Refactor print preview web ui

chrome/browser/resources/print_preview/native_layer.js

Index: chrome/browser/resources/print_preview/native_layer.js
diff --git a/chrome/browser/resources/print_preview/native_layer.js b/chrome/browser/resources/print_preview/native_layer.js
new file mode 100644
index 0000000000000000000000000000000000000000..9a017d93dc3ae057c0d4571bdc45289b9fdb67c5
--- /dev/null
+++ b/chrome/browser/resources/print_preview/native_layer.js
@@ -0,0 +1,653 @@
+// 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.
+
+cr.define('print_preview', function() {
+  'use strict';
+
+  /**
+   * An interface to the native Chromium printing system layer.
+   *
+   * @constructor
+   * @extends {cr.EventTarget}
+   */
+  function NativeLayer() {
+    cr.EventTarget.call(this);
+  };
+
+  /**
+   * Events dispatched from the Chromium native layer.
+   * @enum {string}
+   * @const
+   */
+  NativeLayer.Event = {
+    CAPABILITIES_SET: 'print_preview.NativeLayer.CAPABILITIES_SET',
+    CLOUD_PRINT_ENABLE: 'print_preview.NativeLayer.CLOUD_PRINT_ENABLE',
+    DESTINATIONS_RELOAD: 'print_preview.NativeLayer.DESTINATIONS_RELOAD',
+    FILE_SELECTION_CANCEL: 'print_preview.NativeLayer.FILE_SELECTION_CANCEL',
+    FILE_SELECTION_COMPLETE:
+        'print_preview.NativeLayer.FILE_SELECTION_COMPLETE',
+    INITIAL_SETTINGS_SET: 'print_preview.NativeLayer.INITIAL_SETTINGS_SET',
+    LOCAL_DESTINATIONS_SET: 'print_preview.NativeLayer.LOCAL_DESTINATIONS_SET',
+    PAGE_COUNT_CHANGE: 'print_preview.NativeLayer.PAGE_COUNT_CHANGE',
+    PAGE_LAYOUT_CHANGE: 'print_preview.NativeLayer.PAGE_LAYOUT_CHANGE',
+    PAGE_PREVIEW_READY: 'print_preview.NativeLayer.PAGE_PREVIEW_READY',
+    PREVIEW_GENERATION_DONE:
+        'print_preview.NativeLayer.PREVIEW_GENERATION_DONE',
+    PREVIEW_GENERATION_FAIL:
+        'print_preview.NativeLayer.PREVIEW_GENERATION_FAIL',
+    PREVIEW_RELOAD: 'print_preview.NativeLayer.PREVIEW_RELOAD',
+    PRINT_TO_CLOUD: 'print_preview.NativeLayer.PRINT_TO_CLOUD',
+    SETTINGS_INVALID: 'print_preview.NativeLayer.SETTINGS_INVALID'
+  };
+
+  /**
+   * Constant values matching printing::DuplexMode enum.
+   * @enum {number}
+   */
+  NativeLayer.DuplexMode = {
+    SIMPLEX: 0,
+    LONG_EDGE: 1,
+    UNKNOWN_DUPLEX_MODE: -1
+  };
+
+  /**
+   * Enumeration of color modes used by Chromium.
+   * @enum {number}
+   * @private
+   */
+  NativeLayer.ColorMode_ = {
+    GRAY: 1,
+    COLOR: 2
+  };
+
+  /**
+   * Enumeration of the predefined types of page margins. Matches enum
+   * MarginType in printing/print_job_constants.h.
+   * @type {object.<print_preview.Margins.Type, number>}
+   * @private
+   */
+  NativeLayer.MarginsTypeMap_ = {};
+  NativeLayer.MarginsTypeMap_[print_preview.Margins.Type.DEFAULT] = 0;

[dpapad, 2012/04/24 01:24:56]

This mapping was not needed when Margins.Type was an enum of numbers (see
related comment in margins.js). What is the benefit of using strings?

[Robert Toscano, 2012/04/24 22:29:56]

I explain the benefit in my comment response in margins.js.

+  NativeLayer.MarginsTypeMap_[print_preview.Margins.Type.NO_MARGINS] = 1;
+  NativeLayer.MarginsTypeMap_[print_preview.Margins.Type.MINIMUM] = 2;
+  NativeLayer.MarginsTypeMap_[print_preview.Margins.Type.CUSTOM] = 3;
+
+  NativeLayer.prototype = {
+    __proto__: cr.EventTarget.prototype,
+
+    // TODO Remove me
+    dispatchEvent: function(evt) {
+      log(evt.type);
+      cr.EventTarget.prototype.dispatchEvent.call(this, evt);
+    },
+
+    /** Gets the initial settings to initialize the print preview with. */
+    startGetInitialSettings: function() {
+      chrome.send('getInitialSettings');
+    },
+
+    /**
+     * Requests the system's local print destinations. A LOCAL_DESTINATIONS_SET
+     * event will be dispatched in response.
+     */
+    startGetLocalDestinations: function() {
+      chrome.send('getPrinters');
+    },
+
+    /**
+     * Requests the destination's printing capabilities. A CAPABILITIES_SET
+     * event will be dispatched in response.
+     * @param {string} destinationId ID of the destination.
+     */
+    startGetLocalDestinationCapabilities: function(destinationId) {
+      chrome.send('getPrinterCapabilities', [destinationId]);
+    },
+
+    /**
+     * Requests that a preview be generated. The following events may be
+     * dispatched in response:
+     *   - PAGE_COUNT_CHANGE
+     *   - PAGE_LAYOUT_CHANGE
+     *   - PAGE_PREVIEW_READY
+     *   - PREVIEW_GENERATION_DONE
+     *   - PREVIEW_GENERATION_FAIL
+     *   - PREVIEW_RELOAD
+     * @param {print_preview.Destination} destination Destination to print to.
+     * @param {!print_preview.PrintTicketStore} printTicketStore Used to get the
+     *     state of the print ticket.
+     * @param {number} ID of the preview request.
+     */
+    startGetPreview: function(destination, printTicketStore, requestId) {
+      if (!printTicketStore.isTicketValid()) {
+        throw Error('Trying to generate preview when ticket is not valid');
+      }
+
+      var ticket = {
+        'pageRange': [], // TODO this.ticket_.pageRangeSequence,
+        'landscape': printTicketStore.isLandscapeEnabled(),
+        'color': printTicketStore.isColorEnabled() ?
+            NativeLayer.ColorMode_.COLOR : NativeLayer.ColorMode_.GRAY,
+        'headerFooterEnabled': printTicketStore.isHeaderFooterEnabled(),
+        'marginsType': NativeLayer.MarginsTypeMap_[
+            printTicketStore.getMarginsType()],
+        'isFirstRequest': requestId == 0,
+        'requestID': requestId,
+        'previewModifiable': printTicketStore.isDocumentModifiable,
+        'printToPDF': destination != null && destination.isPrintToPdf,
+        'printWithCloudPrint': destination != null && !destination.isLocal,
+        'deviceName': destination == null ? 'foo' : destination.id,
+        'cloudPrintID': destination == null ? 'foo' : destination.id,
+
+        // This field seems to issue a reloadPreviewPages call when true.
+        'generateDraftData': true, // TODO What should this value be?
+
+        // NOTE: Even though the following fields don't directly relate to the
+        // preview, they still need to be included.
+        'duplex': printTicketStore.isDuplexEnabled() ?
+            NativeLayer.DuplexMode.LONG_EDGE : NativeLayer.DuplexMode.SIMPLEX,
+        'copies': printTicketStore.getCopies(),
+        'collate': printTicketStore.isCollateEnabled()
+      };
+
+      if (printTicketStore.getMarginsType() ==
+          print_preview.Margins.Type.CUSTOM) {
+        var customMargins = printTicketStore.getCustomMargins();
+        ticket['marginsCustom'] = {
+          'marginTop': customMargins.top,
+          'marginRight': customMargins.right,
+          'marginBottom': customMargins.bottom,
+          'marginLeft': customMargins.left
+        };
+      }
+
+      var pageCount = requestId == 0 ? -1 : printTicketStore.pageCount;
+      // TODO this.printTicketStore_.getPageNumberSet().size,
+      chrome.send(
+          'getPreview',
+          [JSON.stringify(ticket),
+           pageCount,
+           printTicketStore.isDocumentModifiable]);
+    },
+
+    /**
+     * Persists the selected destination and print ticket for the next print
+     * session.
+     * @param {string} destinatId ID of the destination.
+     * @param {string} serializedTicket Serialized form of the print ticket.
+     */
+    startSaveDestinationAndTicket: function(destinationId, serializedTicket) {
+      chrome.send('saveLastPrinter', [destinationId, serializedTicket]);
+    },
+
+    /**
+     * Requests that the document be printed.
+     * @param {!print_preview.Destination} destination Destination to print to.
+     * @param {!print_preview.PrintTicketStore} printTicketStore Used to get the
+     *     state of the print ticket.
+     * @param {print_preview.CloudPrintInterface} cloudPrintInterface Interface
+     *     to Google Cloud Print.
+     */
+    startPrint: function(destination, printTicketStore, cloudPrintInterface) {
+      if (!printTicketStore.isTicketValid()) {
+        throw Error(
+            'Requesting ticket for preview generator when ticket is not valid');
+      }
+
+      var ticket = {
+        'pageRange': [], // TODO this.ticket_.pageRangeSequence,
+        'landscape': printTicketStore.isLandscapeEnabled(),
+        'color': printTicketStore.isColorEnabled() ?
+            NativeLayer.ColorMode_.COLOR : NativeLayer.ColorMode_.GRAY,
+        'headerFooterEnabled': printTicketStore.isHeaderFooterEnabled(),
+        'marginsType': NativeLayer.MarginsTypeMap_[
+            printTicketStore.getMarginsType()],
+        'generateDraftData': true, // TODO What should this value be?
+        'duplex': printTicketStore.isDuplexEnabled() ?
+            NativeLayer.DuplexMode.LONG_EDGE : NativeLayer.DuplexMode.SIMPLEX,
+        'copies': printTicketStore.getCopies(),
+        'collate': printTicketStore.isCollateEnabled(),
+        'previewModifiable': printTicketStore.isDocumentModifiable,
+        'printToPDF': destination.isPrintToPdf,
+        'printWithCloudPrint': !destination.isLocal,
+        'deviceName': destination.id,
+        'isFirstRequest': false,
+        'requestID': -1
+      };
+
+      if (!destination.isLocal && !destination.isPrintWithCloudPrint) {
+        // We can't set cloudPrintID if the destination is "Print with Cloud
+        // Print" because the native system will try to print to Google Cloud
+        // Print with this ID instead of opening a Google Cloud Print dialog.
+        ticket['cloudPrintID'] = destination.id;
+      }
+
+      if (printTicketStore.getMarginsType() ==
+          print_preview.Margins.Type.CUSTOM) {
+        var customMargins = printTicketStore.getCustomMargins();
+        ticket['marginsCustom'] = {
+          'marginTop': customMargins.top,
+          'marginRight': customMargins.right,
+          'marginBottom': customMargins.bottom,
+          'marginLeft': customMargins.left
+        };
+      }
+
+      var cloudTicket = null;
+      if (!destination.isLocal) {
+        if (!cloudPrintInterface) {
+          throw Error(
+              'Trying to print to a cloud destination but Google Cloud Print ' +
+              'integration is disabled');
+        }
+        cloudTicket = cloudPrintInterface.createPrintTicket(
+            destination, printTicketStore);
+        cloudTicket = JSON.stringify(cloudTicket);
+      }
+
+      chrome.send('print', [JSON.stringify(ticket), cloudTicket]);
+    },
+
+    /** Requests that the current pending print request be cancelled. */
+    startCancelPendingPrint: function() {
+      chrome.send('cancelPendingPrintRequest');
+    },
+
+    /** Shows the system's native printing dialog. */
+    startShowSystemDialog: function() {
+      chrome.send('showSystemDialog');
+    },
+
+    /** Closes the print preview dialog. */
+    startCloseDialog: function() {
+      chrome.send('closePrintPreviewTab');
+      chrome.send('DialogClose');
+    },
+
+    /**
+     * Opens the Google Cloud Print sign-in dialog. The DESTINATIONS_RELOAD
+     * event will be dispatched in response.
+     */
+    startCloudPrintSignIn: function() {
+      chrome.send('signIn');
+    },
+
+    /** Navigates the user to the system printer settings interface. */
+    startManageLocalPrinters: function() {
+      chrome.send('manageLocalPrinters');
+    },
+
+    /** Navigates the user to the Google Cloud Print management page. */
+    startManageCloudPrinters: function() {
+      chrome.send('manageCloudPrinters');
+    }
+  };
+
+  /**
+   * Initial settings retrieved from the native layer.
+   *
+   * @param {boolean} isInKioskAutoPrintMode Whether the print preview should be
+   *     in auto-print mode.
+   * @param {!print_preview.MeasurementSystem} Measurement system of the print
+   *     preview.
+   * @param {boolean} isDocumentModifiable Whether the document to print is
+   *     modifiable.
+   * @param {print_preview.Margins.Type} marginsType Initial margins type.
+   * @param {print_preview.Margins} customMargins Initial custom margins.
+   * @param {boolean} isDuplexEnabled Whether duplexing is initially enabled.
+   * @param {boolean} isHeaderFooterEnabled Whether the header-footer is
+   *     initially enabled.
+   * @param {?string} initialDestinationId ID of the destination to initially
+   *     select.
+   * @constructor
+   */
+  function NativeInitialSettings(
+      isInKioskAutoPrintMode,
+      measurementSystem,
+      isDocumentModifiable,
+      marginsType,
+      customMargins,
+      isDuplexEnabled,
+      isHeaderFooterEnabled,
+      initialDestinationId) {
+
+    /**
+     * Whether the print preview should be in auto-print mode.
+     * @type {boolean}
+     * @private
+     */
+    this.isInKioskAutoPrintMode_ = isInKioskAutoPrintMode;
+
+    /**
+     * Measurement system of the print preview.
+     * @type {!print_preview.MeasurementSystem}
+     * @private
+     */
+    this.measurementSystem_ = measurementSystem;
+
+    /**
+     * Whether the document to print is modifiable.
+     * @type {boolean}
+     * @private
+     */
+    this.isDocumentModifiable_ = isDocumentModifiable;
+
+    /**
+     * Initial margins type.
+     * @type {print_preview.Margins.Type}
+     * @private
+     */
+    this.marginsType_ = marginsType == null ?
+        print_preview.Margins.Type.DEFAULT : marginsType;
+
+    /**
+     * Initial custom margins.
+     * @type {print_preview.Margins}
+     * @private
+     */
+    this.customMargins_ = customMargins;
+
+    /**
+     * Whether duplexing is initially enabled.
+     * @type {boolean}
+     * @private
+     */
+    this.isDuplexEnabled_ = isDuplexEnabled;
+
+    /**
+     * Whether the header-footer is initially enabled.
+     * @type {boolean}
+     * @private
+     */
+    this.isHeaderFooterEnabled_ = isHeaderFooterEnabled;
+
+    /**
+     * ID of the initially selected destination.
+     * @type {?string}
+     * @private
+     */
+    this.initialDestinationId_ = initialDestinationId;
+  };
+
+  NativeInitialSettings.prototype = {
+    /**
+     * @return {boolean} Whether the print preview should be in auto-print mode.
+     */
+    get isInKioskAutoPrintMode() {
+      return this.isInKioskAutoPrintMode_;
+    },
+
+    /**
+     * @return {!print_preview.MeasurementSystem} Measurement system of the
+     *     print preview.
+     */
+    get measurementSystem() {
+      return this.measurementSystem_;
+    },
+
+    /** @return {boolean} Whether the document to print is modifiable. */
+    get isDocumentModifiable() {
+      return this.isDocumentModifiable_;
+    },
+
+    /** @return {print_preview.Margins.Type}  Initial margins type. */
+    get marginsType() {
+      return this.marginsType_;
+    },
+
+    /** @return {print_preview.Margins} Initial custom margins. */
+    get customMargins() {
+      return this.customMargins_;
+    },
+
+    /** @return {boolean} Whether duplexing is initially enabled. */
+    get isDuplexEnabled() {
+      return this.isDuplexEnabled_;
+    },
+
+    /** @return {boolean} Whether the header-footer is initially enabled. */
+    get isHeaderFooterEnabled() {
+      this.isHeaderFooterEnabled_;
+    },
+
+    /** @return {?string} ID of the initially selected destination. */
+    get initialDestinationId() {
+      return this.initialDestinationId_;
+    }
+  };
+
+  return {
+    NativeInitialSettings: NativeInitialSettings,
+    NativeLayer: NativeLayer
+  };
+});
+
+var nativeLayer = new print_preview.NativeLayer();

[dpapad, 2012/04/24 01:24:56]

Global var? Should all global vars be initialized in one place, so that they are
easily spotted?

[Robert Toscano, 2012/04/24 22:29:56]

Yea I'm not sure where I should put them. My goal was to have no global vars,
but because of the way that the native layer calls into javascript, all of the
callbacks below need to work on some global instance. An alternative would be to
set the global vars in the NativeLayer's constructor. Something like:

  print_preview.PrintPreview = function() {
    ...
    this.nativeLayer_ = new print_preview.NativeLayer();
    ...
  };

and then in NativeLayer constructor I would add all of the global functions:

  print_preview.NativeLayer = function() {
    ...
    global['setInitialSettings'] = this.setInitialSettings_.bind(this);
    ...
  };

  print_preview.NativeLayer.prototype = {
    ...
    setInitialSettings_: function(initialSettings) {
      ...
      this.dispatchEvent(event);
    },
    ...
  }

What do you think?

+
+/** @param {object} initialSettings Object containing all initial settings. */
+function setInitialSettings(initialSettings) {
+  // Not using initialSettings['initiatorTabTitle'] since the print preview
+  // no longer opens in a new tab. And because of this,
+  // localStrings.getStringF('printPreviewTitleFormat', initiatorTabTitle)

[dpapad, 2012/04/24 01:24:56]

IIRC, we use the tab title to pre-populate the filename to save in the "Save
File As" dialog when saving to PDF.

[Robert Toscano, 2012/04/24 22:29:56]

This must happen in the native layer then, because all I saw before was that
this method set the print preview's document title to the tab title. The
document's title was never subsequently used in the javascript layer.

+  // is also not used.
+  // TODO Remove those unused local strings.
+
+  // TODO Use initialSettings['cloudPrintData'] somehow. Btw,
+  // initialSettings['cloudPrintData'] is the JSON form of the cloud
+  // printer's capabilities.
+
+  var numberFormatSymbols = print_preview.MeasurementSystem.parseNumberFormat(
+      initialSettings['numberFormat']);
+  var measurementSystem = new print_preview.MeasurementSystem(
+      numberFormatSymbols[0],
+      numberFormatSymbols[1],
+      initialSettings['measurementSystem']);
+
+  var customMargins = null;
+  if (initialSettings.hasOwnProperty('marginTop') &&
+      initialSettings.hasOwnProperty('marginRight') &&
+      initialSettings.hasOwnProperty('marginBottom') &&
+      initialSettings.hasOwnProperty('marginLeft')) {
+    customMargins = new print_preview.Margins(
+        initialSettings['marginTop'] || 0,
+        initialSettings['marginRight'] || 0,
+        initialSettings['marginBottom'] || 0,
+        initialSettings['marginLeft'] || 0);
+  }
+
+  var marginsType;

[dpapad, 2012/04/24 01:24:56]

This also got more complicated by converting MarginsType to an enum of strings,
otherwise it could be a simple assignment, right?

[Robert Toscano, 2012/04/24 22:29:56]

It could be, but then native semantics of these integer values would break
encapsulation, since they would need to be used in the rest of the app (namely
MarginSettings).

+  for (var mt in print_preview.NativeLayer.MarginsTypeMap_) {
+    if (print_preview.NativeLayer.MarginsTypeMap_[mt] ==
+        initialSettings['marginsType']) {
+      marginsType = mt;
+      break;
+    }
+  }
+
+  var nativeInitialSettings = new print_preview.NativeInitialSettings(
+      initialSettings['printAutomaticallyInKioskMode'] || false,
+      measurementSystem,
+      initialSettings['previewModifiable'] || false,
+      marginsType,
+      customMargins,
+      initialSettings['duplex'] || false,
+      initialSettings['headerFooterEnabled'] || false,
+      initialSettings['printerName'] || null);
+
+  var initialSettingsSetEvt =

[dpapad, 2012/04/24 01:24:56]

Nit: An abbreviation for 2 saving characters not really worth it IMO.

[Robert Toscano, 2012/04/24 22:29:56]

Done.

+      new cr.Event(print_preview.NativeLayer.Event.INITIAL_SETTINGS_SET);
+  initialSettingsSetEvt.initialSettings = nativeInitialSettings;
+  nativeLayer.dispatchEvent(initialSettingsSetEvt);
+}
+
+/**
+ * Turn on the integration of Cloud Print.
+ * @param {string} cloudPrintURL The URL to use for cloud print servers.
+ */
+function setUseCloudPrint(cloudPrintURL) {
+  var cloudPrintEnableEvt = new cr.Event(
+      print_preview.NativeLayer.Event.CLOUD_PRINT_ENABLE);
+  cloudPrintEnableEvt.baseCloudPrintUrl = cloudPrintURL;
+  nativeLayer.dispatchEvent(cloudPrintEnableEvt);
+}
+
+/**
+ * Updates the print preview with local printers.
+ * Called from PrintPreviewHandler::SetupPrinterList().
+ * @param {Array} printers Array of printer info objects.
+ */
+function setPrinters(printers) {
+  var localDestsSetEvt = new cr.Event(
+      print_preview.NativeLayer.Event.LOCAL_DESTINATIONS_SET);
+  localDestsSetEvt.destinationInfos = printers;
+  nativeLayer.dispatchEvent(localDestsSetEvt);
+}
+
+/**
+ * Called when native layer gets settings information for a requested local
+ * destination.
+ * @param {Object} settingsInfo printer setting information.
+ */
+function updateWithPrinterCapabilities(settingsInfo) {
+  var capsSetEvt = new cr.Event(
+      print_preview.NativeLayer.Event.CAPABILITIES_SET);
+  capsSetEvt.settingsInfo = settingsInfo;
+  nativeLayer.dispatchEvent(capsSetEvt);
+}
+
+/** Reloads the printer list. */
+function reloadPrintersList() {
+  cr.dispatchSimpleEvent(
+      nativeLayer, print_preview.NativeLayer.Event.DESTINATIONS_RELOAD);
+}
+
+/**
+ * Called from the C++ layer.
+ * Take the PDF data handed to us and submit it to the cloud, closing the print
+ * preview tab once the upload is successful.
+ * @param {string} data Data to send as the print job.
+ */
+function printToCloud(data) {
+  var printToCloudEvt = new cr.Event(
+      print_preview.NativeLayer.Event.PRINT_TO_CLOUD);
+  printToCloudEvt.data = data;
+  nativeLayer.dispatchEvent(printToCloudEvt);
+}
+
+/**
+ * Called from PrintPreviewUI::OnFileSelectionCancelled to notify the print
+ * preview tab regarding the file selection cancel event.
+ */
+function fileSelectionCancelled() {
+  cr.dispatchSimpleEvent(
+      nativeLayer, print_preview.NativeLayer.Event.FILE_SELECTION_CANCEL);
+}
+
+/**
+ * Called from PrintPreviewUI::OnFileSelectionCompleted to notify the print
+ * preview tab regarding the file selection completed event.
+ */
+function fileSelectionCompleted() {
+  // If the file selection is completed and the tab is not already closed it
+  // means that a pending print to pdf request exists.
+  cr.dispatchSimpleEvent(
+      nativeLayer, print_preview.NativeLayer.Event.FILE_SELECTION_COMPLETE);
+}
+
+/**
+ * Display an error message when print preview fails.
+ * Called from PrintPreviewMessageHandler::OnPrintPreviewFailed().
+ */
+function printPreviewFailed() {
+  cr.dispatchSimpleEvent(
+      nativeLayer, print_preview.NativeLayer.Event.PREVIEW_GENERATION_FAIL);
+}
+
+/**
+ * Display an error message when encountered invalid printer settings.
+ * Called from PrintPreviewMessageHandler::OnInvalidPrinterSettings().
+ */
+function invalidPrinterSettings() {
+  cr.dispatchSimpleEvent(
+      nativeLayer, print_preview.NativeLayer.Event.SETTINGS_INVALID);
+}
+
+/**
+ * @param {{contentWidth: number, contentHeight: number, marginLeft: number,
+ *          marginRight: number, marginTop: number, marginBottom: number,
+ *          printableAreaX: number, printableAreaY: number,
+ *          printableAreaWidth: number, printableAreaHeight: number}} pageLayout
+ *          Specifies default page layout details in points.
+ * @param {boolean} hasCustomPageSizeStyle Indicates whether the previewed
+ *     document has a custom page size style.
+ */
+function onDidGetDefaultPageLayout(pageLayout, hasCustomPageSizeStyle) {
+  var pageLayoutChangeEvt = new cr.Event(
+      print_preview.NativeLayer.Event.PAGE_LAYOUT_CHANGE);
+  pageLayoutChangeEvt.pageLayout = pageLayout;
+  pageLayoutChangeEvt.hasCustomPageSizeStyle = hasCustomPageSizeStyle;
+  nativeLayer.dispatchEvent(pageLayoutChangeEvt);
+}
+
+/**
+ * Update the page count and check the page range.
+ * Called from PrintPreviewUI::OnDidGetPreviewPageCount().
+ * @param {number} pageCount The number of pages.
+ * @param {number} previewResponseId The preview request id that resulted in
+ *      this response.
+ */
+function onDidGetPreviewPageCount(pageCount, previewResponseId) {
+  var pageCountChangeEvt = new cr.Event(
+      print_preview.NativeLayer.Event.PAGE_COUNT_CHANGE);
+  pageCountChangeEvt.pageCount = pageCount;
+  pageCountChangeEvt.previewResponseId = previewResponseId;
+  nativeLayer.dispatchEvent(pageCountChangeEvt);
+}
+
+/**
+ * Called when no pipelining previewed pages.
+ * @param {string} previewUid Preview unique identifier.
+ * @param {number} previewResponseId The preview request id that resulted in
+ *     this response.
+ */
+function reloadPreviewPages(previewUid, previewResponseId) {
+  var previewReloadEvt = new cr.Event(
+      print_preview.NativeLayer.Event.PREVIEW_RELOAD);
+  previewReloadEvt.previewUid = previewUid;
+  previewReloadEvt.previewResponseId = previewResponseId;
+  nativeLayer.dispatchEvent(previewReloadEvt);
+}
+
+/**
+ * Notification that a print preview page has been rendered.
+ * Check if the settings have changed and request a regeneration if needed.
+ * Called from PrintPreviewUI::OnDidPreviewPage().
+ * @param {number} pageNumber The page number, 0-based.
+ * @param {string} previewUid Preview unique identifier.
+ * @param {number} previewResponseId The preview request id that resulted in
+ *     this response.
+ */
+function onDidPreviewPage(pageNumber, previewUid, previewResponseId) {
+  var pagePreviewGenEvt = new cr.Event(
+      print_preview.NativeLayer.Event.PAGE_PREVIEW_READY);
+  pagePreviewGenEvt.pageIndex = pageNumber;
+  pagePreviewGenEvt.previewUid = previewUid;
+  pagePreviewGenEvt.previewResponseId = previewResponseId;
+  nativeLayer.dispatchEvent(pagePreviewGenEvt);
+}
+
+/**
+ * Update the print preview when new preview data is available.
+ * Create the PDF plugin as needed.
+ * Called from PrintPreviewUI::PreviewDataIsAvailable().
+ * @param {string} previewUid Preview unique identifier.
+ * @param {number} previewResponseId The preview request id that resulted in
+ *     this response.
+ */
+function updatePrintPreview(previewUid, previewResponseId) {
+  var previewGenDoneEvt = new cr.Event(
+      print_preview.NativeLayer.Event.PREVIEW_GENERATION_DONE);
+  previewGenDoneEvt.previewUid = previewUid;
+  previewGenDoneEvt.previewResponseId = previewResponseId;
+  nativeLayer.dispatchEvent(previewGenDoneEvt);
+}