The function printer-port-handle
returns a platform-dependent value which represents the underlying handle to the printer port.
On Microsoft Windows, handle is the HDC for the printer device.
If port is passed it should be the value bound to var in with-print-job. If port is not supplied it defaults to the current printer port (dynamically bound within with-print-job).
CAPI User Guide and Reference Manual (Unix version) - 3 Aug 2017