Bug 342169 Disable "Undo Close Tab" if no tabs to restore (r=mconnor)

browser/base/content/browser.js

@@ -6673,10 +6673,21 @@ window.controllers.appendController(BrowserController);
  * This object is for augmenting tabs
  */
 var AugmentTabs = {
+
+  tabContextMenu: null,
+  undoCloseTabMenu: null,
+
   /**
    * Called in delayedStartup
    */
   init: function at_init() {
+    // get tab context menu
+    var tabbrowser = getBrowser();
+    this.tabContextMenu = document.getAnonymousElementByAttribute(tabbrowser, "anonid", "tabContextMenu");
+
+    // listen for tab-context menu showing
+    this.tabContextMenu.addEventListener("popupshowing", this.onTabContextMenuLoad, false);
+
     // add the tab context menu for undo-close-tab (bz254021)
     var ssEnabled = true;
     var prefBranch = Cc["@mozilla.org/preferences-service;1"].
@@ -6693,10 +6704,6 @@ var AugmentTabs = {
    * Add undo-close-tab to tab context menu
    */
   _addUndoCloseTabContextMenu: function at_addUndoCloseTabContextMenu() {
-    // get tab context menu
-    var tabbrowser = getBrowser();
-    var tabMenu = document.getAnonymousElementByAttribute(tabbrowser,"anonid","tabContextMenu");
-
     // get strings 
     var menuLabel = gNavigatorBundle.getString("tabContext.undoCloseTab");
     var menuAccessKey = gNavigatorBundle.getString("tabContext.undoCloseTabAccessKey");
@@ -6708,8 +6715,8 @@ var AugmentTabs = {
     undoCloseTabItem.addEventListener("command", this.undoCloseTab, false);
 
     // add to tab context menu
-    var insertPos = tabMenu.lastChild.previousSibling;
-    tabMenu.insertBefore(undoCloseTabItem, insertPos);
+    var insertPos = this.tabContextMenu.lastChild.previousSibling;
+    this.undoCloseTabMenu = this.tabContextMenu.insertBefore(undoCloseTabItem, insertPos);
   },
 
   /**
@@ -6720,5 +6727,14 @@ var AugmentTabs = {
     var ss = Cc["@mozilla.org/browser/sessionstore;1"].
              getService(Ci.nsISessionStore);
     ss.undoCloseTab(window, 0);
+  },
+
+  onTabContextMenuLoad: function at_onTabContextMenuLoad() {
+    if (AugmentTabs.undoCloseTabMenu) {
+      // only add the menu of there are tabs to restore
+      var ss = Cc["@mozilla.org/browser/sessionstore;1"].
+               getService(Ci.nsISessionStore);
+      AugmentTabs.undoCloseTabMenu.hidden = !(ss.getClosedTabCount(window) > 0);
+    }
   }
 };

browser/components/sessionstore/nsISessionStore.idl

@@ -54,6 +54,11 @@ interface nsISessionStore : nsISupports
    */
   void init(in nsIDOMWindow aWindow);
 
+  /**
+   * Get the number of restore-able tabs for a window
+   */
+  unsigned long getClosedTabCount(in nsIDOMWindow aWindow);
+
   /**
    * @param aWindow
    *          The window to reopen a closed tab in.

browser/components/sessionstore/src/nsSessionStore.js

@@ -541,7 +541,7 @@ SessionStoreService.prototype = {
     
     // DOMNodeRemoved is received *twice* after closing a tab, only take the first
     var tabState = this._windows[aWindow.__SSi].tabs[aTab._tPos];
-    if (tabState) {
+    if (tabState && tabState.entries[0].url != "about:blank") {
       this._windows[aWindow.__SSi]._closedTabs.unshift({
         state: tabState,
         title: aTab.getAttribute("label"),