The operating system sends the DBT_QUERYCHANGECONFIG device message to request permission to change the current configuration (dock or undock). Any application can deny this request and cancel the change.
To send the DBT_QUERYCHANGECONFIG device message, the operating system sends the WM_DEVICECHANGE message with wParam set to DBT_QUERYCHANGECONFIG and lParam set to zero.
Parameters
lParam
lParam is zero when the WM_DEVICECHANGE message is sent with wParam set to DBT_QUERYCHANGECONFIG.
Return Values
Return TRUE to grant permission to change the configuration.
Return BROADCAST_QUERY_DENY to deny permission to change the configuration.
See Also
DBT_CONFIGCHANGECANCELED, DBT_CONFIGCHANGED, WM_DEVICECHANGE