diff --git a/src/cantor.cpp b/src/cantor.cpp
index 8f892df0..6d5cb8cf 100644
--- a/src/cantor.cpp
+++ b/src/cantor.cpp
@@ -1,638 +1,641 @@
 /*
     This program is free software; you can redistribute it and/or
     modify it under the terms of the GNU General Public License
     as published by the Free Software Foundation; either version 2
     of the License, or (at your option) any later version.
 
     This program is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     GNU General Public License for more details.
 
     You should have received a copy of the GNU General Public License
     along with this program; if not, write to the Free Software
     Foundation, Inc., 51 Franklin Street, Fifth Floor,
     Boston, MA  02110-1301, USA.
 
     ---
     Copyright (C) 2009 Alexander Rieder <alexanderrieder@gmail.com>
  */
 #include "cantor.h"
 
 #include <KActionCollection>
 #include <KConfigDialog>
 #include <KConfigGroup>
 #include <KMessageBox>
 #include <KShortcutsDialog>
 #include <KStandardAction>
 #include <KNS3/DownloadDialog>
 #include <KParts/ReadWritePart>
 
 #include <QApplication>
 #include <QCloseEvent>
 #include <QDebug>
 #include <QDockWidget>
 #include <QDir>
 #include <QFileDialog>
 #include <QPushButton>
 #include <QGraphicsView>
 
 #include "lib/backend.h"
 #include "lib/panelpluginhandler.h"
 #include "lib/panelplugin.h"
 #include "lib/worksheetaccess.h"
 
 #include "settings.h"
 #include "ui_settings.h"
 #include "backendchoosedialog.h"
 
 CantorShell::CantorShell() : KParts::MainWindow(), m_part(nullptr)
 {
 
     // set the shell's ui resource file
     setXMLFile(QLatin1String("cantor_shell.rc"));
 
     // then, setup our actions
     setupActions();
 
     createGUI(nullptr);
 
     m_tabWidget=new QTabWidget(this);
     m_tabWidget->setTabsClosable(true);
     m_tabWidget->setMovable(true);
     m_tabWidget->setDocumentMode(true);
     setCentralWidget(m_tabWidget);
 
     connect(m_tabWidget, SIGNAL(currentChanged(int)), this, SLOT(activateWorksheet(int)));
     connect(m_tabWidget, SIGNAL(tabCloseRequested(int)), this, SLOT(closeTab(int)));
 
     // apply the saved mainwindow settings, if any, and ask the mainwindow
     // to automatically save settings if changed: window size, toolbar
     // position, icon size, etc.
     setAutoSaveSettings();
 
     setDockOptions(QMainWindow::AnimatedDocks|QMainWindow::AllowTabbedDocks|QMainWindow::VerticalTabs);
 }
 
 void CantorShell::load(const QUrl &url)
 {
     if (!m_part||!m_part->url().isEmpty() || m_part->isModified() )
     {
         addWorksheet(QLatin1String("null"));
         m_tabWidget->setCurrentIndex(m_parts.size()-1);
     }
     m_part->openUrl( url );
 }
 
 bool CantorShell::hasAvailableBackend()
 {
     bool hasBackend=false;
     foreach(Cantor::Backend* b, Cantor::Backend::availableBackends())
     {
         if(b->isEnabled())
             hasBackend=true;
     }
 
     return hasBackend;
 }
 
 void CantorShell::setupActions()
 {
     QAction* openNew = KStandardAction::openNew(this, SLOT(fileNew()), actionCollection());
     openNew->setPriority(QAction::LowPriority);
     QAction* open = KStandardAction::open(this, SLOT(fileOpen()), actionCollection());
     open->setPriority(QAction::LowPriority);
 
     KStandardAction::close (this,  SLOT(closeTab()),  actionCollection());
 
     KStandardAction::quit(qApp, SLOT(closeAllWindows()), actionCollection());
 
     createStandardStatusBarAction();
     //setStandardToolBarMenuEnabled(true);
 
     KStandardAction::keyBindings(this, SLOT(optionsConfigureKeys()), actionCollection());
     KStandardAction::configureToolbars(this, SLOT(configureToolbars()), actionCollection());
 
     KStandardAction::preferences(this, SLOT(showSettings()), actionCollection());
 
     QAction * downloadExamples = new QAction(i18n("Download Example Worksheets"), actionCollection());
     downloadExamples->setIcon(QIcon::fromTheme(QLatin1String("get-hot-new-stuff")));
     actionCollection()->addAction(QLatin1String("file_example_download"),  downloadExamples);
     connect(downloadExamples, SIGNAL(triggered()), this,  SLOT(downloadExamples()));
 
     QAction * openExample =new QAction(i18n("&Open Example"), actionCollection());
     openExample->setIcon(QIcon::fromTheme(QLatin1String("document-open")));
     actionCollection()->addAction(QLatin1String("file_example_open"), openExample);
     connect(openExample, SIGNAL(triggered()), this, SLOT(openExample()));
 
     QAction* toPreviousTab = new QAction(i18n("Go to previous worksheet"), actionCollection());
     actionCollection()->addAction(QLatin1String("go_to_previous_tab"), toPreviousTab);
     actionCollection()->setDefaultShortcut(toPreviousTab, Qt::CTRL+Qt::Key_PageDown);
     connect(toPreviousTab, &QAction::triggered, toPreviousTab, [this](){
         const int index = m_tabWidget->currentIndex()-1;
         if (index >= 0)
             m_tabWidget->setCurrentIndex(index);
         else
             m_tabWidget->setCurrentIndex(m_tabWidget->count()-1);
     });
     addAction(toPreviousTab);
 
     QAction* toNextTab = new QAction(i18n("Go to next worksheet"), actionCollection());
     actionCollection()->addAction(QLatin1String("go_to_next_tab"), toNextTab);
     actionCollection()->setDefaultShortcut(toNextTab, Qt::CTRL+Qt::Key_PageUp);
     connect(toNextTab, &QAction::triggered, toNextTab, [this](){
         const int index = m_tabWidget->currentIndex()+1;
         if (index < m_tabWidget->count())
             m_tabWidget->setCurrentIndex(index);
         else
             m_tabWidget->setCurrentIndex(0);
     });
     addAction(toNextTab);
 }
 
 void CantorShell::saveProperties(KConfigGroup & /*config*/)
 {
     // the 'config' object points to the session managed
     // config file.  anything you write here will be available
     // later when this app is restored
 }
 
 void CantorShell::readProperties(const KConfigGroup & /*config*/)
 {
     // the 'config' object points to the session managed
     // config file.  this function is automatically called whenever
     // the app is being restored.  read in here whatever you wrote
     // in 'saveProperties'
 }
 
 void CantorShell::fileNew()
 {
     if (sender()->inherits("QAction"))
     {
         QAction * a = qobject_cast<QAction*>(sender());
         QString backendName = a->data().toString();
         if (!backendName.isEmpty())
         {
             addWorksheet(backendName);
             return;
         }
     }
     addWorksheet();
 }
 
 void CantorShell::optionsConfigureKeys()
 {
     KShortcutsDialog dlg( KShortcutsEditor::AllActions, KShortcutsEditor::LetterShortcutsDisallowed, this );
     dlg.addCollection( actionCollection(), i18n("Cantor") );
     if (m_part)
         dlg.addCollection( m_part->actionCollection(), i18n("Cantor") );
     dlg.configure( true );
 }
 
 void CantorShell::fileOpen()
 {
     // this slot is called whenever the File->Open menu is selected,
     // the Open shortcut is pressed (usually CTRL+O) or the Open toolbar
     // button is clicked
     QUrl url = QFileDialog::getOpenFileUrl(this, i18n("Open file"), QUrl(), i18n("Cantor Worksheet (*.cws)"));
 
     if (url.isEmpty() == false)
     {
         // About this function, the style guide (
         // http://developer.kde.org/documentation/standards/kde/style/basics/index.html )
         // says that it should open a new window if the document is _not_
         // in its initial state.  This is what we do here..
         /*if ( m_part->url().isEmpty() && ! m_part->isModified() )
         {
             // we open the file in this window...
             load( url );
         }
         else
         {
             // we open the file in a new window...
             CantorShell* newWin = new CantorShell;
             newWin->load( url );
             newWin->show();
             }*/
         load( url );
     }
 }
 
 void CantorShell::addWorksheet()
 {
     if(hasAvailableBackend()) //There is no point in asking for the backend, if no one is available
     {
         QString backend = Settings::self()->defaultBackend();
         if (backend.isEmpty())
         {
             QPointer<BackendChooseDialog> dlg=new BackendChooseDialog(this);
             if(dlg->exec())
             {
                 backend = dlg->backendName();
                 addWorksheet(backend);
             }
 
             delete dlg;
         }
         else
         {
             addWorksheet(backend);
         }
 
     }else
     {
         QTextBrowser *browser=new QTextBrowser(this);
         QString backendList=QLatin1String("<ul>");
         int backendListSize = 0;
         foreach(Cantor::Backend* b, Cantor::Backend::availableBackends())
         {
             if(!b->requirementsFullfilled()) //It's disabled because of misssing dependencies, not because of some other reason(like eg. nullbackend)
             {
                 backendList+=QString::fromLatin1("<li>%1: <a href=\"%2\">%2</a></li>").arg(b->name(), b->url());
                 ++backendListSize;
             }
         }
         browser->setHtml(i18np("<h1>No Backend Found</h1>\n"             \
                                "<div>You could try:\n"                   \
                                "  <ul>"                                  \
                                "    <li>Changing the settings in the config dialog;</li>" \
                                "    <li>Installing packages for the following program:</li>" \
                                "     %2 "                                \
                                "  </ul> "                                 \
                                "</div> "
                               , "<h1>No Backend Found</h1>\n"             \
                                "<div>You could try:\n"                   \
                                "  <ul>"                                  \
                                "    <li>Changing the settings in the config dialog;</li>" \
                                "    <li>Installing packages for one of the following programs:</li>" \
                                "     %2 "                                \
                                "  </ul> "                                 \
                                "</div> "
                               , backendListSize, backendList
                               ));
 
         browser->setObjectName(QLatin1String("ErrorMessage"));
         m_tabWidget->addTab(browser, i18n("Error"));
     }
 }
 
 void CantorShell::addWorksheet(const QString& backendName)
 {
     static int sessionCount=1;
 
     // this routine will find and load our Part.  it finds the Part by
     // name which is a bad idea usually.. but it's alright in this
     // case since our Part is made for this Shell
     KPluginFactory* factory = KPluginLoader(QLatin1String("libcantorpart")).factory();
     if (factory)
     {
-        // now that the Part is loaded, we cast it to a Part to get
-        // our hands on it
-        KParts::ReadWritePart* part = factory->create<KParts::ReadWritePart>(m_tabWidget, QVariantList()<<backendName);
+        Cantor::Backend* backend = Cantor::Backend::getBackend(backendName);
 
-        if (part)
+        if (backend)
         {
-            //determine backend
-            Cantor::Backend* backend = Cantor::Backend::getBackend(backendName);
-            // if backend not found, part is invalid, so delete it
-            if (backend)
+            if (backend->isEnabled() || backendName == QLatin1String("null"))
             {
-                connect(part, SIGNAL(setCaption(QString,QIcon)), this, SLOT(setTabCaption(QString,QIcon)));
-                m_parts.append(part);
-
-                int tab = m_tabWidget->addTab(part->widget(), QIcon::fromTheme(backend->icon()), i18n("Session %1", sessionCount++));
-                m_tabWidget->setCurrentIndex(tab);
-                // Setting focus on worksheet view, because Qt clear focus of added widget inside addTab
-                // This fix https://bugs.kde.org/show_bug.cgi?id=395976
-                part->widget()->findChild<QGraphicsView*>()->setFocus();
+                // now that the Part is loaded, we cast it to a Part to get our hands on it
+                KParts::ReadWritePart* part = factory->create<KParts::ReadWritePart>(m_tabWidget, QVariantList()<<backendName);
+                if (part)
+                {
+                    connect(part, SIGNAL(setCaption(QString,QIcon)), this, SLOT(setTabCaption(QString,QIcon)));
+                    m_parts.append(part);
+
+                    int tab = m_tabWidget->addTab(part->widget(), QIcon::fromTheme(backend->icon()), i18n("Session %1", sessionCount++));
+                    m_tabWidget->setCurrentIndex(tab);
+                    // Setting focus on worksheet view, because Qt clear focus of added widget inside addTab
+                    // This fix https://bugs.kde.org/show_bug.cgi?id=395976
+                    part->widget()->findChild<QGraphicsView*>()->setFocus();
+                }
+                else
+                {
+                    qDebug()<<"error creating part ";
+                }
             }
             else
-                delete part;
+            {
+                KMessageBox::error(this, i18n("%1 backend installed, but innactive. Please check installation and Cantor settings", backendName), i18n("Cantor"));
+            }
         }
         else
-        {
-            qDebug()<<"error creating part ";
-        }
-
+            KMessageBox::error(this, i18n("Backend %1 is not installed", backendName), i18n("Cantor"));
     }
     else
     {
         // if we couldn't find our Part, we exit since the Shell by
         // itself can't do anything useful
         KMessageBox::error(this, i18n("Could not find the Cantor Part."));
         qApp->quit();
         // we return here, cause qApp->quit() only means "exit the
         // next time we enter the event loop...
         return;
     }
 
 }
 
 void CantorShell::activateWorksheet(int index)
 {
     QObject* pluginHandler=m_part->findChild<QObject*>(QLatin1String("PanelPluginHandler"));
     if (pluginHandler)
         disconnect(pluginHandler,SIGNAL(pluginsChanged()), this, SLOT(updatePanel()));
 
     // Save part state before change worksheet
     if (m_part)
     {
         QStringList visiblePanelNames;
         foreach (QDockWidget* doc, m_panels)
         {
             if (doc->widget() && doc->widget()->isVisible())
                 visiblePanelNames << doc->objectName();
         }
         m_pluginsVisibility[m_part] = visiblePanelNames;
     }
 
     m_part=findPart(m_tabWidget->widget(index));
     if(m_part)
     {
         createGUI(m_part);
 
         QObject* pluginHandler=m_part->findChild<QObject*>(QLatin1String("PanelPluginHandler"));
         connect(pluginHandler, SIGNAL(pluginsChanged()), this, SLOT(updatePanel()));
         updatePanel();
     }
     else
         qDebug()<<"selected part doesn't exist";
 
     m_tabWidget->setCurrentIndex(index);
 }
 
 void CantorShell::setTabCaption(const QString& caption, const QIcon& icon)
 {
     if (caption.isEmpty()) return;
 
     KParts::ReadWritePart* part=dynamic_cast<KParts::ReadWritePart*>(sender());
     m_tabWidget->setTabText(m_tabWidget->indexOf(part->widget()), caption);
     m_tabWidget->setTabIcon(m_tabWidget->indexOf(part->widget()), icon);
 }
 
 void CantorShell::closeTab(int index)
 {
     if (!reallyClose(false))
     {
         return;
     }
 
     QWidget* widget = nullptr;
     if (index >= 0)
     {
         widget = m_tabWidget->widget(index);
     }
     else if (m_part)
     {
         widget = m_part->widget();
     }
 
     if (!widget)
     {
         qWarning() << "Could not find widget by tab index" << index;
         return;
     }
 
 
     m_tabWidget->removeTab(index);
 
     if(widget->objectName()==QLatin1String("ErrorMessage"))
     {
         widget->deleteLater();
     }else
     {
         KParts::ReadWritePart* part= findPart(widget);
         if(part)
         {
             m_parts.removeAll(part);
             m_pluginsVisibility.remove(part);
             delete part;
         }
     }
     updatePanel();
 }
 
 bool CantorShell::reallyClose(bool checkAllParts) {
     if(checkAllParts && m_parts.count() > 1) {
         bool modified = false;
         foreach( KParts::ReadWritePart* const part, m_parts)
         {
             if(part->isModified()) {
                 modified = true;
                 break;
             }
         }
         if(!modified) return true;
         int want_save = KMessageBox::warningYesNo( this,
             i18n("Multiple unsaved Worksheets are opened. Do you want to close them?"),
             i18n("Close Cantor"));
         switch (want_save) {
             case KMessageBox::Yes:
                 return true;
             case KMessageBox::No:
                 return false;
         }
     }
     if (m_part && m_part->isModified() ) {
         int want_save = KMessageBox::warningYesNoCancel( this,
             i18n("The current project has been modified. Do you want to save it?"),
             i18n("Save Project"));
         switch (want_save) {
             case KMessageBox::Yes:
                 m_part->save();
                 if(m_part->waitSaveComplete()) {
                     return true;
                 } else {
                     m_part->setModified(true);
                     return false;
                 }
             case KMessageBox::Cancel:
                 return false;
             case KMessageBox::No:
                 return true;
         }
     }
     return true;
 }
 
 void CantorShell::closeEvent(QCloseEvent* event) {
     if(!reallyClose()) {
         event->ignore();
     } else {
         KParts::MainWindow::closeEvent(event);
     }
 }
 
 void CantorShell::showSettings()
 {
     KConfigDialog *dialog = new KConfigDialog(this,  QLatin1String("settings"), Settings::self());
     QWidget *generalSettings = new QWidget;
     Ui::SettingsBase base;
     base.setupUi(generalSettings);
     base.kcfg_DefaultBackend->addItems(Cantor::Backend::listAvailableBackends());
 
     dialog->addPage(generalSettings, i18n("General"), QLatin1String("preferences-other"));
     foreach(Cantor::Backend* backend, Cantor::Backend::availableBackends())
     {
         if (backend->config()) //It has something to configure, so add it to the dialog
             dialog->addPage(backend->settingsWidget(dialog), backend->config(), backend->name(),  backend->icon());
     }
 
     dialog->show();
 }
 
 void CantorShell::downloadExamples()
 {
     KNS3::DownloadDialog dialog;
     dialog.exec();
     foreach (const KNS3::Entry& e,  dialog.changedEntries())
     {
         qDebug() << "Changed Entry: " << e.name();
     }
 }
 
 void CantorShell::openExample()
 {
     QString dir = QStandardPaths::writableLocation(QStandardPaths::DataLocation) + QLatin1String("/examples");
     if (dir.isEmpty()) return;
     QDir().mkpath(dir);
 
     QStringList files=QDir(dir).entryList(QDir::Files);
     QPointer<QDialog> dlg=new QDialog(this);
     QListWidget* list=new QListWidget(dlg);
     foreach(const QString& file, files)
     {
         QString name=file;
         name.remove(QRegExp(QLatin1String("-.*\\.hotstuff-access$")));
         list->addItem(name);
     }
 
     QVBoxLayout *mainLayout = new QVBoxLayout;
     dlg->setLayout(mainLayout);
     mainLayout->addWidget(list);
 
     QDialogButtonBox *buttonBox = new QDialogButtonBox(QDialogButtonBox::Ok | QDialogButtonBox::Cancel);
 
     mainLayout->addWidget(buttonBox);
 
     buttonBox->button(QDialogButtonBox::Ok)->setIcon(QApplication::style()->standardIcon(QStyle::SP_DialogOkButton));
     buttonBox->button(QDialogButtonBox::Cancel)->setIcon(QApplication::style()->standardIcon(QStyle::SP_DialogCancelButton));
 
     connect(buttonBox, SIGNAL(accepted()), dlg, SLOT(accept()) );
     connect(buttonBox, SIGNAL(rejected()), dlg, SLOT(reject()) );
 
     if (dlg->exec()==QDialog::Accepted&&list->currentRow()>=0)
     {
         const QString& selectedFile=files[list->currentRow()];
         QUrl url = QUrl::fromLocalFile(QDir(dir).absoluteFilePath(selectedFile));
 
         qDebug()<<"loading file "<<url;
         load(url);
     }
 
     delete dlg;
 }
 
 KParts::ReadWritePart* CantorShell::findPart(QWidget* widget)
 {
     foreach( KParts::ReadWritePart* const part, m_parts)
     {
         if(part->widget()==widget)
             return part;
     }
     return nullptr;
 }
 
 void CantorShell::updatePanel()
 {
     unplugActionList(QLatin1String("view_show_panel_list"));
 
     //remove all of the previous panels (but do not delete the widgets)
     foreach(QDockWidget* dock, m_panels)
     {
         QWidget* widget=dock->widget();
         if(widget!=nullptr)
         {
             widget->setParent(this);
             widget->hide();
         }
         dock->deleteLater();
     }
     m_panels.clear();
 
     QList<QAction*> panelActions;
 
     Cantor::PanelPluginHandler* handler=m_part->findChild<Cantor::PanelPluginHandler*>(QLatin1String("PanelPluginHandler"));
     if(!handler)
     {
         qDebug()<<"no PanelPluginHandle found for this part";
         return;
     }
 
     QDockWidget* last=nullptr;
 
     QList<Cantor::PanelPlugin*> plugins=handler->plugins();
     const bool isNewWorksheet = !m_pluginsVisibility.contains(m_part);
     foreach(Cantor::PanelPlugin* plugin, plugins)
     {
         if(plugin==nullptr)
         {
             qDebug()<<"somethings wrong";
             continue;
         }
 
         qDebug()<<"adding panel for "<<plugin->name();
         plugin->setParentWidget(this);
 
         QDockWidget* docker=new QDockWidget(plugin->name(), this);
         docker->setObjectName(plugin->name());
         docker->setWidget(plugin->widget());
         addDockWidget ( Qt::RightDockWidgetArea,  docker );
 
         // Set visibility for dock from saved info
         if (!isNewWorksheet)
             if (m_pluginsVisibility[m_part].contains(plugin->name()))
                 docker->show();
             else
                 docker->hide();
         else
             docker->show();
 
         if(last!=nullptr)
             tabifyDockWidget(last, docker);
         last=docker;
 
         connect(plugin, SIGNAL(visibilityRequested()), docker, SLOT(raise()));
 
         m_panels.append(docker);
 
         //Create the action to show/hide this panel
         panelActions<<docker->toggleViewAction();
 
     }
 
     plugActionList(QLatin1String("view_show_panel_list"), panelActions);
 
     unplugActionList(QLatin1String("new_worksheet_with_backend_list"));
     QList<QAction*> newBackendActions;
     foreach (Cantor::Backend* backend, Cantor::Backend::availableBackends())
     {
         if (!backend->isEnabled())
             continue;
         QAction * action = new QAction(QIcon::fromTheme(backend->icon()), backend->name(), nullptr);
         action->setData(backend->name());
         connect(action, SIGNAL(triggered()), this, SLOT(fileNew()));
         newBackendActions << action;
     }
     plugActionList(QLatin1String("new_worksheet_with_backend_list"), newBackendActions);
 }
 
 Cantor::WorksheetAccessInterface* CantorShell::currentWorksheetAccessInterface()
 {
     Cantor::WorksheetAccessInterface* wa=m_part->findChild<Cantor::WorksheetAccessInterface*>(Cantor::WorksheetAccessInterface::Name);
 
     if (!wa)
         qDebug()<<"failed to access worksheet access interface for current part";
 
     return wa;
 }
diff --git a/src/cantor_part.cpp b/src/cantor_part.cpp
index aef08c31..30d32538 100644
--- a/src/cantor_part.cpp
+++ b/src/cantor_part.cpp
@@ -1,976 +1,960 @@
 /*
     This program is free software; you can redistribute it and/or
     modify it under the terms of the GNU General Public License
     as published by the Free Software Foundation; either version 2
     of the License, or (at your option) any later version.
 
     This program is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     GNU General Public License for more details.
 
     You should have received a copy of the GNU General Public License
     along with this program; if not, write to the Free Software
     Foundation, Inc., 51 Franklin Street, Fifth Floor,
     Boston, MA  02110-1301, USA.
 
     ---
     Copyright (C) 2009 Alexander Rieder <alexanderrieder@gmail.com>
 */
 
 #include "cantor_part.h"
 
 #include <config-cantor.h>
 
 #include <KLocalizedString>
 #include <QIcon>
 #include <KParts/Event>
 #include <KParts/GUIActivateEvent>
 #include <KPluginFactory>
 #include <KAboutData>
 
 #include <QAction>
 #include <KActionCollection>
 #include <QFileDialog>
 #include <KStandardAction>
 #include <KZip>
 #include <KToggleAction>
 #include <KService>
 #include <KServiceTypeTrader>
 #include <KRun>
 #include <QProgressDialog>
 #include <KMessageBox>
 #include <KNS3/UploadDialog>
 #include <KXMLGUIFactory>
 
 #include <QElapsedTimer>
 #include <QFile>
 #include <QTextStream>
 #include <QTextEdit>
 #include <QTimer>
 #include <QPrinter>
 #include <QPrintPreviewDialog>
 #include <QPrintDialog>
 #include <QVBoxLayout>
 
 #include "worksheet.h"
 #include "worksheetview.h"
 #include "searchbar.h"
 #include "scripteditor/scripteditorwidget.h"
 #include "lib/backend.h"
 #include "lib/extension.h"
 #include "lib/assistant.h"
 #include "lib/panelpluginhandler.h"
 #include "lib/panelplugin.h"
 #include "lib/worksheetaccess.h"
 
 #include "settings.h"
 
 
 //A concrete implementation of the WorksheetAccesssInterface
 class WorksheetAccessInterfaceImpl : public Cantor::WorksheetAccessInterface
 {
 
   public:
     WorksheetAccessInterfaceImpl(QObject* parent, Worksheet* worksheet) :   WorksheetAccessInterface(parent),  m_worksheet(worksheet)
     {
         qDebug()<<"new worksheetaccess interface";
         connect(worksheet, SIGNAL(modified()), this, SIGNAL(modified()));
     }
 
     ~WorksheetAccessInterfaceImpl() override = default;
 
     QByteArray saveWorksheetToByteArray() override
     {
         return m_worksheet->saveToByteArray();
     }
 
     void loadWorksheetFromByteArray(QByteArray* data) override
     {
         m_worksheet->load(data);
     }
 
     Cantor::Session* session() override
     {
         return m_worksheet->session();
     }
 
   void evaluate() override
     {
         m_worksheet->evaluate();
     }
 
     void interrupt() override
     {
         m_worksheet->interrupt();
     }
 
   private:
     Worksheet* m_worksheet;
 };
 
 CantorPart::CantorPart( QWidget *parentWidget, QObject *parent, const QVariantList & args ): KParts::ReadWritePart(parent),
     m_searchBar(nullptr),
     m_initProgressDlg(nullptr),
     m_showProgressDlg(true),
     m_showBackendHelp(nullptr),
     m_statusBarBlocked(false),
     m_sessionStatusCounter(0)
 {
     m_panelHandler=new Cantor::PanelPluginHandler(this);
     connect(m_panelHandler, SIGNAL(pluginsChanged()), this, SLOT(pluginsChanged()));
 
     QString backendName;
     if(args.isEmpty())
         backendName=QLatin1String("null");
     else
         backendName=args.first().toString();
 
     for (const QVariant& arg : args)
     {
         if (arg.toString() == QLatin1String("--noprogress") )
         {
             qWarning()<<"not showing the progress bar by request";
             m_showProgressDlg=false;
         }
     }
 
     Cantor::Backend* b=Cantor::Backend::getBackend(backendName);
-    if(!b)
-    {
-        KMessageBox::error(parentWidget, i18n("Backend %1 is not installed", backendName), i18n("Error - Cantor"));
-        setWidget(new QWidget(parentWidget));
-        return;
-    }
-
-    if (b && !b->isEnabled() && backendName != QLatin1String("null"))
-    {
-        KMessageBox::information(parentWidget, i18n("There are some problems with the %1 backend,\n"\
-                                     "please check your configuration or install the needed packages.\n"
-                                     "You will only be able to view this worksheet.", backendName), i18n("Cantor"));
-        setWidget(new QWidget(parentWidget));
-        return;
-    }
-
     qDebug()<<"Backend "<<b->name()<<" offers extensions: "<<b->extensions();
 
 
     auto* collection = actionCollection();
 
     //central widget
     QWidget* widget = new QWidget(parentWidget);
     QVBoxLayout* layout = new QVBoxLayout(widget);
     m_worksheet=new Worksheet(b, widget);
     m_worksheetview=new WorksheetView(m_worksheet, widget);
     m_worksheetview->setEnabled(false); //disable input until the session has successfully logged in and emits the ready signal
     connect(m_worksheet, SIGNAL(modified()), this, SLOT(setModified()));
     connect(m_worksheet, SIGNAL(showHelp(QString)), this, SIGNAL(showHelp(QString)));
     connect(m_worksheet, SIGNAL(loaded()), this, SLOT(initialized()));
     connect(collection, SIGNAL(inserted(QAction*)), m_worksheet, SLOT(registerShortcut(QAction*)));
     layout->addWidget(m_worksheetview);
     setWidget(widget);
 
     //create WorksheetAccessInterface, used at the moment by LabPlot only to access Worksheet's API
     Cantor::WorksheetAccessInterface* iface = new WorksheetAccessInterfaceImpl(this, m_worksheet);
     Q_UNUSED(iface);
 
     //initialize actions
     m_worksheet->createActions(collection);
 
     KStandardAction::saveAs(this, SLOT(fileSaveAs()), collection);
     m_save = KStandardAction::save(this, SLOT(save()), collection);
     m_save->setPriority(QAction::LowPriority);
 
     QAction* savePlain = new QAction(i18n("Save Plain Text"), collection);
     collection->addAction(QLatin1String("file_save_plain"), savePlain);
     savePlain->setIcon(QIcon::fromTheme(QLatin1String("document-save")));
     connect(savePlain, SIGNAL(triggered()), this, SLOT(fileSavePlain()));
 
     QAction* undo = KStandardAction::undo(m_worksheet, SIGNAL(undo()), collection);
     undo->setPriority(QAction::LowPriority);
     connect(m_worksheet, SIGNAL(undoAvailable(bool)), undo, SLOT(setEnabled(bool)));
     m_editActions.push_back(undo);
 
     QAction* redo = KStandardAction::redo(m_worksheet, SIGNAL(redo()), collection);
     redo->setPriority(QAction::LowPriority);
     connect(m_worksheet, SIGNAL(redoAvailable(bool)), redo, SLOT(setEnabled(bool)));
     m_editActions.push_back(redo);
 
     QAction* cut = KStandardAction::cut(m_worksheet, SIGNAL(cut()), collection);
     cut->setPriority(QAction::LowPriority);
     connect(m_worksheet, SIGNAL(cutAvailable(bool)), cut, SLOT(setEnabled(bool)));
     m_editActions.push_back(cut);
 
     QAction* copy = KStandardAction::copy(m_worksheet, SIGNAL(copy()), collection);
     copy->setPriority(QAction::LowPriority);
     connect(m_worksheet, SIGNAL(copyAvailable(bool)), copy, SLOT(setEnabled(bool)));
 
     QAction* paste = KStandardAction::paste(m_worksheet, SLOT(paste()), collection);
     paste->setPriority(QAction::LowPriority);
     connect(m_worksheet, SIGNAL(pasteAvailable(bool)), paste, SLOT(setEnabled(bool)));
     m_editActions.push_back(paste);
 
     QAction* find = KStandardAction::find(this, SLOT(showSearchBar()), collection);
     find->setPriority(QAction::LowPriority);
 
     QAction* replace = KStandardAction::replace(this, SLOT(showExtendedSearchBar()), collection);
     replace->setPriority(QAction::LowPriority);
     m_editActions.push_back(replace);
 
     m_findNext = KStandardAction::findNext(this, SLOT(findNext()), collection);
     m_findNext->setEnabled(false);
 
     m_findPrev = KStandardAction::findPrev(this, SLOT(findPrev()), collection);
     m_findPrev->setEnabled(false);
 
     QAction* latexExport = new QAction(i18n("Export to LaTeX"), collection);
     collection->addAction(QLatin1String("file_export_latex"), latexExport);
     latexExport->setIcon(QIcon::fromTheme(QLatin1String("document-export")));
     connect(latexExport, SIGNAL(triggered()), this, SLOT(exportToLatex()));
 
     QAction* print = KStandardAction::print(this, SLOT(print()), collection);
     print->setPriority(QAction::LowPriority);
 
     QAction* printPreview = KStandardAction::printPreview(this, SLOT(printPreview()), collection);
     printPreview->setPriority(QAction::LowPriority);
 
     KStandardAction::zoomIn(m_worksheetview, SLOT(zoomIn()), collection);
     KStandardAction::zoomOut(m_worksheetview, SLOT(zoomOut()), collection);
     KStandardAction::actualSize(m_worksheetview, SLOT(actualSize()), collection);
 
     m_evaluate = new QAction(i18n("Evaluate Worksheet"), collection);
     collection->addAction(QLatin1String("evaluate_worksheet"), m_evaluate);
     m_evaluate->setIcon(QIcon::fromTheme(QLatin1String("system-run")));
     collection->setDefaultShortcut(m_evaluate, Qt::CTRL+Qt::Key_E);
     connect(m_evaluate, SIGNAL(triggered()), this, SLOT(evaluateOrInterrupt()));
     m_editActions.push_back(m_evaluate);
 
     m_typeset = new KToggleAction(i18n("Typeset using LaTeX"), collection);
     m_typeset->setChecked(Settings::self()->typesetDefault());
     // Disable until login, because we use session command for this action
     m_typeset->setEnabled(false);
     collection->addAction(QLatin1String("enable_typesetting"), m_typeset);
     connect(m_typeset, SIGNAL(toggled(bool)), this, SLOT(enableTypesetting(bool)));
 
     m_highlight = new KToggleAction(i18n("Syntax Highlighting"), collection);
     m_highlight->setChecked(Settings::self()->highlightDefault());
     collection->addAction(QLatin1String("enable_highlighting"), m_highlight);
     connect(m_highlight, SIGNAL(toggled(bool)), m_worksheet, SLOT(enableHighlighting(bool)));
 
     m_completion = new KToggleAction(i18n("Completion"), collection);
     m_completion->setChecked(Settings::self()->completionDefault());
     collection->addAction(QLatin1String("enable_completion"), m_completion);
     connect(m_completion, SIGNAL(toggled(bool)), m_worksheet, SLOT(enableCompletion(bool)));
 
     m_exprNumbering = new KToggleAction(i18n("Line Numbers"), collection);
     m_exprNumbering->setChecked(Settings::self()->expressionNumberingDefault());
     collection->addAction(QLatin1String("enable_expression_numbers"), m_exprNumbering);
     connect(m_exprNumbering, SIGNAL(toggled(bool)), m_worksheet, SLOT(enableExpressionNumbering(bool)));
 
     m_animateWorksheet = new KToggleAction(i18n("Animate Worksheet"), collection);
     m_animateWorksheet->setChecked(Settings::self()->animationDefault());
     collection->addAction(QLatin1String("enable_animations"), m_animateWorksheet);
     connect(m_animateWorksheet, SIGNAL(toggled(bool)), m_worksheet, SLOT(enableAnimations(bool)));
 
     m_restart = new QAction(i18n("Restart Backend"), collection);
     collection->addAction(QLatin1String("restart_backend"), m_restart);
     m_restart->setIcon(QIcon::fromTheme(QLatin1String("system-reboot")));
     connect(m_restart, SIGNAL(triggered()), this, SLOT(restartBackend()));
     m_restart->setEnabled(false); // No need show restart button before login
     m_editActions.push_back(m_restart);
 
     QAction* evaluateCurrent = new QAction(QIcon::fromTheme(QLatin1String("media-playback-start")), i18n("Evaluate Entry"), collection);
     collection->addAction(QLatin1String("evaluate_current"),  evaluateCurrent);
     collection->setDefaultShortcut(evaluateCurrent, Qt::SHIFT + Qt::Key_Return);
     connect(evaluateCurrent, SIGNAL(triggered()), m_worksheet, SLOT(evaluateCurrentEntry()));
     m_editActions.push_back(evaluateCurrent);
 
     QAction* insertCommandEntry = new QAction(QIcon::fromTheme(QLatin1String("run-build")), i18n("Insert Command Entry"), collection);
     collection->addAction(QLatin1String("insert_command_entry"),  insertCommandEntry);
     collection->setDefaultShortcut(insertCommandEntry, Qt::CTRL + Qt::Key_Return);
     connect(insertCommandEntry, SIGNAL(triggered()), m_worksheet, SLOT(insertCommandEntry()));
     m_editActions.push_back(insertCommandEntry);
 
     QAction* insertTextEntry = new QAction(QIcon::fromTheme(QLatin1String("draw-text")), i18n("Insert Text Entry"), collection);
     collection->addAction(QLatin1String("insert_text_entry"),  insertTextEntry);
     connect(insertTextEntry, SIGNAL(triggered()), m_worksheet, SLOT(insertTextEntry()));
     m_editActions.push_back(insertTextEntry);
 
 #ifdef Discount_FOUND
     QAction* insertMarkdownEntry = new QAction(QIcon::fromTheme(QLatin1String("text-x-markdown")), i18n("Insert Markdown Entry"), collection);
     collection->addAction(QLatin1String("insert_markdown_entry"),  insertMarkdownEntry);
     connect(insertMarkdownEntry, SIGNAL(triggered()), m_worksheet, SLOT(insertMarkdownEntry()));
     m_editActions.push_back(insertMarkdownEntry);
 #endif
 
 #ifdef WITH_EPS
     QAction* insertLatexEntry = new QAction(QIcon::fromTheme(QLatin1String("text-x-tex")), i18n("Insert Latex Entry"), collection);
     collection->addAction(QLatin1String("insert_latex_entry"),  insertLatexEntry);
     connect(insertLatexEntry, SIGNAL(triggered()), m_worksheet, SLOT(insertLatexEntry()));
     m_editActions.push_back(insertLatexEntry);
 #endif
 
     QAction* insertPageBreakEntry = new QAction(QIcon::fromTheme(QLatin1String("go-next-view-page")), i18n("Insert Page Break"), collection);
     collection->addAction(QLatin1String("insert_page_break_entry"), insertPageBreakEntry);
     connect(insertPageBreakEntry, SIGNAL(triggered()), m_worksheet, SLOT(insertPageBreakEntry()));
     m_editActions.push_back(insertPageBreakEntry);
 
     QAction* insertImageEntry = new QAction(QIcon::fromTheme(QLatin1String("image-x-generic")), i18n("Insert Image"), collection);
     collection->addAction(QLatin1String("insert_image_entry"), insertImageEntry);
     connect(insertImageEntry, SIGNAL(triggered()), m_worksheet, SLOT(insertImageEntry()));
     m_editActions.push_back(insertImageEntry);
 
     QAction* removeCurrent = new QAction(QIcon::fromTheme(QLatin1String("edit-delete")), i18n("Remove current Entry"), collection);
     collection->addAction(QLatin1String("remove_current"), removeCurrent);
     collection->setDefaultShortcut(removeCurrent, Qt::ShiftModifier + Qt::Key_Delete);
     connect(removeCurrent, SIGNAL(triggered()), m_worksheet, SLOT(removeCurrentEntry()));
     m_editActions.push_back(removeCurrent);
 
     m_showBackendHelp = new QAction(i18n("Show %1 Help", b->name()) , collection);
     m_showBackendHelp->setIcon(QIcon::fromTheme(QLatin1String("help-contents")));
     collection->addAction(QLatin1String("backend_help"), m_showBackendHelp);
     connect(m_showBackendHelp, SIGNAL(triggered()), this, SLOT(showBackendHelp()));
 
     // Disabled, because uploading to kde store from program don't work
     // See https://phabricator.kde.org/T9980 for details
     // If this situation will changed, then uncomment this action
     /*
     QAction* publishWorksheet = new QAction(i18n("Publish Worksheet"), collection);
     publishWorksheet->setIcon(QIcon::fromTheme(QLatin1String("get-hot-new-stuff")));
     collection->addAction(QLatin1String("file_publish_worksheet"), publishWorksheet);
     connect(publishWorksheet, SIGNAL(triggered()), this, SLOT(publishWorksheet()));
     */
 
     KToggleAction* showEditor = new KToggleAction(i18n("Show Script Editor"), collection);
     showEditor->setChecked(false);
     collection->addAction(QLatin1String("show_editor"), showEditor);
     connect(showEditor, SIGNAL(toggled(bool)), this, SLOT(showScriptEditor(bool)));
     showEditor->setEnabled(b->extensions().contains(QLatin1String("ScriptExtension")));
 
     QAction* showCompletion = new QAction(i18n("Show Completion"), collection);
     collection->addAction(QLatin1String("show_completion"), showCompletion);
     QList<QKeySequence> showCompletionShortcuts;
     showCompletionShortcuts << Qt::Key_Tab << Qt::CTRL + Qt::Key_Space;
     collection->setDefaultShortcuts(showCompletion, showCompletionShortcuts);
     connect(showCompletion, SIGNAL(triggered()), m_worksheet, SLOT(showCompletion()));
     m_editActions.push_back(showCompletion);
 
     // set our XML-UI resource file
     setXMLFile(QLatin1String("cantor_part.rc"));
 
     // we are read-write by default
     setReadWrite(true);
 
     // we are not modified since we haven't done anything yet
     setModified(false);
 
     initialized();
 }
 
 CantorPart::~CantorPart()
 {
     if (m_scriptEditor)
     {
         disconnect(m_scriptEditor, SIGNAL(destroyed()), this, SLOT(scriptEditorClosed()));
         delete m_scriptEditor;
     }
     if (m_searchBar)
         delete m_searchBar;
 }
 
 void CantorPart::setReadWrite(bool rw)
 {
     // notify your internal widget of the read-write state
     m_worksheetview->setInteractive(rw);
 
     ReadWritePart::setReadWrite(rw);
 }
 
 void CantorPart::setReadOnly()
 {
     for (QAction* action : m_editActions)
         action->setEnabled(false);
 
     if (m_showBackendHelp)
     {
         m_showBackendHelp->setEnabled(false);
         m_showBackendHelp->setVisible(false);
     }
 }
 
 void CantorPart::setModified(bool modified)
 {
     // get a handle on our Save action and make sure it is valid
     if (!m_save)
         return;
 
     // if so, we either enable or disable it based on the current state
     m_save->setEnabled(modified);
 
     // in any event, we want our parent to do it's thing
     ReadWritePart::setModified(modified);
 }
 
 KAboutData& CantorPart::createAboutData()
 {
     // the non-i18n name here must be the same as the directory in
     // which the part's rc file is installed ('partrcdir' in the Makefile)
     static KAboutData about(QLatin1String("cantorpart"),
                      QLatin1String("Cantor"),
                      QLatin1String(CANTOR_VERSION),
                      i18n("CantorPart"),
                      KAboutLicense::GPL,
                      i18n("(C) 2009-2015 Alexander Rieder"),
                      QString(),
                      QLatin1String("http://edu.kde.org/cantor"));
 
     about.addAuthor( i18n("Alexander Rieder"), QString(), QLatin1String("alexanderrieder@gmail.com") );
     return about;
 }
 
 bool CantorPart::openFile()
 {
     //don't crash if for some reason the worksheet is invalid
     if(m_worksheet==nullptr)
     {
         qWarning()<<"trying to open in an invalid cantor part";
         return false;
     }
 
     QApplication::setOverrideCursor(QCursor(Qt::WaitCursor));
     QElapsedTimer timer;
 	timer.start();
     const bool rc = m_worksheet->load(localFilePath());
     QApplication::restoreOverrideCursor();
 
     if (rc) {
         qDebug()<< "Worksheet successfully loaded in " <<  (float)timer.elapsed()/1000 << " seconds).";
         updateCaption();
         // We modified, but it we load file now, so no need in save option
         setModified(false);
     }
 
     return rc;
 }
 
 bool CantorPart::saveFile()
 {
     // if we aren't read-write, return immediately
     if (isReadWrite() == false)
         return false;
 
     qDebug()<<"saving to: "<<url();
     if (url().isEmpty())
         fileSaveAs();
     else
         m_worksheet->save( localFilePath() );
     setModified(false);
 
     return true;
 }
 
 void CantorPart::fileSaveAs()
 {
     // this slot is called whenever the File->Save As menu is selected
     QString worksheetFilter = i18n("Cantor Worksheet (*.cws)");
     QString filter = worksheetFilter;
 
     if (!m_worksheet->isReadOnly())
     {
         //if the backend supports scripts, also append their scriptFile endings to the filter
         Cantor::Backend * const backend=m_worksheet->session()->backend();
         if (backend->extensions().contains(QLatin1String("ScriptExtension")))
         {
             Cantor::ScriptExtension* e=dynamic_cast<Cantor::ScriptExtension*>(backend->extension(QLatin1String("ScriptExtension")));
             filter+=QLatin1String(";;")+e->scriptFileFilter();
         }
     }
 
     QString selectedFilter;
     QString file_name = QFileDialog::getSaveFileName(widget(), i18n("Save as"), QString(), filter, &selectedFilter);
     if (file_name.isEmpty())
         return;
 
     //depending on user's selection, save as a worksheet or as a plain script file
     if (selectedFilter == worksheetFilter)
     {
         if (!file_name.endsWith(QLatin1String(".cws")))
             file_name += QLatin1String(".cws");
         saveAs(QUrl::fromLocalFile(file_name));
     }
     else
         m_worksheet->savePlain(file_name);
 
     updateCaption();
 }
 
 void CantorPart::fileSavePlain()
 {
     QString file_name = QFileDialog::getSaveFileName(widget(), i18n("Save"), QString(), QString());
     if (!file_name.isEmpty())
         m_worksheet->savePlain(file_name);
 }
 
 void CantorPart::exportToLatex()
 {
     QString file_name = QFileDialog::getSaveFileName(widget(), i18n("Export to LaTeX"), QString(), QString());
 
     if (file_name.isEmpty() == false)
         {
         if (!file_name.endsWith(QLatin1String(".tex")))
             file_name += QLatin1String(".tex");
         m_worksheet->saveLatex(file_name);
         }
 }
 
 void CantorPart::guiActivateEvent( KParts::GUIActivateEvent * event )
 {
     KParts::ReadWritePart::guiActivateEvent(event);
     if(event->activated())
     {
         if(m_scriptEditor)
             m_scriptEditor->show();
     }else
     {
         if(m_scriptEditor)
             m_scriptEditor->hide();
     }
 }
 
 void CantorPart::evaluateOrInterrupt()
 {
     qDebug()<<"evalorinterrupt";
     if(m_worksheet->isRunning())
         m_worksheet->interrupt();
     else
         m_worksheet->evaluate();
 }
 void CantorPart::restartBackend()
 {
     bool restart = false;
     if (Settings::self()->warnAboutSessionRestart())
     {
         KMessageBox::ButtonCode tmp;
 
         // If we want the question box, but it is disable, then enable it
         if (!KMessageBox::shouldBeShownYesNo(QLatin1String("WarnAboutSessionRestart"), tmp))
             KMessageBox::enableMessage(QLatin1String("WarnAboutSessionRestart"));
 
         const QString& name = m_worksheet->session()->backend()->name();
         KMessageBox::ButtonCode rc = KMessageBox::questionYesNo(widget(),
             i18n("All the available calculation results will be lost. Do you really want to restart %1?", name),
             i18n("Restart %1?", name),
             KStandardGuiItem::yes(),
             KStandardGuiItem::no(),
             QLatin1String("WarnAboutSessionRestart")
         );
 
         // Update setting's value
         Settings::self()->setWarnAboutSessionRestart(
             KMessageBox::shouldBeShownYesNo(QLatin1String("WarnAboutSessionRestart"), tmp));
         Settings::self()->save();
 
         restart = rc == KMessageBox::ButtonCode::Yes;
     }
     else
     {
         KMessageBox::ButtonCode rc;
         KMessageBox::shouldBeShownYesNo(QLatin1String("WarnAboutSessionRestart"), rc);
         restart = rc == KMessageBox::ButtonCode::Yes;
     }
 
     if (restart)
     {
         m_worksheet->session()->logout();
         m_worksheet->loginToSession();
     }
 }
 
 void CantorPart::worksheetStatusChanged(Cantor::Session::Status status)
 {
     qDebug()<<"wsStatusChange"<<status;
     unsigned int count = ++m_sessionStatusCounter;
     if(status==Cantor::Session::Running)
     {
         // Useless add a interrupt action without delay, because user physically can't interrupt fast commands
         QTimer::singleShot(100, this, [this, count] () {
             if(m_worksheet->session()->status() == Cantor::Session::Running && m_sessionStatusCounter == count)
             {
                 m_evaluate->setText(i18n("Interrupt"));
                 m_evaluate->setShortcut(Qt::CTRL+Qt::Key_I);
                 m_evaluate->setIcon(QIcon::fromTheme(QLatin1String("dialog-close")));
                 setStatusMessage(i18n("Calculating..."));
             }
         });
     }else if (status==Cantor::Session::Done)
     {
         m_evaluate->setText(i18n("Evaluate Worksheet"));
         m_evaluate->setShortcut(Qt::CTRL+Qt::Key_E);
         m_evaluate->setIcon(QIcon::fromTheme(QLatin1String("system-run")));
 
         setStatusMessage(i18n("Ready"));
     }
 }
 
 void CantorPart::showSessionError(const QString& message)
 {
     qDebug()<<"Error: "<<message;
     initialized();
     showImportantStatusMessage(i18n("Session Error: %1", message));
 }
 
 void CantorPart::initialized()
 {
     if (!m_worksheet->isReadOnly())
     {
         connect(m_worksheet->session(), SIGNAL(statusChanged(Cantor::Session::Status)), this, SLOT(worksheetStatusChanged(Cantor::Session::Status)));
         connect(m_worksheet->session(), SIGNAL(loginStarted()),this, SLOT(worksheetSessionLoginStarted()));
         connect(m_worksheet->session(), SIGNAL(loginDone()),this, SLOT(worksheetSessionLoginDone()));
         connect(m_worksheet->session(), SIGNAL(error(QString)), this, SLOT(showSessionError(QString)));
 
         loadAssistants();
         m_panelHandler->setSession(m_worksheet->session());
         adjustGuiToSession();
 
         // Don't set modification flag, if we add command entry in empty worksheet
         const bool modified = this->isModified();
         if (m_worksheet->isEmpty())
             m_worksheet->appendCommandEntry();
         setModified(modified);
     }
     else
     {
         setReadOnly();
         // Clear assistants
         for (KXMLGUIClient* client: childClients())
         {
             Cantor::Assistant* assistant = dynamic_cast<Cantor::Assistant*>(client);
             if (assistant)
             {
                 factory()->removeClient(client);
                 removeChildClient(client);
                 assistant->deleteLater();
             }
         }
     }
 
     m_worksheetview->setEnabled(true);
     m_worksheetview->setFocus();
 
     setStatusMessage(i18n("Initialization complete"));
     updateCaption();
 }
 
 void CantorPart::worksheetSessionLoginStarted() {
     setStatusMessage(i18n("Initializing..."));
     QApplication::setOverrideCursor(QCursor(Qt::WaitCursor));
 }
 
 void CantorPart::worksheetSessionLoginDone() {
     setStatusMessage(i18n("Ready"));
 
     m_typeset->setEnabled(true);
     m_restart->setEnabled(true);
 
     QApplication::restoreOverrideCursor();
 }
 
 void CantorPart::enableTypesetting(bool enable)
 {
     m_worksheet->session()->setTypesettingEnabled(enable);
 }
 
 void CantorPart::showBackendHelp()
 {
     qDebug()<<"showing backends help";
     Cantor::Backend* backend=m_worksheet->session()->backend();
     QUrl url = backend->helpUrl();
     qDebug()<<"launching url "<<url;
     new KRun(url, widget());
 }
 
 Worksheet* CantorPart::worksheet()
 {
     return m_worksheet;
 }
 
 void CantorPart::updateCaption()
 {
     QString filename=url().fileName();
     //strip away the extension
     filename=filename.left(filename.lastIndexOf(QLatin1Char('.')));
 
     if (filename.isEmpty())
         filename=i18n("Unnamed");
 
     if (!m_worksheet->isReadOnly())
         emit setCaption(filename, QIcon::fromTheme(m_worksheet->session()->backend()->icon()));
     else
         emit setCaption(filename+QLatin1Char(' ')+i18n("[read-only]"), QIcon());
 }
 
 void CantorPart::pluginsChanged()
 {
     for (auto* plugin : m_panelHandler->plugins())
         connect(plugin, SIGNAL(requestRunCommand(QString)), this, SLOT(runCommand(QString)));
 }
 
 void CantorPart::loadAssistants()
 {
     qDebug()<<"loading assistants...";
 
     QStringList assistantDirs;
     for (const QString& dir : QCoreApplication::libraryPaths())
         assistantDirs << dir + QDir::separator() + QLatin1String("cantor/assistants");
 
     QPluginLoader loader;
     for (const QString& dir : assistantDirs) {
 
         qDebug() << "dir: " << dir;
         QStringList assistants;
         QDir assistantDir = QDir(dir);
 
         assistants = assistantDir.entryList();
 
         for (const QString& assistant : assistants) {
             if (assistant==QLatin1String(".") || assistant==QLatin1String(".."))
                 continue;
 
             loader.setFileName(dir + QDir::separator() + assistant);
 
             if (!loader.load()){
                 qDebug() << "Error while loading assistant: " << assistant;
                 continue;
             }
 
             KPluginFactory* factory = KPluginLoader(loader.fileName()).factory();
             Cantor::Assistant* plugin = factory->create<Cantor::Assistant>(this);
 
             Cantor::Backend* backend=worksheet()->session()->backend();
 
             KPluginMetaData info(loader);
             plugin->setPluginInfo(info);
             plugin->setBackend(backend);
 
             bool supported=true;
             for (const QString& req : plugin->requiredExtensions())
                 supported=supported && backend->extensions().contains(req);
 
             if(supported)
             {
                 qDebug() << "plugin " << info.name() << " is supported by " << backend->name() << ", requires extensions " << plugin->requiredExtensions();
                 plugin->initActions();
                 connect(plugin, SIGNAL(requested()), this, SLOT(runAssistant()));
             }else
             {
                 qDebug() << "plugin " << info.name() << " is not supported by "<<backend->name();
                 removeChildClient(plugin);
                 plugin->deleteLater();
             }
         }
     }
 }
 
 void CantorPart::runAssistant()
 {
     Cantor::Assistant* a=qobject_cast<Cantor::Assistant*>(sender());
     QStringList cmds=a->run(widget());
     qDebug()<<cmds;
     if(!cmds.isEmpty())
         runCommand(cmds.join(QLatin1String("\n")));
 }
 
 void CantorPart::runCommand(const QString& cmd)
 {
     m_worksheet->appendCommandEntry(cmd);
 }
 
 void CantorPart::showSearchBar()
 {
     if (!m_searchBar) {
         m_searchBar = new SearchBar(widget(), m_worksheet);
         widget()->layout()->addWidget(m_searchBar);
         connect(m_searchBar, SIGNAL(destroyed(QObject*)),
                 this, SLOT(searchBarDeleted()));
     }
 
     m_findNext->setEnabled(true);
     m_findPrev->setEnabled(true);
 
     m_searchBar->showStandard();
     m_searchBar->setFocus();
 }
 
 void CantorPart::showExtendedSearchBar()
 {
     if (!m_searchBar) {
         m_searchBar = new SearchBar(widget(), m_worksheet);
         widget()->layout()->addWidget(m_searchBar);
         connect(m_searchBar, SIGNAL(destroyed(QObject*)),
                 this, SLOT(searchBarDeleted()));
     }
 
     m_findNext->setEnabled(true);
     m_findPrev->setEnabled(true);
 
     m_searchBar->showExtended();
     m_searchBar->setFocus();
 }
 
 void CantorPart::findNext()
 {
     if (m_searchBar)
         m_searchBar->next();
 }
 
 void CantorPart::findPrev()
 {
     if (m_searchBar)
         m_searchBar->prev();
 }
 
 void CantorPart::searchBarDeleted()
 {
     m_searchBar = nullptr;
     m_findNext->setEnabled(false);
     m_findPrev->setEnabled(false);
 }
 
 void CantorPart::adjustGuiToSession()
 {
     Cantor::Backend::Capabilities capabilities = m_worksheet->session()->backend()->capabilities();
 #ifdef WITH_EPS
     m_typeset->setVisible(capabilities.testFlag(Cantor::Backend::LaTexOutput));
 #else
     m_typeset->setVisible(false);
 #endif
     m_completion->setVisible(capabilities.testFlag(Cantor::Backend::Completion));
 
     //this is 0 on the first call
     if(m_showBackendHelp)
         m_showBackendHelp->setText(i18n("Show %1 Help", m_worksheet->session()->backend()->name()));
 }
 
 void CantorPart::publishWorksheet()
 {
     int ret = KMessageBox::questionYesNo(widget(),
                                          i18n("Do you want to upload current Worksheet to public web server?"),
                                          i18n("Question - Cantor"));
     if (ret != KMessageBox::Yes) return;
 
     if (isModified()||url().isEmpty())
     {
         ret = KMessageBox::warningContinueCancel(widget(),
                                                  i18n("The Worksheet is not saved. You should save it before uploading."),
                                                  i18n("Warning - Cantor"),  KStandardGuiItem::save(),  KStandardGuiItem::cancel());
         if (ret != KMessageBox::Continue) return;
         if (!saveFile()) return;
     }
 
     qDebug()<<"uploading file "<<url();
 
     // upload
     //HACK: use different .knsrc files for each category
     //remove this once KNS3 gains the ability to select category
     KNS3::UploadDialog dialog(QString::fromLatin1("cantor_%1.knsrc").arg(m_worksheet->session()->backend()->id().toLower()), widget());
     dialog.setUploadFile(url());
     dialog.exec();
 }
 
 void CantorPart::print()
 {
     QPrinter printer;
     QPointer<QPrintDialog> dialog = new QPrintDialog(&printer,  widget());
 
     // TODO: Re-enable print selection
     //if (m_worksheet->textCursor().hasSelection())
     //    dialog->addEnabledOption(QAbstractPrintDialog::PrintSelection);
 
     if (dialog->exec() == QDialog::Accepted)
         m_worksheet->print(&printer);
 
     delete dialog;
 }
 
 void CantorPart::printPreview()
 {
     QPrintPreviewDialog *dialog = new QPrintPreviewDialog(widget());
     connect(dialog, SIGNAL(paintRequested(QPrinter*)), m_worksheet, SLOT(print(QPrinter*)));
     dialog->exec();
 }
 
 void CantorPart::showScriptEditor(bool show)
 {
     if(show)
     {
         if (m_scriptEditor)
         {
             return;
         }
         Cantor::ScriptExtension* scriptE=dynamic_cast<Cantor::ScriptExtension*>(m_worksheet->session()->backend()->extension(QLatin1String("ScriptExtension")));
         if (!scriptE)
         {
             return;
         }
         m_scriptEditor=new ScriptEditorWidget(scriptE->scriptFileFilter(), scriptE->highlightingMode(), widget()->window());
         connect(m_scriptEditor, SIGNAL(runScript(QString)), this, SLOT(runScript(QString)));
         connect(m_scriptEditor, SIGNAL(destroyed()), this, SLOT(scriptEditorClosed()));
         m_scriptEditor->show();
     }else
     {
         m_scriptEditor->deleteLater();
     }
 }
 
 void CantorPart::scriptEditorClosed()
 {
     QAction* showEditor = actionCollection()->action(QLatin1String("show_editor"));
     if (showEditor)
     {
         showEditor->setChecked(false);
     }
 }
 
 void CantorPart::runScript(const QString& file)
 {
     Cantor::Backend* backend=m_worksheet->session()->backend();
     if(!backend->extensions().contains(QLatin1String("ScriptExtension")))
     {
         KMessageBox::error(widget(), i18n("This backend does not support scripts."), i18n("Error - Cantor"));
         return;
     }
 
     Cantor::ScriptExtension* scriptE=dynamic_cast<Cantor::ScriptExtension*>(backend->extension(QLatin1String("ScriptExtension")));
     m_worksheet->appendCommandEntry(scriptE->runExternalScript(file));
 }
 
 void CantorPart::blockStatusBar()
 {
     m_statusBarBlocked=true;
 }
 
 void CantorPart::unblockStatusBar()
 {
     m_statusBarBlocked=false;
     if(!m_cachedStatusMessage.isNull())
         setStatusMessage(m_cachedStatusMessage);
     m_cachedStatusMessage.clear();
 }
 
 void CantorPart::setStatusMessage(const QString& message)
 {
     if(!m_statusBarBlocked)
         emit setStatusBarText(message);
     else
         m_cachedStatusMessage=message;
 }
 
 void CantorPart::showImportantStatusMessage(const QString& message)
 {
     setStatusMessage(message);
     blockStatusBar();
     QTimer::singleShot(3000, this, SLOT(unblockStatusBar()));
 }
 
 K_PLUGIN_FACTORY_WITH_JSON(CantorPartFactory, "cantor_part.json", registerPlugin<CantorPart>();)
 #include "cantor_part.moc"