Setting Accessibility Time-out Periods

Article
06/30/2006

You should use the accessibility time-out option for computers that several users with different accessibility preferences share. Each user can use hot keys or the Accessibility Control Panel to enable preferred features. The accessibility time-out period is the length of time that must pass without keyboard or mouse input before the operating system (OS) automatically turns off accessibility features. The accessibility features that the time-out affects are mouse keys, sticky keys, toggle keys, and high contrast.

The user can control the settings for the accessibility time-out option by using the General tab of the Accessibility Control Panel application or another application for customizing the environment.

Applications use the SPI_GETACCESSTIMEOUT and SPI_SETACCESSTIMEOUT flags with the SystemParametersInfo function to get and set the accessibility time-out option. The ACCESSTIMEOUT structure defines the parameters for the accessibility time-out option. To set the accessibility time-out option, call SystemParametersInfo with the uiAction parameter set to SPI_SETACCESSTIMEMOUT, the uiParam parameter set to the size of the ACCESSTIMEOUT structure, and the pvParam parameter set to a pointer to an ACCESSTIMEOUT structure that contains the new time-out parameters that you want to use. You should set the ATF_TIMEOUTON flag in the dwFlags member of the ACCESSTIMEOUT structure that you pass to SystemParametersInfo and set the iTimeOutMSec member to the length of the time-out period in milliseconds.

The following code example shows how to set the accessibility time-out period to 10 minutes and how to specify that the OS should play a descending siren sound when the time-out period elapses and the OS turns off the accessibility options.

ACCESSTIMEOUT atf;
BOOL bSuccess;

// Fill in the members of the ACCESSTIMEOUT structure.

atf.cbSize = sizeof(ACCESSTIMEOUT);
atf.dwFlags = (ATF_ONOFFFEEDBACK | ATF_TIMEOUTON);
atf.iTimeOutMSec = 600000;

// Call SystemParametersInfo with the SPI_SETACCESSTIMEOUT flag. 

bSuccess = SystemParametersInfo(SPI_SETACCESSTIMEOUT, 
                                sizeof(ACCESSTIMEOUT), (LPVOID) &atf, 0);

To retrieve information about the time-out period, including whether a time-out period is set and the length of the time-out period, call SystemParametersInfo with uiAction set to SPI_GETACCESSTIMEOUT, uiParam set to the size of the ACCESSTIMEOUT structure, and pvParam set to a pointer to an ACCESSTIMEOUT structure. Examine the values of the members of the ACCESSTIMEOUT structure after SystemParametersInfo returns to obtain the information that you want about the accessibility time-out option.

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Setting Accessibility Time-out Periods

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