Make scoped dc objects smarter.

chrome/service/cloud_print/print_system_win.cc

 // Copyright (c) 2012 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 "chrome/service/cloud_print/print_system.h"
 
 #include <objidl.h>
 #include <winspool.h>
 #include <xpsprint.h>
 
@@ skipping 389 matching lines @@
           HRESULT hr = PrintTicketToDevMode(printer_name, print_ticket,
                                             &pt_dev_mode);
           if (FAILED(hr)) {
             NOTREACHED();
             return false;
           }
 
           HDC dc = CreateDC(L"WINSPOOL", UTF8ToWide(printer_name).c_str(),
                             NULL, pt_dev_mode.dm_);
           if (!dc) {
             NOTREACHED();

[Peter Kasting, 2012/02/08 00:38:49]

Is it possible for the CreateDC() call to fail legitimately (i.e. in a way we
should handle)?

If so, we should eliminate the NOTREACHED() here.

If not, we should eliminate the entire conditional check and just inline the
CreateDC() call into the Set() call.

[cpu_(ooo_6.6-7.5), 2012/02/10 19:41:55]

Not an expert on printing but I can imagine that if the printer is on the
network this can fail.

             return false;
           }
+          printer_dc_.Set(dc);
+
           hr = E_FAIL;
           DOCINFO di = {0};
           di.cbSize = sizeof(DOCINFO);
           std::wstring doc_name = UTF8ToWide(job_title);
           di.lpszDocName = doc_name.c_str();
           job_id_ = StartDoc(dc, &di);
           if (job_id_ <= 0)
             return false;
 
-          printer_dc_.Set(dc);
           saved_dc_ = SaveDC(printer_dc_.Get());
           print_data_file_path_ = print_data_file_path;
           delegate_ = delegate;
           RenderNextPDFPages();
         } else if (print_data_mime_type == "application/vnd.ms-xpsdocument") {
           bool ret = PrintXPSDocument(printer_name,
                                       job_title,
                                       print_data_file_path,
                                       print_ticket);
           if (ret)
@@ skipping 447 matching lines @@
   RpcStringFree(reinterpret_cast<RPC_WSTR *>(&proxy_id_as_string));
   return ret;
 }
 
 scoped_refptr<PrintSystem> PrintSystem::CreateInstance(
     const base::DictionaryValue* print_system_settings) {
   return new PrintSystemWin;
 }
 
 }  // namespace cloud_print