CUPS printing: Do not add scanners to the printer list.

printing/backend/print_backend_cups.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "printing/backend/print_backend.h"
 
 #include <dlfcn.h>
 #include <errno.h>
 #if !defined(OS_MACOSX)
 #include <gcrypt.h>
 #endif
 #include <pthread.h>
 
 #include "base/file_util.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/string_number_conversions.h"
 #include "base/synchronization/lock.h"
 #include "base/values.h"
 #include "googleurl/src/gurl.h"
 #include "printing/backend/cups_helper.h"
 #include "printing/backend/print_backend_consts.h"
 
-#if !defined(OS_MACOSX)
+#if defined(OS_MACOSX)
+// Mac still builds against the 10.5 SDK, which does not have this in cups.h.

[Mark Mentovai, 2011/08/08 21:02:07]

Don’t do this. You need more #if:

#if defined(OS_MACOSX)
#include <AvailabilityMacros.h>
#endif

#if defined(OS_MACOSX)
#if MAC_OS_X_VERSION_MAX_ALLOWED <= MAC_OS_X_VERSION_10_5
const int CUPS_PRINTER_SCANNER = 0x2000000;  // Scanner-only device
#endif
#else

That says “if the SDK is 10.5 or less, declare this…”

I’ve used const int because the system header uses an enum. Since it’s a named
enum, cups_ptype_e, we can’t add a new value to it here. A const int is closer
in spirit to a member of an enum than a #define is.

“Inserting” values into enums in this fashion is dangerous in light of certain
compiler optimizations. Be careful out there!

Note that I’ve also copied the comment from the system header. I consider this
important.

[Lei Zhang, 2011/08/08 22:04:02]

Mark: Thanks, more #ifs added.

On 2011/08/08 21:02:07, Mark Mentovai wrote:

+#define CUPS_PRINTER_SCANNER 0x2000000
+#else
 GCRY_THREAD_OPTION_PTHREAD_IMPL;
 
 namespace {
 
 // Init GCrypt library (needed for CUPS) using pthreads.
 // There exists a bug in CUPS library, where it crashed with: "ath.c:184:
 // _gcry_ath_mutex_lock: Assertion `*lock == ((ath_mutex_t) 0)' failed."
 // It happened when multiple threads tried printing simultaneously.
 // Google search for 'gnutls thread safety' provided a solution that
 // initialized gcrypt and gnutls.
@@ skipping 29 matching lines @@
     }
     if ((*pgnutls_global_init)() != 0)
       LOG(ERROR) << "Gnutls initialization failed";
   }
 };
 
 static base::LazyInstance<GcryptInitializer> g_gcrypt_initializer(
     base::LINKER_INITIALIZED);
 
 }  // namespace
-#endif
+#endif  // defined(OS_MACOSX)
 
 namespace printing {
 
 static const char kCUPSPrinterInfoOpt[] = "printer-info";
 static const char kCUPSPrinterStateOpt[] = "printer-state";
+static const char kCUPSPrinterTypeOpt[] = "printer-type";
 
 class PrintBackendCUPS : public PrintBackend {
  public:
   PrintBackendCUPS(const GURL& print_server_url, bool blocking);
   virtual ~PrintBackendCUPS() {}
 
   // PrintBackend implementation.
   virtual bool EnumeratePrinters(PrinterList* printer_list);
 
   virtual std::string GetDefaultPrinterName();
@@ skipping 29 matching lines @@
     VLOG(1) << "CP_CUPS: Error getting printers from CUPS server. Server: "
             << print_server_url_
             << " Error: "
             << static_cast<int>(cupsLastError());
     return false;
   }
 
   for (int printer_index = 0; printer_index < num_dests; printer_index++) {
     const cups_dest_t& printer = destinations[printer_index];
 
+    // CUPS can have 'printers' that are actually scanners. (not MFC)
+    // At least on Mac. Check for scanners and skip them.
+    const char* type_str = cupsGetOption(kCUPSPrinterTypeOpt,
+        printer.num_options, printer.options);
+    if (type_str != NULL) {
+      int type;
+      if (base::StringToInt(type_str, &type) && (type & CUPS_PRINTER_SCANNER))
+        continue;
+    }
+
     PrinterBasicInfo printer_info;
     printer_info.printer_name = printer.name;
     printer_info.is_default = printer.is_default;
 
     const char* info = cupsGetOption(kCUPSPrinterInfoOpt,
         printer.num_options, printer.options);
     if (info != NULL)
       printer_info.printer_description = info;
 
     const char* state = cupsGetOption(kCUPSPrinterStateOpt,
@@ skipping 139 matching lines @@
                    << ", HTTP error: " << http_error;
         file_util::Delete(ppd_path, false);
         ppd_path.clear();
       }
     }
   }
   return ppd_path;
 }
 
 }  // namespace printing