Print Preview: Associating preview requests and responses using an identifier

chrome/browser/resources/print_preview/print_preview.js

 // 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.
 
 // require: cr/ui/print_preview_cloud.js
 
 var localStrings = new LocalStrings();
 
 // If useCloudPrint is true we attempt to connect to cloud print
 // and populate the list of printers with cloud print printers.
@@ skipping 15 matching lines @@
 
 // State of the print preview settings.
 var printSettings = new PrintSettings();
 
 // The name of the default or last used printer.
 var defaultOrLastUsedPrinterName = '';
 
 // True when a pending print preview request exists.
 var hasPendingPreviewRequest = false;
 
+// The ID of the last preview request.
+var lastPreviewRequestID = -1;
+
 // True when a pending print file request exists.
 var hasPendingPrintFileRequest = false;
 
 // True when preview tab is hidden.
 var isTabHidden = false;
 
 // Object holding all the pages related settings.
 var pageSettings;
 
 // Object holding all the copies related settings.
@@ skipping 288 matching lines @@
  * @return {number} duplex mode.
  */
 function getDuplexMode() {
   // Constants values matches printing::DuplexMode enum.
   const SIMPLEX = 0;
   const LONG_EDGE = 1;
   return !copiesSettings.twoSidedCheckbox.checked ? SIMPLEX : LONG_EDGE;
 }
 
 /**
- * Creates a JSON string based on the values in the printer settings.
+ * Creates an object based on the values in the printer settings.
  *
- * @return {string} JSON string with print job settings.
+ * @return {Object} Object containing print job settings.
  */
-function getSettingsJSON() {
+function getSettings() {
   var deviceName = getSelectedPrinterName();
   var printToPDF = (deviceName == PRINT_TO_PDF);
 
-  var settings = {'deviceName': deviceName,
-                  'pageRange': pageSettings.selectedPageRanges,
-                  'printAll': pageSettings.allPagesRadioButton.checked,
-                  'duplex': getDuplexMode(),
-                  'copies': copiesSettings.numberOfCopies,
-                  'collate': isCollated(),
-                  'landscape': isLandscape(),
-                  'color': isColor(),
-                  'printToPDF': printToPDF};
+  var settings =
+      {'deviceName': deviceName,
+       'pageRange': pageSettings.selectedPageRanges,
+       'printAll': pageSettings.allPagesRadioButton.checked,
+       'duplex': getDuplexMode(),
+       'copies': copiesSettings.numberOfCopies,
+       'collate': isCollated(),
+       'landscape': isLandscape(),
+       'color': isColor(),
+       'printToPDF': printToPDF,
+       'requestID': 0};
+
   var printerList = $('printer-list');
   var selectedPrinter = printerList.selectedIndex;
   if (cloudprint.isCloudPrint(printerList.options[selectedPrinter])) {
     settings['cloudPrintID'] =
         printerList.options[selectedPrinter].value;
   }
-
-  return JSON.stringify(settings);
+  return settings;
 }
 
 /**
+ * @return {number} The next unused preview request id.
+ */
+function generatePreviewRequestID() {
+  return ++lastPreviewRequestID;
+}
+
+/**
  * Returns the name of the selected printer or the empty string if no
  * printer is selected.
  * @return {string} The name of the currently selected printer.
  */
 function getSelectedPrinterName() {
   var printerList = $('printer-list')
   var selectedPrinter = printerList.selectedIndex;
   if (selectedPrinter < 0)
     return '';
   return printerList.options[selectedPrinter].value;
@@ skipping 52 matching lines @@
 }
 
 /**
  * Sends a message to initiate print workflow.
  */
 function sendPrintFileRequest() {
   var printerList = $('printer-list');
   var printer = printerList[printerList.selectedIndex];
   chrome.send('saveLastPrinter', [printer.textContent,
                                   cloudprint.getData(printer)]);
-  chrome.send('print', [getSettingsJSON(),
+  chrome.send('print', [JSON.stringify(getSettings()),
                         cloudprint.getPrintTicketJSON(printer)]);
 }
 
 /**
  * Asks the browser to generate a preview PDF based on current print settings.
  */
 function requestPrintPreview() {
   hasPendingPreviewRequest = true;
   removeEventListeners();
   printSettings.save();
   if (!isTabHidden)
     showLoadingAnimation();
 
-  chrome.send('getPreview', [getSettingsJSON()]);
+  var settings = getSettings();
+  settings.requestID = generatePreviewRequestID();
+  chrome.send('getPreview', [JSON.stringify(settings)]);
 }
 
 /**
  * Called from PrintPreviewUI::OnFileSelectionCancelled to notify the print
  * preview tab regarding the file selection cancel event.
  */
 function fileSelectionCancelled() {
   // TODO(thestig) re-enable controls here.
 }
 
@@ skipping 324 matching lines @@
   // TODO(thestig) Make use of |pageNumber| for pipelined preview generation.
 }
 
 /**
  * Update the print preview when new preview data is available.
  * Create the PDF plugin as needed.
  * Called from PrintPreviewUI::PreviewDataIsAvailable().
  * @param {string} jobTitle The print job title.
  * @param {boolean} modifiable If the preview is modifiable.
  * @param {string} previewUid Preview unique identifier.
+ * @param {number} previewRequestId The preview request id that resulted in this
+ *     response.
  */
-function updatePrintPreview(jobTitle, modifiable, previewUid) {
+function updatePrintPreview(jobTitle,
+                            modifiable,
+                            previewUid,
+                            previewRequestId) {
+  if (lastPreviewRequestID != previewRequestId)
+    return;
   hasPendingPreviewRequest = false;
 
   if (checkIfSettingsChangedAndRegeneratePreview())
     return;
 
   previewModifiable = modifiable;
   document.title = localStrings.getStringF('printPreviewTitleFormat', jobTitle);
 
   createPDFPlugin(previewUid);
   updatePrintSummary();
@@ skipping 168 matching lines @@
 }
 
 /**
  * Takes a snapshot of the print settings.
  */
 PrintSettings.prototype.save = function() {
   this.deviceName = getSelectedPrinterName();
   this.isLandscape = isLandscape();
 }