Print Preview: Hook up the print button to initiate printing without displaying a print dialog.

chrome/browser/ui/webui/print_preview_handler.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 "chrome/browser/ui/webui/print_preview_handler.h"
 
+#include "base/json/json_reader.h"
 #include "base/values.h"
 #include "chrome/browser/renderer_host/render_view_host.h"
 #include "printing/backend/print_backend.h"
 
 PrintPreviewHandler::PrintPreviewHandler()
     : print_backend_(printing::PrintBackend::CreateInstance(NULL)) {
 }
 
 PrintPreviewHandler::~PrintPreviewHandler() {
 }
@@ skipping 11 matching lines @@
   printing::PrinterList printer_list;
   print_backend_->EnumeratePrinters(&printer_list);
   for (printing::PrinterList::iterator index = printer_list.begin();
        index != printer_list.end(); ++index) {
     printers.Append(new StringValue(index->printer_name));
   }
 
   web_ui_->CallJavascriptFunction(L"setPrinters", printers);
 }
 
-void PrintPreviewHandler::HandlePrint(const ListValue*) {
-  web_ui_->GetRenderViewHost()->PrintForPrintPreview();
+void PrintPreviewHandler::HandlePrint(const ListValue* args) {
+  std::string json_str;
+  CHECK(args->GetString(0, &json_str)) << "Could not read JSON argument";

[Lei Zhang, 2011/03/02 23:28:54]

I would not do a CHECK here. This would imply if the renderer process send us a
bad message, then the browser process would crash! Same for the CHECKs below.
You should not be sprinkling CHECKs in your code so liberally.

[kmadhusu, 2011/03/04 19:39:02]

Fixed.

+  if (json_str.empty()) {
+    NOTREACHED() << "Empty print job settings";
+    return;
+  }
+  scoped_ptr<DictionaryValue> settings(static_cast<DictionaryValue*>(
+          base::JSONReader::Read(json_str, false)));
+  CHECK(settings.get() && settings->IsType(Value::TYPE_DICTIONARY))
+      << "Print job settings must be a dictionary.";
+
+  CHECK(!settings->empty()) << "Print job settings dictionary is empty";
+  web_ui_->GetRenderViewHost()->PrintForPrintPreview(*settings);
 }