Print Preview: Keep the cancel button enabled whenever possible. Hook up the escape key to cancel.

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 35 matching lines @@
 
 // True when a pending print file request exists.
 var hasPendingPrintDocumentRequest = false;
 
 // True when the complete metafile for the previewed doc is ready.
 var isPrintReadyMetafileReady = false;
 
 // True when preview tab is hidden.
 var isTabHidden = false;
 
+// Object holding the print and cancel buttons.
+var printHeader;
+
 // Object holding all the pages related settings.
 var pageSettings;
 
 // Object holding all the copies related settings.
 var copiesSettings;
 
 // Object holding all the layout related settings.
 var layoutSettings;
 
 // Object holding all the margin related settings.
@@ skipping 31 matching lines @@
 
 /**
  * Window onload handler, sets up the page and starts print preview by getting
  * the printer list.
  */
 function onLoad() {
   cr.enablePlatformSpecificCSSRules();
   initialPreviewRequestID = randomInteger(MIN_REQUEST_ID, MAX_REQUEST_ID);
   lastPreviewRequestID = initialPreviewRequestID;
 
+  printHeader = print_preview.PrintHeader.getInstance();
+  printHeader.addEventListeners();
+
   if (!checkCompatiblePluginExists()) {
     disableInputElementsInSidebar();
     displayErrorMessageWithButton(localStrings.getString('noPlugin'),
                                   localStrings.getString('launchNativeDialog'),
                                   launchNativePrintDialog);
     $('mainview').parentElement.removeChild($('dummy-viewer'));
     return;
   }
 
   $('system-dialog-link').addEventListener('click', onSystemDialogLinkClicked);
   $('mainview').parentElement.removeChild($('dummy-viewer'));
 
   $('printer-list').disabled = true;
 
-  printHeader = print_preview.PrintHeader.getInstance();
   pageSettings = print_preview.PageSettings.getInstance();
   copiesSettings = print_preview.CopiesSettings.getInstance();
   layoutSettings = print_preview.LayoutSettings.getInstance();
   marginSettings = print_preview.MarginSettings.getInstance();
   headerFooterSettings = print_preview.HeaderFooterSettings.getInstance();
   colorSettings = print_preview.ColorSettings.getInstance();
-  printHeader.addEventListeners();
   pageSettings.addEventListeners();
   copiesSettings.addEventListeners();
   headerFooterSettings.addEventListeners();
   layoutSettings.addEventListeners();
   marginSettings.addEventListeners();
   colorSettings.addEventListeners();
   $('printer-list').onchange = updateControlsWithSelectedPrinterCapabilities;
 
   showLoadingAnimation();
   chrome.send('getInitiatorTabTitle');
   chrome.send('getDefaultPrinter');
 }
 
 /**
  * Disables the input elements in the sidebar.
  */
 function disableInputElementsInSidebar() {
   var els = $('sidebar').querySelectorAll('input, button, select');
-  for (var i = 0; i < els.length; i++)
+  for (var i = 0; i < els.length; i++) {
+    if (els[i] == printHeader.cancelButton)
+      continue;
     els[i].disabled = true;
+  }
 }
 
 /**
  * Disables the controls in the sidebar, shows the throbber and instructs the
  * backend to open the native print dialog.
  */
 function onSystemDialogLinkClicked() {
   if (showingSystemDialog)
     return;
   showingSystemDialog = true;
   disableInputElementsInSidebar();
   $('system-dialog-throbber').classList.remove('hidden');
   chrome.send('showSystemDialog');
 }
 
 /**
  * Similar to onSystemDialogLinkClicked(), but specific to the
  * 'Launch native print dialog' UI.
  */
 function launchNativePrintDialog() {
   if (showingSystemDialog)
     return;
   showingSystemDialog = true;
   $('error-button').disabled = true;
+  cr.dispatchSimpleEvent(document, 'disableCancelButton');
   $('native-print-dialog-throbber').classList.remove('hidden');
   chrome.send('showSystemDialog');
 }
 
 /**
  * Disables the controls which need the initiator tab to generate preview
  * data. This function is called when the initiator tab has crashed.
  * @param {string} initiatorTabURL The URL of the initiator tab.
  */
 function onInitiatorTabCrashed(initiatorTabURL) {
@@ skipping 702 matching lines @@
     hasPendingPreviewRequest = false;
     createPDFPlugin(PRINT_READY_DATA_INDEX);
   }
 
   cr.dispatchSimpleEvent(document, 'updatePrintButton');
   if (previewModifiable)
     sendPrintDocumentRequestIfNeeded();
 }
 
 /**
- * Checks to see if the requested print data is available for printing  and
+ * Checks to see if the requested print data is available for printing and
  * sends a print document request if needed.
  */
 function sendPrintDocumentRequestIfNeeded() {
   if (!hasPendingPrintDocumentRequest || !isFirstPageLoaded)
     return;
 
   // If the selected printer is PRINT_TO_PDF or PRINT_WITH_CLOUD_PRINT or
   // the preview source is not modifiable, we need the print ready data for
   // printing. If the preview source is modifiable, we need to wait till all
   // the requested pages are loaded in the plugin for printing.
@@ skipping 109 matching lines @@
  * 'getInitiatorTabTitle' message.
  * @param {string} initiatorTabTitle The title of the initiator tab.
  */
 function setInitiatorTabTitle(initiatorTabTitle) {
   if (initiatorTabTitle == '')
     return;
   document.title = localStrings.getStringF(
       'printPreviewTitleFormat', initiatorTabTitle);
 }
 
+/**
+ * Closes this print preview tab.
+ */
+function closePrintPreviewTab() {
+  chrome.send('closePrintPreviewTab');
+}
+
+/**
+  * Handle keyboard events.
+  * @param {Event} e The keyboard event.
+  */
+function onKeyDown(e) {
+  // Escape key closes the dialog.
+  if (e.keyCode == 27 && !e.shiftKey && !e.ctrlKey && !e.altKey && !e.metaKey) {
+    cr.dispatchSimpleEvent(document, 'disableCancelButton');

[dpapad, 2011/10/10 19:53:24]

Is it necessary to disable the cancel button here, since the tab is going to
close anyway?

[Lei Zhang, 2011/10/10 20:03:14]

Not sure. If the user presses escape many times quickly, is it possible for the
JS to call closePrintPreviewTab() twice? I'm just trying to play it safe.

+    closePrintPreviewTab();
+    return

[dpapad, 2011/10/10 19:53:24]

Nit: semicolon.

[Lei Zhang, 2011/10/10 20:03:14]

Done.

+  }
+}
+
 window.addEventListener('DOMContentLoaded', onLoad);
+window.addEventListener('keydown', onKeyDown);
 
 /// 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"/>