Man page 3 : XkbLockModifiers

XkbLockModifiers - Locks and unlocks any of the eight real keyboard modifiers

Bool XkbLockModifiers (Display * display , unsigned int device_spec , unsigned int affect , unsigned int values );

• display
      connection to the X server
• device_spec
      device ID, or XkbUseCoreKbd
• affect
      mask of real modifiers whose lock state is to change
• values
      1 => lock, 0 => unlock; only for modifiers selected by affect

XkbLockModifierssends a request to the server to lock the real modifiers selected by both affectand valuesand to unlock the real modifiers selected by affect,but not selected by values. XkbLockModifiersdoes not wait for a reply from the server. It returns True if the request was sent, and False otherwise. The functions in this section that change the use of modifiers use a mask in the parameter affect. It is a bitwise inclusive OR of the legal modifier masks:

• True
                 The XkbLockModifiersfunction returns True if a request is sent to the server to lock the real modifiers selected by both affectand valuesand to unlock the real modifiers selected by affect,but not selected by values.
• False
                 The XkbLockModifiersfunction returns False if the request was not sent.