diff --git a/src/plugins/coreplugin/sidebar.cpp b/src/plugins/coreplugin/sidebar.cpp
index 68ae83dca79..332aea38086 100644
--- a/src/plugins/coreplugin/sidebar.cpp
+++ b/src/plugins/coreplugin/sidebar.cpp
@@ -50,7 +50,8 @@ SideBarItem::~SideBarItem()
 }
 
 SideBar::SideBar(QList<SideBarItem*> itemList,
-                 QList<SideBarItem*> defaultVisible)
+                 QList<SideBarItem*> defaultVisible) :
+    m_closeWhenEmpty(false)
 {
     setOrientation(Qt::Vertical);
     foreach (SideBarItem *item, itemList) {
@@ -76,23 +77,64 @@ QStringList SideBar::availableItems() const
     return m_availableItems;
 }
 
+QStringList SideBar::unavailableItems() const
+{
+    return m_unavailableItems;
+}
+
+bool SideBar::closeWhenEmpty() const
+{
+    return m_closeWhenEmpty;
+}
+void SideBar::setCloseWhenEmpty(bool value)
+{
+    m_closeWhenEmpty = value;
+}
+
 void SideBar::makeItemAvailable(SideBarItem *item)
 {
     QMap<QString, SideBarItem*>::const_iterator it = m_itemMap.constBegin();
     while (it != m_itemMap.constEnd()) {
         if (it.value() == item) {
             m_availableItems.append(it.key());
+            m_unavailableItems.removeAll(it.key());
             qSort(m_availableItems);
+            emit availableItemsChanged();
+            //updateWidgets();
             break;
         }
         ++it;
     }
 }
 
+// sets a list of externally used, unavailable items. For example,
+// another sidebar could set
+void SideBar::setUnavailableItems(const QStringList &itemTitles)
+{
+    // re-enable previous items
+    foreach(const QString &title, m_unavailableItems)
+        m_availableItems.append(title);
+
+    m_unavailableItems.clear();
+
+    foreach (const QString &title, itemTitles) {
+        if (!m_unavailableItems.contains(title))
+            m_unavailableItems.append(title);
+        m_availableItems.removeAll(title);
+    }
+    qSort(m_availableItems);
+    updateWidgets();
+}
+
 SideBarItem *SideBar::item(const QString &title)
 {
     if (m_itemMap.contains(title)) {
         m_availableItems.removeAll(title);
+
+        if (!m_unavailableItems.contains(title))
+            m_unavailableItems.append(title);
+
+        emit availableItemsChanged();
         return m_itemMap.value(title);
     }
     return 0;
@@ -134,6 +176,9 @@ void SideBar::closeSubWidget()
             return;
         removeSideBarWidget(widget);
         updateWidgets();
+    } else {
+        if (m_closeWhenEmpty)
+            setVisible(false);
     }
 }
 
@@ -227,8 +272,6 @@ QMap<QString, Core::Command*> SideBar::shortcutMap() const
     return m_shortcutMap;
 }
 
-
-
 SideBarWidget::SideBarWidget(SideBar *sideBar, const QString &title)
     : m_currentItem(0)
     , m_sideBar(sideBar)
@@ -302,6 +345,7 @@ void SideBarWidget::setCurrentItem(const QString &title)
         return;
     removeCurrentItem();
     m_currentItem = item;
+
     layout()->addWidget(m_currentItem->widget());
 
     // Add buttons and remember their actions for later removal
@@ -359,8 +403,6 @@ Core::Command *SideBarWidget::command(const QString &title) const
     return 0;
 }
 
-
-
 ComboBox::ComboBox(SideBarWidget *sideBarWidget)
     : m_sideBarWidget(sideBarWidget)
 {
diff --git a/src/plugins/coreplugin/sidebar.h b/src/plugins/coreplugin/sidebar.h
index 05e9c411251..4b08e9eb2ef 100644
--- a/src/plugins/coreplugin/sidebar.h
+++ b/src/plugins/coreplugin/sidebar.h
@@ -98,9 +98,15 @@ public:
     ~SideBar();
 
     QStringList availableItems() const;
+    QStringList unavailableItems() const;
     void makeItemAvailable(SideBarItem *item);
+    void setUnavailableItems(const QStringList &itemTitles);
+
     SideBarItem *item(const QString &title);
 
+    bool closeWhenEmpty() const;
+    void setCloseWhenEmpty(bool value);
+
     void saveSettings(QSettings *settings, const QString &name);
     void readSettings(QSettings *settings, const QString &name);
 
@@ -109,6 +115,9 @@ public:
     void setShortcutMap(const QMap<QString, Core::Command*> &shortcutMap);
     QMap<QString, Core::Command*> shortcutMap() const;
 
+signals:
+    void availableItemsChanged();
+
 private slots:
     void splitSubWidget();
     void closeSubWidget();
@@ -120,11 +129,12 @@ private:
     void removeSideBarWidget(Internal::SideBarWidget *widget);
 
     QList<Internal::SideBarWidget*> m_widgets;
-
     QMap<QString, SideBarItem*> m_itemMap;
     QStringList m_availableItems;
+    QStringList m_unavailableItems;
     QStringList m_defaultVisible;
     QMap<QString, Core::Command*> m_shortcutMap;
+    bool m_closeWhenEmpty;
 };
 
 namespace Internal {
diff --git a/src/plugins/qmldesigner/designmodewidget.cpp b/src/plugins/qmldesigner/designmodewidget.cpp
index 2b41d624f08..b6819f0df77 100644
--- a/src/plugins/qmldesigner/designmodewidget.cpp
+++ b/src/plugins/qmldesigner/designmodewidget.cpp
@@ -578,11 +578,8 @@ void DesignModeWidget::setup()
     
     m_formEditorView = new FormEditorView(this);
 
-
-    //m_designToolBar = new QToolBar;
     m_fakeToolBar = Core::EditorManager::createToolBar(this);
 
-
     m_mainSplitter = new MiniSplitter(this);
     m_mainSplitter->setObjectName("mainSplitter");
 
@@ -590,34 +587,35 @@ void DesignModeWidget::setup()
     m_warningWidget = new DocumentWarningWidget(this);
     m_warningWidget->setVisible(false);
 
-    // Left area:
-
     Core::SideBarItem *navigatorItem = new Core::SideBarItem(m_navigator->widget());
     Core::SideBarItem *libraryItem = new Core::SideBarItem(m_itemLibrary.data());
     Core::SideBarItem *propertiesItem = new Core::SideBarItem(m_allPropertiesBox.data());
 
+    QList<Core::SideBarItem*> sideBarItems;
 
-    QList<Core::SideBarItem*> leftSideBarItems, rightSideBarItems;
-    leftSideBarItems << navigatorItem << libraryItem;
-    rightSideBarItems << propertiesItem;
+    // default items
+    sideBarItems << navigatorItem << libraryItem << propertiesItem;
 
     if (projectsExplorer) {
         Core::SideBarItem *projectExplorerItem = new Core::SideBarItem(projectsExplorer);
-        rightSideBarItems << projectExplorerItem;
+        sideBarItems << projectExplorerItem;
     }
 
     if (fileSystemExplorer) {
         Core::SideBarItem *fileSystemExplorerItem = new Core::SideBarItem(fileSystemExplorer);
-        rightSideBarItems << fileSystemExplorerItem;
+        sideBarItems << fileSystemExplorerItem;
     }
 
-     if (openDocumentsWidget) {
+    if (openDocumentsWidget) {
         Core::SideBarItem *openDocumentsItem = new Core::SideBarItem(openDocumentsWidget);
-        rightSideBarItems << openDocumentsItem;
+        sideBarItems << openDocumentsItem;
     }
 
-    m_leftSideBar = new Core::SideBar(leftSideBarItems, QList<Core::SideBarItem*>() << navigatorItem << libraryItem);
-    m_rightSideBar = new Core::SideBar(rightSideBarItems, QList<Core::SideBarItem*>() << propertiesItem);
+    m_leftSideBar = new Core::SideBar(sideBarItems, QList<Core::SideBarItem*>() << navigatorItem << libraryItem);
+    m_rightSideBar = new Core::SideBar(sideBarItems, QList<Core::SideBarItem*>() << propertiesItem);
+
+    connect(m_leftSideBar, SIGNAL(availableItemsChanged()), SLOT(updateAvailableSidebarItemsRight()));
+    connect(m_rightSideBar, SIGNAL(availableItemsChanged()), SLOT(updateAvailableSidebarItemsLeft()));
 
     m_fakeToolBar->setToolbarCreationFlags(Core::EditorToolBar::FlagsStandalone);
     //m_fakeToolBar->addEditor(textEditor()); ### what does this mean?
@@ -664,6 +662,8 @@ void DesignModeWidget::setup()
     m_statesEditorWidget->setEnabled(true);
     m_leftSideBar->setEnabled(true);
     m_rightSideBar->setEnabled(true);
+    m_leftSideBar->setCloseWhenEmpty(true);
+    m_rightSideBar->setCloseWhenEmpty(true);
 
     readSettings();
 
@@ -671,6 +671,18 @@ void DesignModeWidget::setup()
     QApplication::processEvents();
 }
 
+void DesignModeWidget::updateAvailableSidebarItemsRight()
+{
+    // event comes from m_leftSidebar, so update right side.
+    m_rightSideBar->setUnavailableItems(m_leftSideBar->unavailableItems());
+}
+
+void DesignModeWidget::updateAvailableSidebarItemsLeft()
+{
+    // event comes from m_rightSidebar, so update left side.
+    m_leftSideBar->setUnavailableItems(m_rightSideBar->unavailableItems());
+}
+
 void DesignModeWidget::resizeEvent(QResizeEvent *event)
 {
     if (m_warningWidget)
diff --git a/src/plugins/qmldesigner/designmodewidget.h b/src/plugins/qmldesigner/designmodewidget.h
index 3130011bdc8..81fa1ae4de1 100644
--- a/src/plugins/qmldesigner/designmodewidget.h
+++ b/src/plugins/qmldesigner/designmodewidget.h
@@ -138,6 +138,8 @@ private slots:
     void enable();
     void disable(const QList<RewriterView::Error> &errors);
     void updateErrorStatus(const QList<RewriterView::Error> &errors);
+    void updateAvailableSidebarItemsLeft();
+    void updateAvailableSidebarItemsRight();
 
 protected:
     void resizeEvent(QResizeEvent *event);