Print Preview: Get the default printer and send a preview request, so print preview generation and printer enumeration can happen in parallel.

BUG=84126
TEST=none
Review URL: http://codereview.chromium.org/7084015

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@87189 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 76 insertions, 3 deletions

diff --git a/chrome/browser/resources/print_preview.js b/chrome/browser/resources/print_preview.js
index 29297d1..c37fc14b 100644
--- a/chrome/browser/resources/print_preview.js
+++ b/chrome/browser/resources/print_preview.js
@@ -49,7 +49,7 @@ function onLoad() {
   $('print-button').disabled = true;
   $('controls').onsubmit = function() { return false; };
   $('dancing-dots').classList.remove('invisible');
-  chrome.send('getPrinters');
+  chrome.send('getDefaultPrinter');
 }
 
 /**
@@ -362,6 +362,20 @@ function requestPrintPreview() {
 }
 
 /**
+ * Set the default printer. If there is one, generate a print preview.
+ * @param {string} Name of the default printer. Empty if none.
+ */
+function setDefaultPrinter(printer) {
+  // Add a placeholder value so the printer list looks valid.
+  addDestinationListOption('', '', true, true);
+  if (printer) {
+    $('printer-list')[0].value = printer;
+    updateControlsWithSelectedPrinterCapabilities();
+  }
+  chrome.send('getPrinters');
+}
+
+/**
  * Fill the printer list drop down.
  * Called from PrintPreviewHandler::SendPrinterList().
  * @param {Array} printers Array of printer info objects.
@@ -369,11 +383,24 @@ function requestPrintPreview() {
  */
 function setPrinters(printers, defaultPrinterIndex) {
   var printerList = $('printer-list');
+  // If there exists a dummy printer value, then setDefaultPrinter() already
+  // requested a preview, so no need to do it again.
+  var needPreview = (printerList[0].value == '');
   for (var i = 0; i < printers.length; ++i) {
+    // Check if we are looking at the default printer.
+    if (i == defaultPrinterIndex) {
+      // If the default printer from setDefaultPrinter() does not match the
+      // enumerated value, (re)generate the print preview.
+      if (printers[i].deviceName != printerList[0].value)
+        needPreview = true;
+    }
     addDestinationListOption(printers[i].printerName, printers[i].deviceName,
                              i == defaultPrinterIndex, false);
   }
 
+  // Remove the dummy printer added in setDefaultPrinter().
+  printerList.remove(0);
+
   if (printers.length != 0)
     addDestinationListOption('', '', false, true);
 
@@ -387,7 +414,9 @@ function setPrinters(printers, defaultPrinterIndex) {
                            MANAGE_PRINTERS, false, false);
 
   printerList.disabled = false;
-  updateControlsWithSelectedPrinterCapabilities();
+
+  if (needPreview)
+    updateControlsWithSelectedPrinterCapabilities();
 }
 
 /**
diff --git a/chrome/browser/ui/webui/print_preview_handler.cc b/chrome/browser/ui/webui/print_preview_handler.cc
index 284c05a..9587234 100644
--- a/chrome/browser/ui/webui/print_preview_handler.cc
+++ b/chrome/browser/ui/webui/print_preview_handler.cc
@@ -162,6 +162,25 @@ class PrintSystemTaskProxy
         has_logged_printers_count_(has_logged_printers_count) {
   }
 
+  void GetDefaultPrinter() {
+    VLOG(1) << "Get default printer start";
+    StringValue* default_printer =
+        new StringValue(print_backend_->GetDefaultPrinterName());
+    VLOG(1) << "Get default printer finished, found: " << default_printer;
+
+    BrowserThread::PostTask(
+        BrowserThread::UI, FROM_HERE,
+        NewRunnableMethod(this,
+                          &PrintSystemTaskProxy::SendDefaultPrinter,
+                          default_printer));
+  }
+
+  void SendDefaultPrinter(StringValue* default_printer) {
+    if (handler_)
+      handler_->SendDefaultPrinter(*default_printer);
+    delete default_printer;
+  }
+
   void EnumeratePrinters() {
     VLOG(1) << "Enumerate printers start";
     ListValue* printers = new ListValue;
@@ -329,6 +348,8 @@ PrintPreviewHandler::~PrintPreviewHandler() {
 }
 
 void PrintPreviewHandler::RegisterMessages() {
+  web_ui_->RegisterMessageCallback("getDefaultPrinter",
+      NewCallback(this, &PrintPreviewHandler::HandleGetDefaultPrinter));
   web_ui_->RegisterMessageCallback("getPrinters",
       NewCallback(this, &PrintPreviewHandler::HandleGetPrinters));
   web_ui_->RegisterMessageCallback("getPreview",
@@ -349,6 +370,17 @@ TabContents* PrintPreviewHandler::preview_tab() {
   return web_ui_->tab_contents();
 }
 
+void PrintPreviewHandler::HandleGetDefaultPrinter(const ListValue*) {
+  scoped_refptr<PrintSystemTaskProxy> task =
+      new PrintSystemTaskProxy(AsWeakPtr(),
+                               print_backend_.get(),
+                               has_logged_printers_count_);
+  BrowserThread::PostTask(
+      BrowserThread::FILE, FROM_HERE,
+      NewRunnableMethod(task.get(),
+                        &PrintSystemTaskProxy::GetDefaultPrinter));
+}
+
 void PrintPreviewHandler::HandleGetPrinters(const ListValue*) {
   scoped_refptr<PrintSystemTaskProxy> task =
       new PrintSystemTaskProxy(AsWeakPtr(),
@@ -522,6 +554,11 @@ void PrintPreviewHandler::SendPrinterCapabilities(
                                   settings_info);
 }
 
+void PrintPreviewHandler::SendDefaultPrinter(
+    const StringValue& default_printer) {
+  web_ui_->CallJavascriptFunction("setDefaultPrinter", default_printer);
+}
+
 void PrintPreviewHandler::SendPrinterList(
     const ListValue& printers,
     const FundamentalValue& default_printer_index) {
diff --git a/chrome/browser/ui/webui/print_preview_handler.h b/chrome/browser/ui/webui/print_preview_handler.h
index f5f2a6a..72fdfbd 100644
--- a/chrome/browser/ui/webui/print_preview_handler.h
+++ b/chrome/browser/ui/webui/print_preview_handler.h
@@ -12,8 +12,9 @@
 #include "content/browser/webui/web_ui.h"
 
 class FilePath;
-class PrintSystemTaskProxy;
 class FundamentalValue;
+class PrintSystemTaskProxy;
+class StringValue;
 
 namespace printing {
 class PrintBackend;
@@ -41,6 +42,9 @@ class PrintPreviewHandler : public WebUIMessageHandler,
 
   TabContents* preview_tab();
 
+  // Get the default printer. |args| is unused.
+  void HandleGetDefaultPrinter(const ListValue* args);
+
   // Get the list of printers. |args| is unused.
   void HandleGetPrinters(const ListValue* args);
 
@@ -72,6 +76,9 @@ class PrintPreviewHandler : public WebUIMessageHandler,
   // |settings_info| contains printer capabilities information.
   void SendPrinterCapabilities(const DictionaryValue& settings_info);
 
+  // Send the default printer to the Web UI.
+  void SendDefaultPrinter(const StringValue& default_printer);
+
   // Send the list of printers to the Web UI.
   void SendPrinterList(const ListValue& printers,
                        const FundamentalValue& default_printer_index);