Bug 1663920 - Ignore CUPS_PRINTER_DISCOVERED, CUPS_PRINTER_FAX and CUPS_PRINTER_SCANNER in the CUPS backend. ?AlaskanEmily r=AlaskanEmily

Differential Revision: https://phabricator.services.mozilla.com/D90508

widget/nsPrinterListCUPS.cpp

@@ -39,12 +39,30 @@ nsTArray<PrinterInfo> nsPrinterListCUPS::Printers() const {
   nsTArray<PrinterInfo> printerInfoList;
 
   cups_dest_t* printers = nullptr;
+  // Ideally we should use cupsEnumDests with CUPS_PRINTER_DISCOVERED, etc.
+  // flags instead of calling cupsGetDests and filtering out
+  // CUPS_PRINTER_DISCOVERED later, because it should be faster than the
+  // cupsGetDests call.  That being said, unfortunately at least on Ubuntu 20.20
+  // cupsEnumDests doesn't filter out CUPS_PRINTER_DISCOVERED-ed printers at
+  // all. So for now we use cupsGetDests but if we still have perf issues when
+  // we enumerate available printers on Mac, we should use cupsEnumDest at least
+  // on Mac.
   auto numPrinters = sCupsShim.cupsGetDests(&printers);
   printerInfoList.SetCapacity(numPrinters);
 
   for (auto i : mozilla::IntegerRange(0, numPrinters)) {
     cups_dest_t* dest = printers + i;
 
+    if (const char* printerType = sCupsShim.cupsGetOption(
+            "printer-type", dest->num_options, dest->options)) {
+      nsresult rv;
+      int64_t type = nsAutoCString(printerType).ToInteger64(&rv);
+      if (NS_SUCCEEDED(rv) && (type & (CUPS_PRINTER_FAX | CUPS_PRINTER_SCANNER |
+                                       CUPS_PRINTER_DISCOVERED))) {
+        continue;
+      }
+    }
+
     cups_dest_t* ownedDest = nullptr;
     mozilla::DebugOnly<const int> numCopied =
         sCupsShim.cupsCopyDest(dest, 0, &ownedDest);