when pressing or releasing them. People who are able to use only one hand likewise have difficulties with some keyboard and mouse tasks. The technologies which can assist those with mobility impairments are: On-Screen Keyboard - lets users select keys using a pointing method such as pointing devices, switches, or Morse-code input systems. Mouse and Keyboard Enhancements - helpful for users who have trouble typing and controlling a mouse or a keyboard.

On-Screen Keyboard GOK The On-Screen Keyboard application displays virtual keyboards on your desktop. You can use the standard mouse pointer or alternative pointing device to operate the virtual keyboards. On-Screen Keyboard displays the following types of keyboards: Composer Keyboards enable you to compose text. To type alphanumeric characters, you select the characters on the composer keyboard. Dynamic Keyboards reflect the applications that are currently running on the desktop. For example, On-Screen Keyboard generates dynamic keyboards that contain keys to represent the applications that are running on your desktop or the menus that are contained in an application. To start On-Screen Keyboard, choose Applications Accessibility On-Screen Keyboard . For more information about the On-Screen Keyboard application, see the Help for On-Screen Keyboard.

maximizing Terminal On-Screen Keyboard If you are an On-Screen Keyboard user, you cannot use any application in Full-Screen mode because the application window obscures the On-Screen Keyboard display. To resize the window for use with the On-Screen Keyboard application, perform the following steps: Do not enable the Full-Screen mode in the application. Give focus to the application window. Press F10 to maximize the application.

This section describes how to configure the mouse and keyboard to make these devices accessible to more users.

Use the Mouse preference tool to configure the mouse to suit your needs. To open the Mouse preference tool, choose SystemPreferencesMouse . The Mouse Preferences dialog is displayed.

The following sections describe how to modify the behavior of the mouse to suit your needs.

mouse left hand To configure the mouse for left-handed use, click on the Buttons tab in the Mouse Preferences dialog, then select the Left-handed mouse option. When you select this option, the system swaps the functions of the left mouse button and the right mouse button immediately.

mouse double-click behavior If you have difficulty double-clicking, you can increase the period of time that the system allows to elapse between the first click and the second click of a double-click. For example, if the double-click timeout setting is 0.4 seconds, you must perform the second click of a double-click within 0.4 seconds of the first click. If the second click occurs more than 0.4 seconds after the first click, the system interprets the two clicks as two single clicks. To configure the double-click timeout setting, perform the following steps: Click on the Buttons tab in the Mouse Preferences dialog. Use the Timeout slider to specify the timeout in seconds that the system allows between the two clicks of a double-click. Moving the slider to the right will increase the timeout interval in 0.1 second intervals. In the same manner, moving the slider to the left will decrease the timeout in 0.1 second intervals. Double-click on the light bulb to the right of the slider to test the setting. If you perform the two clicks of the double-click within the timeout specified, the light bulb lights up fully to display a yellow glow around the bulb. If you do not double-click within the timeout specified, the light bulb does not light fully. You should increase the timeout setting and try again. When the light bulb lights, the timeout setting is suitable for your needs.

mouse pointer size pointer size To change the size of the mouse pointer that is displayed on the desktop, perform the following steps: Click on the Pointers tab in the Mouse Preferences dialog. This will display a list of pointer themes and sizes available. By default, GNOME does not include mouse pointer themes. Information about installing and using pointer themes can be found in the User Guide. On some platforms you must log out and log in again for this setting to take effect.

mouse locating pointer If you have difficulty locating the mouse pointer on the screen, you can enable an option to highlight the pointer when you press the Control key. To enable this option, click on the Pointers tab in the Mouse Preferences dialog, then select the Highlight the pointer when you press Ctrl option. When you press Control, the system displays an animation around the pointer to highlight the pointer. On some platforms, you must log out and log in again before this setting takes effect.

mouse speed and sensitivity To configure the speed and sensitivity of the mouse, perform the following steps: Click on the Motion tab in the Mouse Preferences dialog. Configure the following options: Acceleration Use the slider to specify the speed at which the mouse pointer moves around the screen when you move the mouse. If you select a low setting, the mouse pointer moves at a speed similar to the speed at which you are physically moving the mouse. This means that you need to physically move the mouse larger distances to cover the screen area. If you select a high setting, the mouse pointer moves at a faster speed than the speed at which you physically move the mouse. This means that you need to physically move the mouse small distances to cover the screen area. Sensitivity Use the slider to specify how responsive the mouse pointer is to movements of the mouse. Moving the slider to the right will increase the sensitivity and moving it to the left will decrease the sensitivity. Threshold Use the slider to specify the distance that you must move an item before the system interprets the move action as a drag-and-drop action.

cursor stop blinking The following section describes how to modify the display characteristics of the cursor.

To stop the cursor from blinking in text boxes and other areas, perform the following steps: Choose System PreferencesKeyboard to start the Keyboard preference tool. In the Keyboard tabbed section, deselect the Cursor blinks in text boxes and fields option.

If you have difficulty using a mouse, you can use the keyboard to emulate the mouse functions. See of this guide for more information.

Use the Keyboard preference tool to configure the keyboard accessibility options. To open the Keyboard preference tool, choose System Preferences Keyboard. Accessibility options can be enabled by selecting the Accessibility tab. The Accessibility tabbed section allows the following options: "Allow to turn accessibility features on and off from the keyboard" (Alt-A) - this determines if keyboard accessibility functions can be turned on or off with a key command. Simulate simultaneous keypresses (Alt-S) - allows multiple shift (or other) keys to be entered individually but processed as a single combination keystroke. This keyboard accessibility technique is known as "sticky keys." Disable sticky keys if two keys are pressed together (Alt-B) - automatically exit the sticky keys mode if any key combination is entered normally (eq, at the same time instead of entered individually). Only accept long keypresses (Alt-O) - in this mode, keys must be pressed for a given length of time before they are accepted as input. This accessibility technique is also known as "slow keys." This portion of the Accessibility tabbed section also supplies a Delay slider (Alt-D) to indicate the press-down delay before the key is accepted as input. Ignore fast duplicate keypresses (Alt-I) - in this mode, successive entry of the same key will only have a single instance of that key accepted as input. This accessibility technique is also known as "bounce keys." This portion of the Accessibility tabbed section also supplies a Delay slider (Alt-E) to indicate the press-down delay before successive keys are ignored.

Use the Keyboard preference tool to configure the keyboard to simulate a mouse. To open the Keyboard preference tool, choose System Preferences Keyboard. The Mouse Keys options can be enabled by selecting the Mouse Keys tab. "Allow to control the pointer using the keyboard" (Alt-A) - this determines if the keyboard can be used to control the mouse pointer. Acceleration (Alt-C) - determines how quickly mouse motion will accelerate when keyboard directional keys are pressed. Speed (Alt-S) - determines how quickly the mouse pointer will move when keyboard directional keys are pressed. Delay (Alt-D) - determines how much (or if) keypresses may be dampened or ignored when keyboard directional keys are pressed.

MouseTweaks is a collection of accessibility enhancements for pointing devices. The mousetweaks package provides the functions offered by the Accessibility tab of the Mouse preference tool. It also contains two panel applets related to the mouse accessibility. More particularly: It allows users to perform a secondary click by doing a click-and-hold of the primary mouse button. It offers a way to perform the various clicks without using any hardware button. In this context, the Dwell Click panel applet can be used to choose what click type to perform. It provides the Pointer Capture panel applet. This applet creates an area on the panel into which the pointer can be captured until the user releases it with a predefined button and modifier combination. Most mouse-related accessibility options can be found by using SystemPreferencesMouse and selecting the Accessibility tab. Two additional panel applets can optionally be added to the GNOME menu bar / system panel as well; see the sections below.

A secondary or right-click can be issued by using the primary button and keeping it held down for a specified delay.

A click can be issued by having the mouse pointer dwell in a given spot for a specified delay. In this mode, click-type is determined by the ClickType window, Dwell Click applet, or by the direction in which the user moves the mouse after the dwell time has elapsed. There is only a determined amount of time to move the mouse to indicate the click type; after that time has elapsed the pointer movement does not trigger a click until after the dwell time of the next pointer stop. The click-type can be single, double, drag or right. The Dwell Click panel applet can be enabled by right-clicking the GNOME Desktop menu bar / system panel, selecting Add to Panel, choosing Dwell Click and clicking the Add button.

The mouse pointer can be locked into an area of the screen so the pointing device is free for other tasks. The Pointer Capture panel applet creates such an area on the panel, into which the user can lock the pointer until released in a determined way. The Pointer Capture panel applet can be enabled by right-clicking the GNOME Desktop menu bar / system panel, selecting Add to Panel, choosing Pointer Capture and clicking the Add button. Preferences may be set by choosing Preferences in the context menu of the Pointer Capture applet: In the Capture Pointer section, the user can specify under what circumstances the pointer gets captured when it moves into the capture area. For example, if the Ctrl modifier key is checked, the pointer gets captured when it is over the capture area and the user presses the Ctrl modifier key. If no modifier is checked and the mouse button is set to 0, the pointer only has to move into the capture area to get locked. It is also possible to specify a combination of modifiers with the chosen mouse button. In the Release Pointer section, the user can specify what modifier or mouse button releases the pointer. It is also possible to specify a combination of modifiers with the chosen mouse button. In the Size of Capture Area section, the user can specify the width of the capture area on the GNOME panel.