Don't try to modify the worksheet when it's currently being destroyed.

BUG: 428611
FIXED-IN: 21.04

src/cantor_part.cpp

@@ -134,7 +134,8 @@ CantorPart::CantorPart( QWidget *parentWidget, QObject *parent, const QVariantLi
     if (!backendName.isEmpty())
     {
         b = Cantor::Backend::getBackend(backendName);
-        qDebug()<<"Backend "<<b->name()<<" offers extensions: "<<b->extensions();
+        if (b)
+            qDebug()<<"Backend "<<b->name()<<" offers extensions: "<<b->extensions();
     }
 
     //central widget
@@ -655,7 +656,8 @@ void CantorPart::worksheetStatusChanged(Cantor::Session::Status status)
 {
     qDebug()<<"wsStatusChange"<<status;
     unsigned int count = ++m_sessionStatusCounter;
-    if(status == Cantor::Session::Running)
+    switch (status) {
+    case Cantor::Session::Running:
     {
         // Useless add a interrupt action without delay, because user physically can't interrupt fast commands
         QTimer::singleShot(100, this, [this, count] () {
@@ -667,13 +669,19 @@ void CantorPart::worksheetStatusChanged(Cantor::Session::Status status)
                 setStatusMessage(i18n("Calculating..."));
             }
         });
-    }else if (status == Cantor::Session::Done)
+        break;
+    }
+    case 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"));
+        break;
+    }
+    case Cantor::Session::Disable:
+        setStatusMessage(QString()); //clean the status bar to remove the potential "Calculating...", etc. after the session was closed
     }
 }
 

src/worksheet.cpp

@@ -111,17 +111,13 @@ Worksheet::Worksheet(Cantor::Backend* backend, QWidget* parent, bool useDeafultW
 
 Worksheet::~Worksheet()
 {
+    m_isClosing = true;
+
     // This is necessary, because a SearchBar might access firstEntry()
     // while the scene is deleted. Maybe there is a better solution to
     // this problem, but I can't seem to find it.
     m_firstEntry = nullptr;
 
-    //disconnect from everything, no need to react on session status changes
-    //in the logout() when deleting the worksheet
-    disconnect(m_session, nullptr, nullptr, nullptr);
-
-    if (m_session && m_session->status() != Cantor::Session::Disable)
-        m_session->logout();
     if (m_session)
     {
         disconnect(m_session, nullptr, nullptr, nullptr);
@@ -129,6 +125,7 @@ Worksheet::~Worksheet()
             m_session->logout();
         m_session->deleteLater();
     }
+
     if (m_jupyterMetadata)
         delete m_jupyterMetadata;
 }
@@ -455,6 +452,9 @@ WorksheetView* Worksheet::worksheetView()
 
 void Worksheet::setModified()
 {
+    if (m_isClosing)
+        return;
+
     if (!m_isLoadingFromFile)
         emit modified();
 }

src/worksheet.h

@@ -378,6 +378,7 @@ class Worksheet : public QGraphicsScene
 
     bool m_isPrinting{false};
     bool m_isLoadingFromFile{false};
+    bool m_isClosing{false};
     bool m_readOnly{false};
 
     Type m_type = CantorWorksheet;