Most NPP functions return TRUE on success and FALSE to indicate failure. To provide more information when an error occurs, NPP functions can call the Win32 function SetLastError with an appropriate error code.
Print provider functions that take a printer or print server name as a parameter must return ERROR_INVALID_NAME if the print provider function determines that the specified printer or server does not exist on the network. This return value signals to the print request router (PRR) to pass the request on to the next print provider. Spooler calls that do not explicitly specify a handle to an open printer or server are handled by the PRR by passing the request to each print provider in turn until one accepts the request or all providers have failed.
Print provider functions that take a printer or server name as a parameter are: