Refactor print preview web ui

chrome/browser/resources/print_preview/preview_generator.js

+// 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';
+
+  // TODO Need to handle termination case--detach event listeners from native
+  // layer.
+
+  /**
+   * Interface to the Chromium print preview generator.
+   *
+   * @param {!print_preview.DestinationStore} destinationStore Used to get the
+   *     currently selected destination.
+   * @param {!print_preview.PrintTicketStore} printTicketStore Used to read the
+   *     state of the ticket and write document information.
+   * @param {!print_preview.NativeLayer} nativeLayer Used to communicate to
+   *     Chromium's preview rendering system.
+   * @constructor
+   * @extends {cr.EventTarget}
+   */
+  function PreviewGenerator(destinationStore, printTicketStore, nativeLayer) {
+    cr.EventTarget.call(this);
+
+    /**
+     * Used to get the currently selected destination.
+     * @type {!print_preview.DestinationStore}
+     * @private
+     */
+    this.destinationStore_ = destinationStore;
+
+    /**
+     * Used to read the state of the ticket and write document information.
+     * @type {!print_preview.PrintTicketStore}
+     * @private
+     */
+    this.printTicketStore_ = printTicketStore;
+
+    /**
+     * Interface to the Chromium native layer.
+     * @type {!print_preview.NativeLayer}
+     * @private
+     */
+    this.nativeLayer_ = nativeLayer;
+
+    /**
+     * ID of current in-flight request. Requests that do not share this ID will
+     * be ignored.
+     * @type {number}
+     * @private
+     */
+    this.inFlightRequestId_ = -1;
+
+    /**
+     * Whether the previews are being generated in landscape mode.
+     * @type {boolean}
+     * @private
+     */
+    this.isLandscapeEnabled_ = false;
+
+    /**
+     * Whether the previews are being generated with a header and footer.
+     * @type {boolean}
+     * @private
+     */
+    this.isHeaderFooterEnabled_ = false;
+
+    /**
+     * Whether the previews are being generated in color.
+     * @type {boolean}
+     * @private
+     */
+    this.isColorEnabled_ = false;
+
+    /**
+     * Page number set used to generate the last preview.
+     * @type {print_preview.PageNumberSet}
+     * @private
+     */
+    this.pageNumberSet_ = null;
+
+    /**
+     * Margins type used to generate the last preview.
+     * @type {print_preview.Margins.Type}
+     * @private
+     */
+    this.marginsType_ = print_preview.Margins.Type.DEFAULT;
+
+    /**
+     * Custom margins used to generate the last preview.
+     * @type {print_preview.Margins}
+     * @private
+     */
+    this.customMargins_ = null;
+
+    /**
+     * Event tracker used to keep track of native layer events.
+     * @type {!EventTracker}
+     * @private
+     */
+    this.tracker_ = new EventTracker();
+
+    this.addEventListeners_();
+  };
+
+  /**
+   * Events dispatched by the preview generator.
+   * @enum {string}
+   */
+  PreviewGenerator.Event = {
+    // Dispatched when the document can be printed.
+    DOCUMENT_READY: 'print_preview.PreviewGenerator.DOCUMENT_READY',
+
+    // Dispatched when a page preview is ready. The previewIndex field of the
+    // event is the index of the page in the modified document, not the
+    // original. So page 4 of the original document might be previewIndex = 0 of
+    // the modified document.
+    PAGE_READY: 'print_preview.PreviewGenerator.PAGE_READY',
+
+    // Dispatched when the current print preview request fails.
+    FAIL: 'print_preview.PreviewGenerator.FAIL'
+  };
+
+  PreviewGenerator.prototype = {
+    __proto__: cr.EventTarget.prototype,
+
+    /** @override */
+    dispatchEvent: function(evt) {
+      // TODO REMOVE ME
+      log(evt.type);
+      cr.EventTarget.prototype.dispatchEvent.call(this, evt);
+    },
+
+    /**
+     * Request that new preview be generated. A preview request will not be
+     * generated if the print ticket has not changed sufficiently.
+     */
+    requestPreview: function() {
+      if (this.hasPreviewChanged_()) {
+        log('print_preview.PreviewGenerator.requestPreview');
+        this.isLandscapeEnabled_ = this.printTicketStore_.isLandscapeEnabled();
+        this.isHeaderFooterEnabled_ =
+            this.printTicketStore_.isHeaderFooterEnabled();
+        this.isColorEnabled_ = this.printTicketStore_.isColorEnabled();
+        this.pageNumberSet_ = this.printTicketStore_.getPageNumberSet();
+        this.marginsType_ = this.printTicketStore_.getMarginsType();
+        this.customMargins_ = this.printTicketStore_.getCustomMargins();
+
+        this.inFlightRequestId_++;
+        this.nativeLayer_.startGetPreview(
+            this.destinationStore_.selectedDestination,
+            this.printTicketStore_,
+            this.inFlightRequestId_);
+      }
+    },
+
+    /** Removes all event listeners that the preview generator has attached. */
+    removeEventListeners: function() {
+      this.tracker_.removeAll();
+    },
+
+    /**
+     * Adds event listeners to the relevant native layer events.
+     * @private
+     */
+    addEventListeners_: function() {
+      this.tracker_.add(
+          this.nativeLayer_,
+          print_preview.NativeLayer.Event.PAGE_LAYOUT_CHANGE,
+          this.onPageLayoutChange_.bind(this));
+      this.tracker_.add(
+          this.nativeLayer_,
+          print_preview.NativeLayer.Event.PAGE_COUNT_CHANGE,
+          this.onPageCountChange_.bind(this));
+      this.tracker_.add(
+          this.nativeLayer_,
+          print_preview.NativeLayer.Event.PREVIEW_RELOAD,
+          this.onPreviewReload_.bind(this));
+      this.tracker_.add(
+          this.nativeLayer_,
+          print_preview.NativeLayer.Event.PAGE_PREVIEW_READY,
+          this.onPagePreviewReady_.bind(this));
+      this.tracker_.add(
+          this.nativeLayer_,
+          print_preview.NativeLayer.Event.PREVIEW_GENERATION_DONE,
+          this.onPreviewGenerationDone_.bind(this));
+      this.tracker_.add(
+          this.nativeLayer_,
+          print_preview.NativeLayer.Event.PREVIEW_GENERATION_FAIL,
+          this.onPreviewGenerationFail_.bind(this));
+    },
+
+    /**
+     * Dispatches a PAGE_READY event to signal that a page preview is ready.
+     * @param {number} previewIndex Index of the page with respect to the pages
+     *     shown in the preview. E.g an index of 0 might be the fifth page in

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

Took me a while to parse this comment. I think it would be slightly more clear
as follows
"An index of 0 is the first displayed page but not the first original document
page necessarily."

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

Done.

+     *     in the document, but it will be the first page to be shown in the
+     *     preview.
+     * @param {number} pageNumber Number of the page with respect to the
+     *     document. A value of 3 means it's the third page of the document.
+     * @param {string} previewUid Unique identifier of the preview.
+     * @private
+     */
+    dispatchPageReadyEvent_: function(previewIndex, pageNumber, previewUid) {
+      var pageGenEvt = new cr.Event(PreviewGenerator.Event.PAGE_READY);
+      pageGenEvt.previewIndex = previewIndex;
+      pageGenEvt.previewUrl =
+          'chrome://print/' + previewUid + '/' + (pageNumber - 1) +
+          '/print.pdf';
+      this.dispatchEvent(pageGenEvt);
+    },
+
+    /**
+     * Called when the page layout of the document has changed. Always occurs
+     * as a result of a preview request.
+     * @param {cr.Event} evt Contains layout info about the document.
+     * @private
+     */
+    onPageLayoutChange_: function(evt) {
+      // NOTE: A request ID is not specified, so assuming its for the current
+      // in-flight request.
+
+      // TODO Do we need this?
+      //var hasCustomPageSizeStyle = evt.hasCustomPageSizeStyle;
+
+      // Printable area info is unavailable on linux nor Google Chrome OS.
+      // TODO Maybe we can not have to have this if condition, and always set
+      // printable area?
+      log(JSON.stringify(evt.pageLayout));
+      if (!cr.isLinux && !cr.isChromeOS) {
+        var origin = new print_preview.Coordinate2d(
+            evt.pageLayout.printableAreaX,
+            evt.pageLayout.printableAreaY);
+        var size = new print_preview.Size(
+            evt.pageLayout.printableAreaWidth,
+            evt.pageLayout.printableAreaHeight);
+        this.printTicketStore_.updatePrintableArea(
+            new print_preview.PrintableArea(origin, size));
+      } // TODO else create a default printable area?
+
+      var margins = new print_preview.Margins(
+          evt.pageLayout.marginTop,
+          evt.pageLayout.marginRight,
+          evt.pageLayout.marginBottom,
+          evt.pageLayout.marginLeft);
+      if (this.printTicketStore_.hasMarginsCapability()) {
+        this.printTicketStore_.updateCustomMargins(margins);
+      }
+
+      var pageSize = new print_preview.Size(
+          evt.pageLayout.contentWidth + margins.left + margins.right,
+          evt.pageLayout.contentHeight + margins.top + margins.bottom);
+      this.printTicketStore_.updatePageSize(pageSize);
+    },
+
+    /**
+     * Called when the document page count is received from the native layer.
+     * Always occurs as a result of a preview request.
+     * @param {cr.Event} evt Contains the document's page count.
+     * @private
+     */
+    onPageCountChange_: function(evt) {
+      if (this.inFlightRequestId_ != evt.previewResponseId) {
+        return; // Ignore old response.
+      }
+      this.printTicketStore_.updatePageCount(evt.pageCount);
+    },
+
+    /**
+     * Called when the print preview should be reloaded.
+     * @param {cr.Event} evt Contains the preview UID and request ID.
+     * @private
+     */
+    onPreviewReload_: function(evt) {
+      if (this.inFlightRequestId_ != evt.previewResponseId) {
+        return; // Ignore old response.
+      }
+      var pageNumberSet = this.printTicketStore_.getPageNumberSet();
+      for (var i = 0; i < pageNumberSet.size; i++) {
+        var pageNumber = pageNumberSet.getPageNumberAt(i);
+        this.dispatchPageReadyEvent_(i, pageNumber, evt.previewUid);
+      }
+    },
+
+    /**
+     * Called when a page's preview has been generated. Dispatches a
+     * PAGE_READY event.
+     * @param {cr.Event} evt Contains the page index and preview UID.
+     * @private
+     */
+    onPagePreviewReady_: function(evt) {
+      if (this.inFlightRequestId_ != evt.previewResponseId) {
+        return; // Ignore old response.
+      }
+      var pageNumber = evt.pageIndex + 1;
+      if (this.printTicketStore_.getPageNumberSet().hasPageNumber(pageNumber)) {
+        var previewIndex = this.printTicketStore_.getPageNumberSet()
+            .getPageNumberIndex(pageNumber);
+        this.dispatchPageReadyEvent_(previewIndex, pageNumber, evt.previewUid);
+      }
+    },
+
+    /**
+     * Called when the preview generation is complete. Dispatches a
+     * DOCUMENT_READY event.
+     * @param {cr.Event} evt Contains the preview UID and response ID.
+     * @private
+     */
+    onPreviewGenerationDone_: function(evt) {
+      if (this.inFlightRequestId_ != evt.previewResponseId) {
+        return; // Ignore old response.
+      }
+    },
+
+    /**
+     * Called when the preview generation fails.
+     * @private
+     */
+    onPreviewGenerationFail_: function() {
+      // NOTE: No request ID is returned from Chromium so its assumed its the
+      // current one.
+      cr.dispatchSimpleEvent(this, PreviewGenerator.Event.FAIL);
+    },
+
+    /**
+     * @return {boolean} Whether the print ticket has changed sufficiently to
+     *     determine whether a new preview request should be issued.
+     * @private
+     */
+    hasPreviewChanged_: function() {
+      var ticketStore = this.printTicketStore_;
+      return this.inFlightRequestId_ == -1 ||
+          ticketStore.isLandscapeEnabled() != this.isLandscapeEnabled_ ||
+          ticketStore.isHeaderFooterEnabled() != this.isHeaderFooterEnabled_ ||
+          ticketStore.isColorEnabled() != this.isColorEnabled_ ||
+          !ticketStore.getPageNumberSet().equals(this.pageNumberSet_) ||
+          ticketStore.getMarginsType() != this.marginsType_ ||
+          (this.marginsType_ == print_preview.Margins.Type.CUSTOM &&
+              !ticketStore.getCustomMargins().equals(this.customMargins_));
+    }
+  };
+
+  // Export
+  return {
+    PreviewGenerator: PreviewGenerator
+  };
+});