Added a diagnostic user message when enumerating printers fails. Also tweaked...

printing/backend/print_backend_cups.cc

 // Copyright (c) 2010 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>
@@ skipping 66 matching lines @@
 
 static const char kCUPSPrinterInfoOpt[] = "printer-info";
 static const char kCUPSPrinterStateOpt[] = "printer-state";
 
 class PrintBackendCUPS : public PrintBackend {
  public:
   PrintBackendCUPS(const GURL& print_server_url, bool blocking);
   virtual ~PrintBackendCUPS() {}
 
   // PrintBackend implementation.
-  virtual void EnumeratePrinters(PrinterList* printer_list);
+  virtual bool EnumeratePrinters(PrinterList* printer_list);
 
   virtual bool GetPrinterCapsAndDefaults(const std::string& printer_name,
                                          PrinterCapsAndDefaults* printer_info);
 
   virtual bool IsValidPrinter(const std::string& printer_name);
 
  private:
   // Following functions are wrappers around corresponding CUPS functions.
   // <functions>2()  are called when print server is specified, and plain
   // version in another case. There is an issue specifing CUPS_HTTP_DEFAULT
   // in the <functions>2(), it does not work in CUPS prior to 1.4.
   int GetDests(cups_dest_t** dests);
   FilePath GetPPD(const char* name);
 
   GURL print_server_url_;
   bool blocking_;
 };
 
 PrintBackendCUPS::PrintBackendCUPS(const GURL& print_server_url, bool blocking)
     : print_server_url_(print_server_url), blocking_(blocking) {
 }
 
-void PrintBackendCUPS::EnumeratePrinters(PrinterList* printer_list) {
+bool PrintBackendCUPS::EnumeratePrinters(PrinterList* printer_list) {
   DCHECK(printer_list);
   printer_list->clear();
 
   cups_dest_t* destinations = NULL;
   int num_dests = GetDests(&destinations);
+  // TODO(gene): Figure out how to get an error code from cupsGetDests so we can
+  // differentiate between the enumeration failing and there being 0 printers.
 
   for (int printer_index = 0; printer_index < num_dests; printer_index++) {
     const cups_dest_t& printer = destinations[printer_index];
 
     PrinterBasicInfo printer_info;
     printer_info.printer_name = printer.name;
 
     const char* info = cupsGetOption(kCUPSPrinterInfoOpt,
         printer.num_options, printer.options);
     if (info != NULL)
       printer_info.printer_description = info;
 
     const char* state = cupsGetOption(kCUPSPrinterStateOpt,
         printer.num_options, printer.options);
     if (state != NULL)
       base::StringToInt(state, &printer_info.printer_status);
 
     // Store printer options.
     for (int opt_index = 0; opt_index < printer.num_options; opt_index++) {
       printer_info.options[printer.options[opt_index].name] =
           printer.options[opt_index].value;
     }
 
     printer_list->push_back(printer_info);
   }
 
   cupsFreeDests(num_dests, destinations);
 
   VLOG(1) << "CUPS: Enumerated " << printer_list->size() << " printers.";
+  return true;
 }
 
 bool PrintBackendCUPS::GetPrinterCapsAndDefaults(
     const std::string& printer_name,
     PrinterCapsAndDefaults* printer_info) {
   DCHECK(printer_info);
 
   VLOG(1) << "CUPS: Getting Caps and Defaults for: " << printer_name;
 
   FilePath ppd_path(GetPPD(printer_name.c_str()));
@@ skipping 103 matching lines @@
                    << ", content length: " << content_len;
         file_util::Delete(ppd_path, false);
         ppd_path.clear();
       }
     }
   }
   return ppd_path;
 }
 
 }  // namespace printing