Built-in Accessibility Features
The built-in accessibility features are extensions to the operating system.
These features affect the behavior of the system regardless of which applications
are running.
Win32 supports the following built-in accessibility features:
Feature
| Description
|
AccessTimeout
| Enables a user to specify a timeout interval after which system-wide
accessibility features are automatically disabled. The AccessTimeout feature is intended
for computers that are shared by several users with different preferences.
Each individual can use hot keys or the Control Panel to enable preferred
features. After a user leaves, the features he or she enabled will be automatically
disabled by the timeout. The accessibility features affected by the timeout are
FilterKeys, MouseKeys, StickyKeys, and ToggleKeys. The ACCESSTIMEOUT structure defines the parameters for this feature.
|
FilterKeys
| Enables control of keyboard properties, such as the amount of time before a
keystroke is accepted as input and the amount of time before a keystroke begins
to repeat. The FilterKeys feature also provides sound feedback when a key is
pressed and when it is accepted as input. The FILTERKEYS structure defines the parameters for this feature.
|
MouseKeys
| Enables the user to control the mouse pointer using the numeric keypad. The MOUSEKEYS structure defines the parameters for this feature.
|
SoundSentry
| Displays a visual signal when a sound is generated by a Windows-based
application or an MS-DOS application running in a window. The SOUNDSENTRY structure defines the parameters for this feature.
|
StickyKeys
| Enables the user to type key combinations, such as CTRL+ALT+DEL, in sequence rather than at the same time. The STICKYKEYS structure defines the parameters for this feature.
|
ToggleKeys
| Provides sound feedback when the user turns on or off the CAPS LOCK, NUM LOCK, or SCROLL LOCK keys. The TOGGLEKEYS structure defines the parameters for this feature.
|
The
SystemParametersInfo function provides the programming interface to the built-in accessibility
features. This function is useful in Control Panel applications or other programs
that allow the user to customize the Windows environment. The
SystemParametersInfo function can perform the following tasks:
- Query the system to determine the availability and current state of a
specified built-in accessibility feature
- Enable a feature and specify parameters that control its behavior
- Disable a feature
- Enable a hot key that allows the user to enable or disable a feature
For each of the built-in features, Win32 defines a structure that applications
use with
SystemParametersInfo to query or set the parameters of the feature.
An application can use
SystemParametersInfo to enable or disable a feature directly. For some of the features,
SystemParametersInfo can enable a hot key or key combination so the user can toggle the state of a
feature. There are no hot keys for the SoundSentry feature. The following
accessibility features have hot keys:
Feature
| Description
|
FilterKeys
| Hold down the LEFT SHIFT key for eight seconds to toggle the FilterKeys feature on or off. Holding
down the LEFT SHIFT key for 12 seconds enables FilterKeys using the most conservative values for FILTERKEYS.iBounceMSec. Holding down the LEFT SHIFT key for 16 seconds enables FilterKeys using the most conservative values for FILTERKEYS.iWaitMSec.
|
MouseKeys
| LEFT ALT+LEFT SHIFT+NUM LOCK
|
StickyKeys
| Press the SHIFT key 5 times
|
ToggleKeys
| Hold down the NUM LOCK key for 5 seconds
|
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