The function printer-port-supports-p detects if the printer port can support the feature named by feature .
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).
supportedp indicates if the feature is supported.
validp indicates if the feature was recognised.
Currently the only value of
feature
that is recognised is
:postscript
and the
supportedp
value is true if the printer supports PostScript.