The lockup hook is called when the system locks itself up. The following code shows the syntax for a lockup hook function:

BOOL EXPENTRY LockupHook (HAB  hab,
                          HWND hwndLockupFrame);

The hab parameter is the application anchor block.

The hwndLockupFrame parameter is the frame window of the lockup panel.

This function has no return value.

All HK_LOCKUP hooks registered with the system are called when the system locks itself up. All HK_LOCKUP hooks must be system hooks, not message queue hooks.

Application programs that create other lockup password input windows by hooking the HK_LOCKUP system hook can use WinUnlockSystem to force the system to unlock when another form of input is detected other than mouse or keyboard. For example, a pen gesture or some voice input or signature recognition.