Hello,
PMSessionValidatePrintSettings return always "false" on macOS
PMPrintSettings settings;
PMPrintSession session;
Boolean result;
PMCreateSession(&session);
PMSessionSetCurrentPMPrinter(session, printer);
PMCreatePrintSettings(&settings);
PMSessionDefaultPrintSettings(session, settings);
PMSetDuplex(settings, kPMDuplexTumble);
PMSessionValidatePrintSettings(session, settings, &result);
PMRelease(session);
PMRelease(settings);
if (result) NSLog (@"%@", @"changed");
else NSLog (@"%@", @"not changed");
Thanks