Print preview page selection should not require a rerendering of draft pages.

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.
 var useCloudPrint = false;
 
 // Store the last selected printer index.
 var lastSelectedPrinterIndex = 0;
 
 // Used to disable some printing options when the preview is not modifiable.
 var previewModifiable = false;
 
 // Destination list special value constants.
 const ADD_CLOUD_PRINTER = 'addCloudPrinter';
 const MANAGE_CLOUD_PRINTERS = 'manageCloudPrinters';
 const MANAGE_LOCAL_PRINTERS = 'manageLocalPrinters';
 const MORE_PRINTERS = 'morePrinters';
 const SIGN_IN = 'signIn';
 const PRINT_TO_PDF = 'Print to PDF';
 
+// State of the print preview settings.
+var printSettings = new PrintSettings();
+
+// Print ready data index.
+const PRINT_READY_DATA_INDEX = -1;
+
 // 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;
 
 // The ID of the initial preview request.
@@ skipping 24 matching lines @@
 var colorSettings;
 
 // True if the user has click 'Advanced...' in order to open the system print
 // dialog.
 var showingSystemDialog = false;
 
 // The range of options in the printer dropdown controlled by cloud print.
 var firstCloudPrintOptionPos = 0;
 var lastCloudPrintOptionPos = firstCloudPrintOptionPos;
 
+// Store the current previewUid.
+var currentPreviewUid = '';
+
+// True if we need to generate draft preview data.
+var generateDraftData = true;
 
 // TODO(abodenha@chromium.org) A lot of cloud print specific logic has
 // made its way into this file.  Refactor to create a cleaner boundary
 // between print preview and GCP code.  Reference bug 88098 when fixing.
 
 // A dictionary of cloud printers that have been added to the printer
 // dropdown.
 var addedCloudPrinters = {};
 
 // The maximum number of cloud printers to allow in the dropdown.
@@ skipping 248 matching lines @@
        'duplex': copiesSettings.duplexMode,
        'copies': copiesSettings.numberOfCopies,
        'collate': copiesSettings.isCollated(),
        'landscape': layoutSettings.isLandscape(),
        'color': colorSettings.isColor(),
        'printToPDF': printToPDF,
        'isFirstRequest' : false,
        'headerFooterEnabled': headerFooterSettings.hasHeaderFooter(),
        'defaultMarginsSelected': marginSettings.isDefaultMarginsSelected(),
        'margins': marginSettings.customMargins,
-       'requestID': -1};
+       'requestID': -1,
+       'generateDraftData': generateDraftData};
 
   var printerList = $('printer-list');
   var selectedPrinter = printerList.selectedIndex;
   if (cloudprint.isCloudPrint(printerList.options[selectedPrinter])) {
     settings['cloudPrintID'] =
         printerList.options[selectedPrinter].value;
   }
   return settings;
 }
 
@@ skipping 56 matching lines @@
     return '';
   return printerList.options[selectedPrinter].value;
 }
 
 /**
  * Asks the browser to print the preview PDF based on current print
  * settings. If the preview is still loading, printPendingFile() will get
  * called once the preview loads.
  */
 function requestToPrintDocument() {
-  hasPendingPrintDocumentRequest = hasPendingPreviewRequest;
+  hasPendingPrintDocumentRequest = hasPendingPrintReadyDocumentRequest;
   var printToPDF = getSelectedPrinterName() == PRINT_TO_PDF;
 
   if (hasPendingPrintDocumentRequest) {
     if (printToPDF) {
       // TODO(thestig) disable controls here.
      } else {
        isTabHidden = true;
        chrome.send('hidePreview');
      }
     return;
@@ skipping 34 matching lines @@
 function sendPrintDocumentRequest() {
   var printerList = $('printer-list');
   var printer = printerList[printerList.selectedIndex];
   chrome.send('saveLastPrinter', [printer.textContent,
                                   cloudprint.getData(printer)]);
   chrome.send('print', [JSON.stringify(getSettings()),
                         cloudprint.getPrintTicketJSON(printer)]);
 }
 
 /**
+ * Loads the selected preview pages.
+ */
+function loadSelectedPages() {
+  hasPendingPreviewRequest = false;
+  pageSettings.updatePageSelection();
+  var pageSet = pageSettings.previouslySelectedPages;
+  var pageCount = pageSet.length;
+  if (pageCount == 0 || currentPreviewUid == '')
+    return;
+
+  for (var i = 0; i < pageCount; i++)
+    onDidPreviewPage(pageSet[i] - 1, currentPreviewUid, lastPreviewRequestID);
+}
+
+/**
  * Asks the browser to generate a preview PDF based on current print settings.
  */
 function requestPrintPreview() {
-  hasPendingPreviewRequest = true;
-  layoutSettings.updateState();
   if (!isTabHidden)
     showLoadingAnimation();
 
-  chrome.send('getPreview', [JSON.stringify(getSettingsWithRequestID())]);
+  if (!hasPendingPreviewRequest && previewModifiable &&
+      hasOnlyPageSettingsChanged()) {
+    loadSelectedPages();
+    generateDraftData = false;
+  } else {
+    hasPendingPreviewRequest = true;
+    generateDraftData = true;
+    pageSettings.updatePageSelection();
+  }
+
+  printSettings.save();
+  layoutSettings.updateState();
+  hasPendingPrintReadyDocumentRequest = true;
+
+  var totalPageCount = pageSettings.totalPageCount;
+  if (!previewModifiable && totalPageCount > 0)
+    generateDraftData = false;
+
+  var pageCount = totalPageCount != undefined ? totalPageCount : -1;
+  chrome.send('getPreview', [JSON.stringify(getSettingsWithRequestID()),
+                             String(pageCount),
+                             previewModifiable]);
 }
 
 /**
  * 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 393 matching lines @@
  *     this response.
  */
 function onDidPreviewPage(pageNumber, previewUid, previewResponseId) {
   if (!isExpectedPreviewResponse(previewResponseId))
     return;
 
   // Refactor
   if (!previewModifiable)
     return;
 
-  var pageIndex = pageSettings.previouslySelectedPages.indexOf(pageNumber + 1);
-
   if (pageSettings.requestPrintPreviewIfNeeded())
     return;
-  if (pageIndex == 0)
-    createPDFPlugin(previewUid);
+
+  var pageIndex = pageSettings.previouslySelectedPages.indexOf(pageNumber + 1);
+  if (pageIndex == -1)
+    return;
+
+  currentPreviewUid = previewUid;
+  if (pageIndex == 0) {
+    createPDFPlugin(pageNumber);
+    hasPendingPreviewRequest = false;
+  }
 
   $('pdf-viewer').loadPreviewPage(
       getPageSrcURL(previewUid, pageNumber), pageIndex);
 }
 
 /**
  * Update the print preview when new preview data is available.
  * Create the PDF plugin as needed.
  * Called from PrintPreviewUI::PreviewDataIsAvailable().
  * @param {boolean} modifiable If the preview is modifiable.
  * @param {string} previewUid Preview unique identifier.
  * @param {number} previewResponseId The preview request id that resulted in
  *     this response.
  */
 function updatePrintPreview(previewUid, previewResponseId) {
   if (!isExpectedPreviewResponse(previewResponseId))
     return;
   hasPendingPreviewRequest = false;
+  hasPendingPrintReadyDocumentRequest = false;
 
   if (!previewModifiable) {
     // If the preview is not modifiable the plugin has not been created yet.
-    createPDFPlugin(previewUid);
+    currentPreviewUid = previewUid;
+    createPDFPlugin(PRINT_READY_DATA_INDEX);
   }
 
   cr.dispatchSimpleEvent(document, 'updatePrintButton');
 
   if (hasPendingPrintDocumentRequest)
     requestToPrintPendingDocument();
 }
 
 /**
+ * Check if only page selection has been changed since the last preview request
+ * and is valid.
+ * @return {boolean} true if the new page selection is valid.
+ */
+function hasOnlyPageSettingsChanged() {
+  var tempPrintSettings = new PrintSettings();
+  tempPrintSettings.save();
+
+  return !!(printSettings.deviceName == tempPrintSettings.deviceName &&
+            printSettings.isLandscape == tempPrintSettings.isLandscape &&
+            printSettings.hasHeaderFooter ==
+                tempPrintSettings.hasHeaderFooter &&
+            pageSettings.hasPageSelectionChangedAndIsValid());
+}
+
+/**
  * Create the PDF plugin or reload the existing one.
- * @param {string} previewUid Preview unique identifier.
+ * @param {number} srcDataIndex Preview data source index.
  */
-function createPDFPlugin(previewUid) {
+function createPDFPlugin(srcDataIndex) {
   var pdfViewer = $('pdf-viewer');
+  var srcURL = getPageSrcURL(currentPreviewUid, srcDataIndex);
   if (pdfViewer) {
     // Need to call this before the reload(), where the plugin resets its
     // internal page count.
     pdfViewer.goToPage('0');
+    pdfViewer.resetPrintPreviewUrl(srcURL);
     pdfViewer.reload();
     pdfViewer.grayscale(!colorSettings.isColor());
     return;
   }
 
-  // Get the complete preview document.
-  var dataIndex = previewModifiable ? '0' : '-1';
-
   pdfViewer = document.createElement('embed');
   pdfViewer.setAttribute('id', 'pdf-viewer');
   pdfViewer.setAttribute('type',
                          'application/x-google-chrome-print-preview-pdf');
-  pdfViewer.setAttribute('src', getPageSrcURL(previewUid, dataIndex));
+  pdfViewer.setAttribute('src', srcURL);
   pdfViewer.setAttribute('aria-live', 'polite');
   pdfViewer.setAttribute('aria-atomic', 'true');
   $('mainview').appendChild(pdfViewer);
   pdfViewer.onload('onPDFLoad()');
   pdfViewer.removePrintButton();
   pdfViewer.grayscale(true);
 }
 
 /**
  * @return {boolean} true if a compatible pdf plugin exists.
  */
 function checkCompatiblePluginExists() {
   var dummyPlugin = $('dummy-viewer')
   return !!(dummyPlugin.onload &&
             dummyPlugin.goToPage &&
             dummyPlugin.removePrintButton &&
             dummyPlugin.loadPreviewPage &&
-            dummyPlugin.printPreviewPageCount);
+            dummyPlugin.printPreviewPageCount &&
+            dummyPlugin.resetPrintPreviewUrl);
 }
 
 window.addEventListener('DOMContentLoaded', onLoad);
 
 /**
  * Sets the default values and sends a request to regenerate preview data.
  * Resets the margin options only if |resetMargins| is true.
  */
 function setDefaultValuesAndRegeneratePreview(resetMargins) {
   if (resetMargins)
     marginSettings.resetMarginsIfNeeded();
   pageSettings.resetState();
   requestPrintPreview();
 }
 
+/**
+ * Class that represents the state of the print settings.
+ */
+function PrintSettings() {
+  this.deviceName = '';
+  this.isLandscape = '';
+  this.hasHeaderFooter = '';
+}
+
+/**
+ *  Takes a snapshot of the print settings.
+ */
+PrintSettings.prototype.save = function() {
+  this.deviceName = getSelectedPrinterName();
+  this.isLandscape = layoutSettings.isLandscape();
+  this.hasHeaderFooter = headerFooterSettings.hasHeaderFooter();
+}
+
 /// Pull in all other scripts in a single shot.
 <include src="print_preview_animations.js"/>
 <include src="print_preview_cloud.js"/>
 <include src="print_preview_utils.js"/>
 <include src="print_header.js"/>
 <include src="page_settings.js"/>
 <include src="copies_settings.js"/>
 <include src="header_footer_settings.js"/>
 <include src="layout_settings.js"/>
 <include src="color_settings.js"/>
 <include src="margin_settings.js"/>