diff --git a/src/backends/R/rexpression.cpp b/src/backends/R/rexpression.cpp
index 3e55ed09..564187ce 100644
--- a/src/backends/R/rexpression.cpp
+++ b/src/backends/R/rexpression.cpp
@@ -1,160 +1,161 @@
 /*
     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 "rexpression.h"
 
 #include "textresult.h"
 #include "imageresult.h"
 #include "helpresult.h"
 #include "epsresult.h"
 #include "rsession.h"
 
 
 #include <QDebug>
 #include <KLocalizedString>
 #include <QMimeType>
 #include <QMimeDatabase>
 #include <QFile>
 #include <QStringList>
 #include <QTextDocument>
 
 RExpression::RExpression( Cantor::Session* session ) : Cantor::Expression(session)
 {
 
 }
 
 RExpression::~RExpression()
 {
 
 }
 
 void RExpression::evaluate()
 {
     if(command().startsWith(QLatin1Char('?')))
         m_isHelpRequest=true;
     else
         m_isHelpRequest=false;
 
     session()->enqueueExpression(this);
 }
 
 void RExpression::interrupt()
 {
     qDebug()<<"interrupting command";
-    if(status()==Cantor::Expression::Computing)
-        session()->interrupt();
     setStatus(Cantor::Expression::Interrupted);
 }
 
 void RExpression::finished(int returnCode, const QString& text)
 {
+    if (status() == Expression::Interrupted)
+        return;
+
     if(returnCode==RExpression::SuccessCode)
     {
         qDebug() << "text: " << text;
         setResult(new Cantor::TextResult(text));
         setStatus(Cantor::Expression::Done);
     }else if (returnCode==RExpression::ErrorCode)
     {
         qDebug() << "text: " << text;
         //setResult(new Cantor::TextResult(text));
         setErrorMessage(text);
         setStatus(Cantor::Expression::Error);
     }
 }
 
 void RExpression::evaluationStarted()
 {
     setStatus(Cantor::Expression::Computing);
 }
 
 void RExpression::addInformation(const QString& information)
 {
     static_cast<RSession*>(session())->sendInputToServer(information);
 }
 
 void RExpression::showFilesAsResult(const QStringList& files)
 {
     qDebug()<<"showing files: "<<files;
     foreach(const QString& file, files)
     {
         QMimeType type;
         QMimeDatabase db;
 
         type=db.mimeTypeForUrl(QUrl(file));
         qDebug()<<"MimeType: "<<type.name();
         if(type.inherits(QLatin1String("application/postscript")))
         {
             qDebug()<<"its PostScript";
             setResult(new Cantor::EpsResult(QUrl::fromLocalFile(file)));
         }
         else if(type.inherits(QLatin1String("text/plain"))
             || type.inherits(QLatin1String("application/x-extension-html")))
         {
             //Htmls are also plain texts, combining this in one
             const bool isHtml = type.inherits(QLatin1String("text/html"))
                 || type.inherits(QLatin1String("application/x-extension-html"));
             if(isHtml)
                 qDebug()<<"its a HTML document";
             else
                 qDebug()<<"its plain text";
 
             QFile f(file);
             if (!f.open(QIODevice::ReadOnly | QIODevice::Text))
             {
                 setResult(new Cantor::TextResult(i18n("Error opening file %1", file)));
                 setErrorMessage(i18n("Error opening file %1", file));
                 setStatus(Cantor::Expression::Error);
             }
             QString content=QTextStream(&f).readAll();
             if (!isHtml)
             {
                 //Escape whitespace
                 content.replace( QLatin1Char(' '), QLatin1String("&nbsp;"));
                 //replace appearing backspaces, as they mess the whole output up
                 content.remove(QRegExp(QLatin1String(".\b")));
             }
 
             qDebug()<<"content: "<<content;
             if(m_isHelpRequest)
                 setResult(new Cantor::HelpResult(content));
             else
                 setResult(new Cantor::TextResult(content));
 	    setStatus(Cantor::Expression::Done);
         }else if (type.name().contains(QLatin1String("image")))
         {
             setResult(new Cantor::ImageResult(QUrl::fromLocalFile(file)));
 	    setStatus(Cantor::Expression::Done);
         }
         else
         {
             // File has unsupported mime type, but we suspect, that it is text, so will open the file in Cantor script editor
             // Even if it don't text, the script editor can deals with it.
             setResult(new Cantor::TextResult(QLatin1String("")));
             setStatus(Cantor::Expression::Done);
             const QString& editor = QStandardPaths::findExecutable(QLatin1String("cantor_scripteditor"));
             int code = QProcess::execute(editor, QStringList(file));
             if (code == -2)
                 qDebug() << "failed to open the file " << file << " with the script editor '" << editor << "'";
             else if (code == -1)
                 qDebug() << "Cantor script editor crashed";
         }
     }
 }
 
diff --git a/src/backends/R/rsession.cpp b/src/backends/R/rsession.cpp
index 2489832f..a06ff512 100644
--- a/src/backends/R/rsession.cpp
+++ b/src/backends/R/rsession.cpp
@@ -1,198 +1,202 @@
 /*
     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>
     Copyright (C) 2018 Alexander Semke <alexander.semke@web.de>
  */
 
 #include "rsession.h"
 #include "rexpression.h"
 #include "rcompletionobject.h"
 #include "rhighlighter.h"
 #include <defaultvariablemodel.h>
 
 #include <QTimer>
 #include <QDebug>
 #include <KProcess>
 
 #ifndef Q_OS_WIN
 #include <signal.h>
 #endif
 
 RSession::RSession(Cantor::Backend* backend) : Session(backend), m_process(nullptr), m_rServer(nullptr), m_variableModel(new Cantor::DefaultVariableModel(this))
 {
 }
 
 RSession::~RSession()
 {
     if (m_process)
         m_process->terminate();
 }
 
 void RSession::login()
 {
     qDebug()<<"login";
     emit loginStarted();
 
     if(m_process)
         m_process->deleteLater();
 
     m_process = new QProcess(this);
     m_process->start(QStandardPaths::findExecutable(QLatin1String("cantor_rserver")));
     m_process->waitForStarted();
     m_process->waitForReadyRead();
     qDebug()<<m_process->readAllStandardOutput();
 
     m_rServer = new org::kde::Cantor::R(QString::fromLatin1("org.kde.Cantor.R-%1").arg(m_process->pid()),  QLatin1String("/"), QDBusConnection::sessionBus(), this);
 
     connect(m_rServer, SIGNAL(statusChanged(int)), this, SLOT(serverChangedStatus(int)));
     connect(m_rServer, SIGNAL(symbolList(const QStringList&, const QStringList&, const QStringList&)),this,SLOT(receiveSymbols(const QStringList&, const QStringList&, const QStringList&)));
 
     emit loginDone();
     qDebug()<<"login done";
 }
 
 void RSession::logout()
 {
     qDebug()<<"logout";
     m_process->terminate();
 }
 
 void RSession::interrupt()
 {
-    const int pid = m_process->pid();
-    qDebug()<<"interrupt" << pid;
-    if (pid)
+    if(expressionQueue().first())
     {
+        qDebug()<<"interrupting " << expressionQueue().first()->command();
+        if(m_process->state() != QProcess::NotRunning)
+        {
 #ifndef Q_OS_WIN
-        kill(pid, SIGINT);
+            const int pid=m_process->pid();
+            kill(pid, SIGINT);
 #else
-      //TODO: interrupt the process on windows
+            ; //TODO: interrupt the process on windows
 #endif
+        }
+        qDebug()<<"done interrupting";
+        expressionQueue().first()->interrupt();
     }
 
-    expressionQueue().removeFirst();
     changeStatus(Cantor::Session::Done);
 }
 
 Cantor::Expression* RSession::evaluateExpression(const QString& cmd, Cantor::Expression::FinishingBehavior behave)
 {
     qDebug()<<"evaluating: "<<cmd;
     RExpression* expr=new RExpression(this);
     expr->setFinishingBehavior(behave);
     expr->setCommand(cmd);
 
     expr->evaluate();
 
     changeStatus(Cantor::Session::Running);
 
     return expr;
 }
 
 Cantor::CompletionObject* RSession::completionFor(const QString& command, int index)
 {
     RCompletionObject *cmp=new RCompletionObject(command, index, this);
     connect(m_rServer,SIGNAL(completionFinished(const QString&,const QStringList&)),cmp,SLOT(receiveCompletions(const QString&,const QStringList&)));
     connect(cmp,SIGNAL(requestCompletion(const QString&)),m_rServer,SLOT(completeCommand(const QString&)));
     return cmp;
 }
 
 QSyntaxHighlighter* RSession::syntaxHighlighter(QObject* parent)
 {
     RHighlighter *h=new RHighlighter(parent);
     connect(h,SIGNAL(syntaxRegExps(QVector<QRegExp>&,QVector<QRegExp>&)),this,SLOT(fillSyntaxRegExps(QVector<QRegExp>&,QVector<QRegExp>&)));
     connect(this,SIGNAL(symbolsChanged()),h,SLOT(refreshSyntaxRegExps()));
     return h;
 }
 
 void RSession::fillSyntaxRegExps(QVector<QRegExp>& v, QVector<QRegExp>& f)
 {
     // WARNING: current implementation as-in-maxima is a performance hit
     // think about grouping expressions together or only fetching needed ones
     v.clear(); f.clear();
 
     foreach (const QString s, m_variables)
         if (!s.contains(QRegExp(QLatin1String("[^A-Za-z0-9_.]"))))
             v.append(QRegExp(QLatin1String("\\b")+s+QLatin1String("\\b")));
     foreach (const QString s, m_functions)
         if (!s.contains(QRegExp(QLatin1String("[^A-Za-z0-9_.]"))))
             f.append(QRegExp(QLatin1String("\\b")+s+QLatin1String("\\b")));
 }
 
 void RSession::receiveSymbols(const QStringList& vars, const QStringList& values, const QStringList & funcs)
 {
     m_variables = vars;
     for (int i = 0; i < vars.count(); i++)
         {
         m_variableModel->addVariable(vars[i], values[i]);
         }
     m_functions = funcs;
 
     emit symbolsChanged();
 }
 
 void RSession::serverChangedStatus(int status)
 {
     qDebug()<<"changed status to "<<status;
     if(status==0)
     {
         if(!expressionQueue().isEmpty())
         {
             RExpression* expr = static_cast<RExpression*>(expressionQueue().takeFirst());
             qDebug()<<"done running "<<expr<<" "<<expr->command();
         }
 
         if(expressionQueue().isEmpty())
             changeStatus(Cantor::Session::Done);
         else
             runFirstExpression();
     }
     else
         changeStatus(Cantor::Session::Running);
 }
 
 void RSession::runFirstExpression()
 {
     if (expressionQueue().isEmpty())
         return;
 
     disconnect(m_rServer,  SIGNAL(expressionFinished(int, const QString&)),  0,  0);
     disconnect(m_rServer, SIGNAL(inputRequested(const QString&)), 0, 0);
     disconnect(m_rServer, SIGNAL(showFilesNeeded(const QStringList&)), 0, 0);
     qDebug()<<"size: "<<expressionQueue().size();
     RExpression* expr = static_cast<RExpression*>(expressionQueue().first());
     qDebug()<<"running expression: "<<expr->command();
 
     connect(m_rServer, SIGNAL(expressionFinished(int,  const QString &)), expr, SLOT(finished(int, const QString&)));
     connect(m_rServer, SIGNAL(inputRequested(const QString&)), expr, SIGNAL(needsAdditionalInformation(const QString&)));
     connect(m_rServer, SIGNAL(showFilesNeeded(const QStringList&)), expr, SLOT(showFilesAsResult(const QStringList&)));
 
     m_rServer->runCommand(expr->command());
 }
 
 void RSession::sendInputToServer(const QString& input)
 {
     QString s=input;
     if(!input.endsWith(QLatin1Char('\n')))
         s+=QLatin1Char('\n');
     m_rServer->answerRequest(s);
 }
 
 QAbstractItemModel* RSession::variableModel()
 {
     return m_variableModel;
 }
diff --git a/src/backends/maxima/maximaexpression.cpp b/src/backends/maxima/maximaexpression.cpp
index 96774e22..e27d0f5c 100644
--- a/src/backends/maxima/maximaexpression.cpp
+++ b/src/backends/maxima/maximaexpression.cpp
@@ -1,768 +1,768 @@
 /*
     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) 2009-2012 Alexander Rieder <alexanderrieder@gmail.com>
  */
 
 #include "maximaexpression.h"
 
 #include <config-cantorlib.h>
 
 #include "maximasession.h"
 #include "textresult.h"
 #include "epsresult.h"
 #include "imageresult.h"
 #include "helpresult.h"
 #include "latexresult.h"
 #include "settings.h"
 
 #include <QDir>
 #include <QTemporaryFile>
 
 #include <KLocalizedString>
 #include <QDebug>
 #include <QTimer>
 #include <QRegExp>
 #include <QChar>
 #include <QUrl>
 
 MaximaExpression::MaximaExpression( Cantor::Session* session ) : Cantor::Expression(session),
     m_tempFile(nullptr),
     m_isHelpRequest(false),
     m_isPlot(false),
     m_gotErrorContent(false)
 {
 }
 
 void MaximaExpression::evaluate()
 {
     setStatus(Cantor::Expression::Computing);
 
     //until we get the real output Id from maxima, set it to invalid
     setId(-1);
 
     m_isHelpRequest=false;
     m_isPlot=false;
     m_gotErrorContent=false;
     if(m_tempFile)
         m_tempFile->deleteLater();
     m_tempFile=nullptr;
     //check if this is a ?command
     if(command().startsWith(QLatin1Char('?'))||command().startsWith(QLatin1String("describe("))||command().startsWith(QLatin1String("example(")))
         m_isHelpRequest=true;
 
     if(command().contains(QRegExp(QLatin1String("(?:plot2d|plot3d|contour_plot)\\s*\\([^\\)]"))) && MaximaSettings::self()->integratePlots() && !command().contains(QLatin1String("ps_file")))
     {
         m_isPlot=true;
 #ifdef WITH_EPS
         m_tempFile=new QTemporaryFile(QDir::tempPath() + QLatin1String("/cantor_maxima-XXXXXX.eps" ));
 #else
         m_tempFile=new QTemporaryFile(QDir::tempPath() + QLatin1String("/cantor_maxima-XXXXXX.png"));
 #endif
         m_tempFile->open();
 
         disconnect(&m_fileWatch, &KDirWatch::dirty, this, &MaximaExpression::imageChanged);
         m_fileWatch.addFile(m_tempFile->fileName());
         connect(&m_fileWatch, &KDirWatch::dirty, this, &MaximaExpression::imageChanged);
     }
 
     const QString& cmd=command();
 
     bool isComment = true;
     int commentLevel = 0;
     bool inString = false;
     for (int i = 0; i < cmd.size(); ++i) {
         if (cmd[i] == QLatin1Char('\\')) {
             ++i; // skip the next character
             if (commentLevel == 0 && !inString) {
                 isComment = false;
             }
         } else if (cmd[i] == QLatin1Char('"') && commentLevel == 0) {
             inString = !inString;
             isComment = false;
         } else if (cmd.mid(i,2) == QLatin1String("/*") && !inString) {
             ++commentLevel;
             ++i;
         } else if (cmd.mid(i,2) == QLatin1String("*/") && !inString) {
             if (commentLevel == 0) {
                 qDebug() << "Comments mismatched!";
                 setErrorMessage(i18n("Error: Too many */"));
                 setStatus(Cantor::Expression::Error);
                 return;
             }
             ++i;
             --commentLevel;
         } else if (isComment && commentLevel == 0 && !cmd[i].isSpace()) {
             isComment = false;
         }
     }
 
     if (commentLevel > 0) {
         qDebug() << "Comments mismatched!";
         setErrorMessage(i18n("Error: Too many /*"));
         setStatus(Cantor::Expression::Error);
         return;
     }
     if (inString) {
         qDebug() << "String not closed";
         setErrorMessage(i18n("Error: expected \" before ;"));
         setStatus(Cantor::Expression::Error);
         return;
     }
     if(isComment)
     {
         setStatus(Cantor::Expression::Done);
         return;
     }
 
     session()->enqueueExpression(this);
 }
 
 void MaximaExpression::interrupt()
 {
-    dynamic_cast<MaximaSession*>(session())->interrupt(this);
+    qDebug()<<"interrupting";
     setStatus(Cantor::Expression::Interrupted);
 }
 
 QString MaximaExpression::internalCommand()
 {
     QString cmd=command();
 
     if(m_isPlot)
     {
         if(!m_tempFile)
         {
             qDebug()<<"plotting without tempFile";
             return QString();
         }
         QString fileName = m_tempFile->fileName();
 
 #ifdef WITH_EPS
         const QString psParam=QLatin1String("[gnuplot_ps_term_command, \"set size 1.0,  1.0; set term postscript eps color solid \"]");
         const QString plotParameters = QLatin1String("[ps_file, \"")+ fileName+QLatin1String("\"],")+psParam;
 #else
         const QString plotParameters = QLatin1String("[gnuplot_term, \"png size 500,340\"], [gnuplot_out_file, \"")+fileName+QLatin1String("\"]");
 
 #endif
         cmd.replace(QRegExp(QLatin1String("((plot2d|plot3d|contour_plot)\\s*\\(.*)\\)([;\n]|$)")), QLatin1String("\\1, ")+plotParameters+QLatin1String(");"));
 
     }
 
     if (!cmd.endsWith(QLatin1Char('$')))
     {
         if (!cmd.endsWith(QLatin1String(";")))
             cmd+=QLatin1Char(';');
     }
 
     //replace all newlines with spaces, as maxima isn't sensitive about
     //whitespaces, and without newlines the whole command
     //is executed at once, without outputting an input
     //prompt after each line
     cmd.replace(QLatin1Char('\n'), QLatin1Char(' '));
 
     //lisp-quiet doesn't print a prompt after the command
     //is completed, which causes the parsing to hang.
     //replace the command with the non-quiet version
     cmd.replace(QRegExp(QLatin1String("^:lisp-quiet")), QLatin1String(":lisp"));
 
     return cmd;
 }
 
 void MaximaExpression::forceDone()
 {
     qDebug()<<"forcing Expression state to DONE";
     setResult(nullptr);
     setStatus(Cantor::Expression::Done);
 }
 
 void MaximaExpression::addInformation(const QString& information)
 {
     qDebug()<<"adding information";
     QString inf=information;
     if(!inf.endsWith(QLatin1Char(';')))
         inf+=QLatin1Char(';');
     Cantor::Expression::addInformation(inf);
 
     dynamic_cast<MaximaSession*>(session())->sendInputToProcess(inf+QLatin1Char('\n'));
 }
 
 
 //The maxima backend is modified, so that it outputs
 //xml-style tags around outputs, input prompts etc.
 //the following are some simple helper functions to faciliate parsing
 inline void skipWhitespaces(int* idx, const QString& txt)
 {
     for(;*idx < txt.size() && (txt[*idx]).isSpace();++(*idx));
 }
 
 QStringRef readXmlOpeningTag(int* idx, const QString& txt, bool* isComplete=nullptr)
 {
     qDebug()<<"trying to read an opening tag";
 
     if (*idx >= txt.size())
         return QStringRef();
 
     skipWhitespaces(idx, txt);
 
     if(isComplete)
         *isComplete=false;
 
     if(txt[*idx]!=QLatin1Char('<'))
     {
         qDebug()<<"This is NOT AN OPENING TAG."<<endl
                 <<"Dropping everything until next opening; This starts with a " <<txt[*idx];
         int newIdx=txt.indexOf(QLatin1Char('<'), *idx);
         if(newIdx==-1) //no more opening brackets in this string
         {
             return QStringRef();
         }else
         {
             (*idx)=newIdx+1;
         }
 
     }else
     {
         ++ (*idx);
     }
 
     int startIndex=*idx;
     int length=0;
     while(*idx<txt.size())
     {
         const QChar c=txt[*idx];
         ++(*idx);
 
         if(c==QLatin1Char('>'))
         {
             if(isComplete)
                 *isComplete=true;
             break;
         }else
             length++;
     }
 
     return QStringRef(&txt, startIndex, length);
 }
 
 QStringRef readXmlTagContent(int* idx, const QString& txt, const QStringRef& name, bool* isComplete=nullptr)
 {
     bool readingClosingTag=false;
     int contentStartIdx=*idx;
     int contentLength=0;
     int currentTagStartIdx=-1;
     int currentTagLength=0;
 
     if(isComplete)
         *isComplete=false;
 
     while(*idx<txt.size())
     {
         const QChar c=txt[*idx];
 
         if(c==QLatin1Char('/')&&(*idx)>0&&txt[(*idx)-1]==QLatin1Char('<'))
         {
             //remove the opening <
             contentLength--;
             currentTagStartIdx=*idx+1;
             currentTagLength=0;
             readingClosingTag=true;
         }
         else if(readingClosingTag)
         {
             if(c==QLatin1Char('>'))
             {
                 const QStringRef currentTagName(&txt, currentTagStartIdx, currentTagLength);
 
                 if(currentTagName==name)
                 {
                     //eat up the closing >
                     ++(*idx);
                     if(isComplete)
                         (*isComplete)=true;
                     break;
                 }
 
                 readingClosingTag=false;
             }else
                 currentTagLength++;
         }
         else
             contentLength++;
 
 
         ++(*idx);
 
     }
 
     if(contentStartIdx+contentLength>txt.size())
     {
         qDebug()<<"something is wrong with the content-length "<<contentStartIdx+contentLength<<
             " vs: "<<txt.size();
     }
     return QStringRef(&txt,contentStartIdx, contentLength);
 }
 
 bool MaximaExpression::parseOutputOld(QString& out)
 {
     enum ParserStatus{ReadingOpeningTag, ReadingClosingTag, ReadingText};
     int idx=0;
     int numResults=0;
     QString textBuffer;
     QString latexBuffer;
     QString errorBuffer;
 
     Cantor::Result* result=nullptr;
     while(idx<out.size())
     {
         skipWhitespaces(&idx, out);
 
         //first read the part not enclosed in tags. it most likely belongs to an error message
         int idx1=out.indexOf(QLatin1String("<cantor-prompt>"), idx);
         int idx2=out.indexOf(QLatin1String("<cantor-result>"), idx);
 
         idx1=(idx1==-1) ? out.size():idx1;
         idx2=(idx2==-1) ? out.size():idx2;
         int newIdx=qMin(idx1, idx2);
 
         if(newIdx>idx)
         {
             const QString& err=out.mid(idx, newIdx-idx);
             if(!err.isEmpty())
                 m_gotErrorContent=true;
             errorBuffer+=err;
             qDebug()<<"the unmatched part of the output is: "<<err;
             idx=newIdx;
         }
 
         const QStringRef& tag=readXmlOpeningTag(&idx, out);
 
         if(tag==QLatin1String("cantor-result"))
         {
             qDebug()<<"got a result";
 
             if(numResults>0)
             {
                 textBuffer.append(QLatin1String("\n"));
                 latexBuffer.append(QLatin1String("\n"));
             }
 
             result=parseResult(&idx, out, textBuffer, latexBuffer);
             numResults++;
 
             qDebug()<<"got "<<numResults<<"th result.";
 
         }else if (tag==QLatin1String("cantor-prompt"))
         {
             qDebug()<<"i got a prompt: "<<idx;
 
             skipWhitespaces(&idx, out);
 
             //We got a child tag
             if(out[idx]==QLatin1Char('<'))
             {
                 const QStringRef& childTag=readXmlOpeningTag(&idx, out);
                 qDebug()<<"got an information request!"<<childTag;
 
                 QStringRef text;
                 QStringRef latex;
                 while(idx<out.size())
                 {
                     const QStringRef& type=readXmlOpeningTag(&idx, out);
                     qDebug()<<"its a "<<type;
                     if(type==QLatin1String("/cantor-result"))
                         break;
                     const QStringRef& content=readXmlTagContent(&idx, out, type);
 
                     if(type==QLatin1String("cantor-text"))
                         text=content;
                     else if(type==QLatin1String("cantor-latex"))
                         latex=content;
 
                     qDebug()<<"content: "<<content;
                 }
 
                 bool isComplete;
                 //readup the rest of the element and discard it
                 readXmlTagContent(&idx, out,tag, &isComplete);
 
                 if(!isComplete)
                     return false;
 
                 //send out the information request
                 emit needsAdditionalInformation(text.toString());
 
                 out=out.mid(idx);
                 idx=0;
 
                 return true;
 
             }else //got a regular prompt. Just read it all
             {
                 bool isComplete;
                 readXmlTagContent(&idx, out, tag, &isComplete);
 
                 if(!isComplete)
                     return false;
 
                 m_errorBuffer+=errorBuffer;
                 if(!m_errorBuffer.trimmed().isEmpty())
                 {
                     if(command().startsWith(QLatin1String(":lisp"))||command().startsWith(QLatin1String(":lisp-quiet")))
                     {
                         if(result)
                         {
                             if(result->type()==Cantor::TextResult::Type)
                                 m_errorBuffer.prepend(dynamic_cast<Cantor::TextResult*>(result)->plain()+QLatin1String("\n"));
                             else if(result->type()==Cantor::LatexResult::Type)
                                 m_errorBuffer.prepend(dynamic_cast<Cantor::LatexResult*>(result)->plain()+QLatin1String("\n"));
                         }
 
                         Cantor::TextResult* result=new Cantor::TextResult(m_errorBuffer);
                         setResult(result);
                         setStatus(Cantor::Expression::Done);
                     }else
                     if(m_isHelpRequest) //Help Messages are also provided in the errorBuffer.
                     {
                         Cantor::HelpResult* result=new Cantor::HelpResult(m_errorBuffer);
                         setResult(result);
 
                         setStatus(Cantor::Expression::Done);
                     }else
                     {
                         if(result)
                         {
                             qDebug()<<"result: "<<result->toHtml();
                             if(result->type()==Cantor::TextResult::Type)
                                 m_errorBuffer.prepend(dynamic_cast<Cantor::TextResult*>(result)->plain()+QLatin1String("\n"));
                             else if(result->type()==Cantor::LatexResult::Type)
                                 m_errorBuffer.prepend(dynamic_cast<Cantor::LatexResult*>(result)->plain()+QLatin1String("\n"));
                         }
 
                         qDebug()<<"errorBuffer: "<<m_errorBuffer;
 
 
                         setErrorMessage(m_errorBuffer.trimmed());
                         if(m_gotErrorContent)
                             setStatus(Cantor::Expression::Error);
                         else
                             setStatus(Cantor::Expression::Done);
                     }
                 }
                 else
                 {
                     //if we got an error message, but also a result, lets just+
                     //assume that it was just a warning, as obviously something worked
                     if(errorMessage().isEmpty()||result!=nullptr)
                     {
                         setResult(result);
                         setStatus(Cantor::Expression::Done);
                     }
                     else
                     {
                         if(!result)
                             setStatus(Cantor::Expression::Error);
 
                     }
                 }
 
                 out=out.mid(idx);
                 idx=0;
 
                 return true;
             }
         }else
         {
             qDebug()<<"unknown tag"<<tag;
         }
     }
 
     //show partial result
     setResult(result);
     return false;
 }
 
 Cantor::Result* MaximaExpression::parseResult(int* idx, QString& out,
                                               QString& textBuffer, QString& latexBuffer)
 {
     bool isLatexComplete=false;
     QString latex;
     QString text;
 
     while(*idx<out.size())
     {
         bool isComplete;
         const QStringRef& type=readXmlOpeningTag(idx, out);
 
         if(type==QLatin1String("/cantor-result"))
             break;
 
         const QStringRef& content=readXmlTagContent(idx, out, type, &isComplete);
 
         if(type==QLatin1String("cantor-text"))
             text=content.toString().trimmed();
         else if(type==QLatin1String("cantor-latex"))
         {
             isLatexComplete=isComplete;
             latex=content.toString().trimmed();
         }
     }
 
     QRegExp outputPromptRegexp=QRegExp(QLatin1Char('^')+MaximaSession::MaximaOutputPrompt.pattern());
     int idxOfPrompt=outputPromptRegexp.indexIn(text);
     text.remove(idxOfPrompt, outputPromptRegexp.matchedLength());
 
     //find the number if this output in the MaximaOutputPrompt
     QString prompt=outputPromptRegexp.cap(0).trimmed();
     bool ok;
     QString idString=prompt.mid(3, prompt.length()-4);
     int id=idString.toInt(&ok);
     if(ok)
         setId(id);
     else
         setId(-1);
     qDebug()<<"prompt: "<<prompt<<" id: "<<id;
 
     if(m_tempFile)
     {
         QTimer::singleShot(500, this, SLOT(imageChanged()));
     }
 
     Cantor::TextResult* result=nullptr;
 
     //if this is not the first result, prepend the results
     //found in the earlier tags.
     textBuffer.append(text);
 
     //if the <latex> element wasn't read completely, there
     //is no point in trying to render it. Use text for
     //incomplete results.
     if(!isLatexComplete
        ||(latexBuffer.trimmed().isEmpty()&&latex.isEmpty())
        ||m_isHelpRequest||isInternal())
     {
         qDebug()<<"using text";
         result=new Cantor::TextResult(textBuffer);
     }else
     {
         qDebug()<<"using latex";
         //strip away the latex code for the label.
         //it is contained in an \mbox{} call
         int i;
         int pcount=0;
         for(i=latex.indexOf(QLatin1String("\\mbox{"))+5;i<latex.size();i++)
         {
             if(latex[i]==QLatin1Char('{'))
                 pcount++;
             else if(latex[i]==QLatin1Char('}'))
                 pcount--;
 
             if(pcount==0)
                 break;
         }
 
         latex=latex.mid(i+1);
 
         //no need to render empty latex.
         if(latexBuffer.trimmed().isEmpty()&&latex.trimmed().isEmpty())
         {
             if(m_isPlot)
                 result=new Cantor::TextResult(i18n("Waiting for Image..."));
             else
                 result=nullptr;
         }else
         {
             latex.prepend(QLatin1String("\\begin{eqnarray*}\n"));
             latex.append(QLatin1String("\n\\end{eqnarray*}"));
             latexBuffer.append(latex);
             result=new Cantor::TextResult(latexBuffer, textBuffer);
             result->setFormat(Cantor::TextResult::LatexFormat);
         }
     }
 
 
     return result;
 }
 
 
 /*!
     example output for the simple expression '5+5':
     latex mode - "<cantor-result><cantor-text>\n(%o1) 10\n</cantor-text><cantor-latex>\\mbox{\\tt\\red(\\mathrm{\\%o1}) \\black}10</cantor-latex></cantor-result>\n<cantor-prompt>(%i2) </cantor-prompt>\n"
     text mode  - "<cantor-result><cantor-text>\n(%o1) 10\n</cantor-text></cantor-result>\n<cantor-prompt>(%i2) </cantor-prompt>\n"
  */
 bool MaximaExpression::parseOutput(QString& out)
 {
     clearResult();
 
     const int promptStart = out.indexOf(QLatin1String("<cantor-prompt>"));
     const int promptEnd = out.indexOf(QLatin1String("</cantor-prompt>"));
     const QString prompt = out.mid(promptStart + 15, promptEnd - promptStart - 15).simplified();
 
     //check whether the result is part of the promt - this is the case when additional input is required from the user
     if (prompt.contains(QLatin1String("<cantor-result>")))
     {
         //text part of the output
         const int textContentStart = prompt.indexOf(QLatin1String("<cantor-text>"));
         const int textContentEnd = prompt.indexOf(QLatin1String("</cantor-text>"));
         QString textContent = prompt.mid(textContentStart + 13, textContentEnd - textContentStart - 13).trimmed();
 
         qDebug()<<"asking for additional input for " << textContent;
         emit needsAdditionalInformation(textContent);
         return true;
     }
 
     qDebug()<<"new input label: " << prompt;
 
     //parse the results
     int resultStart = out.indexOf(QLatin1String("<cantor-result>"));
     while (resultStart != -1)
     {
         int resultEnd = out.indexOf(QLatin1String("</cantor-result>"), resultStart + 15);
         const QString resultContent = out.mid(resultStart + 15, resultEnd - resultStart - 15);
         parseResult(resultContent);
 
         //search for the next openning <cantor-result> tag after the current closing </cantor-result> tag
         resultStart = out.indexOf(QLatin1String("<cantor-result>"), resultEnd + 16);
     }
 
     //parse the error message, the part outside of the <cantor*> tags
     int lastResultEnd = out.lastIndexOf(QLatin1String("</cantor-result>"));
     if (lastResultEnd != -1)
         lastResultEnd += 16;
     else
         lastResultEnd = 0;
 
     QString errorContent = out.mid(lastResultEnd, promptStart - lastResultEnd).trimmed();
     if (errorContent.isEmpty())
     {
         setStatus(Cantor::Expression::Done);
     }
     else
     {
         qDebug() << "error content: " << errorContent;
         if(m_isHelpRequest) //help messages are also part of the error output
         {
             Cantor::HelpResult* result = new Cantor::HelpResult(errorContent);
             addResult(result);
             setStatus(Cantor::Expression::Done);
         }
         else
         {
             errorContent = errorContent.replace(QLatin1String("\n\n"), QLatin1String("<br>"));
             errorContent = errorContent.replace(QLatin1String("\n"), QLatin1String("<br>"));
             setErrorMessage(errorContent);
             setStatus(Cantor::Expression::Error);
         }
     }
 
     return true;
 }
 
 void MaximaExpression::parseResult(const QString& resultContent)
 {
     qDebug()<<"result content: " << resultContent;
 
     //text part of the output
     const int textContentStart = resultContent.indexOf(QLatin1String("<cantor-text>"));
     const int textContentEnd = resultContent.indexOf(QLatin1String("</cantor-text>"));
     QString textContent = resultContent.mid(textContentStart + 13, textContentEnd - textContentStart - 13).trimmed();
     qDebug()<<"text content: " << textContent;
 
     //output label can be a part of the text content -> determine it
     const QRegExp regex = QRegExp(MaximaSession::MaximaOutputPrompt.pattern());
     const int index = regex.indexIn(textContent);
     QString outputLabel;
     if (index != -1) // No match, so output don't contain output label
         outputLabel = textContent.mid(index, regex.matchedLength()).trimmed();
     qDebug()<<"output label: " << outputLabel;
 
     //remove the output label from the text content
     textContent = textContent.remove(outputLabel).trimmed();
 
     //determine the actual result
     Cantor::TextResult* result = nullptr;
 
     const int latexContentStart = resultContent.indexOf(QLatin1String("<cantor-latex>"));
     if (latexContentStart != -1)
     {
         //latex output is available
         const int latexContentEnd = resultContent.indexOf(QLatin1String("</cantor-latex>"));
         QString latexContent = resultContent.mid(latexContentStart + 14, latexContentEnd - latexContentStart - 14).trimmed();
         qDebug()<<"latex content: " << latexContent;
 
         //replace the \mbox{} environment, if available, by the eqnarray environment
         if (latexContent.indexOf(QLatin1String("\\mbox{")) != -1)
         {
             int i;
             int pcount=0;
             for(i = latexContent.indexOf(QLatin1String("\\mbox{"))+5; i < latexContent.size(); ++i)
             {
                 if(latexContent[i]==QLatin1Char('{'))
                     pcount++;
                 else if(latexContent[i]==QLatin1Char('}'))
                     pcount--;
 
                 if(pcount==0)
                     break;
             }
 
             QString modifiedLatexContent = latexContent.mid(i+1);
             if(modifiedLatexContent.trimmed().isEmpty())
             {
                 //empty content in the \mbox{} environment (e.g. for print() outputs), use the latex string outside of the \mbox{} environment
                 modifiedLatexContent = latexContent.left(latexContent.indexOf(QLatin1String("\\mbox{")));
             }
 
             modifiedLatexContent.prepend(QLatin1String("\\begin{eqnarray*}"));
             modifiedLatexContent.append(QLatin1String("\\end{eqnarray*}"));
             result = new Cantor::TextResult(modifiedLatexContent, textContent);
             qDebug()<<"modified latex content: " << modifiedLatexContent;
         }
         else
         {
             //no \mbox{} available, use what we've got.
             result = new Cantor::TextResult(latexContent, textContent);
         }
 
         result->setFormat(Cantor::TextResult::LatexFormat);
     }
     else
     {
         //no latex output is availabe, the actual result is part of the textContent string
         result = new Cantor::TextResult(textContent);
     }
 
     addResult(result);
 }
 
 void MaximaExpression::parseError(const QString& out)
 {
     m_errorBuffer.append(out);
 }
 
 void MaximaExpression::imageChanged()
 {
     qDebug()<<"the temp image has changed";
     if(m_tempFile->size()>0)
     {
 #ifdef WITH_EPS
         setResult( new Cantor::EpsResult( QUrl::fromLocalFile(m_tempFile->fileName()) ) );
 #else
         setResult( new Cantor::ImageResult( QUrl::fromLocalFile(m_tempFile->fileName()) ) );
 #endif
         setStatus(Cantor::Expression::Done);
     }
 }
diff --git a/src/backends/maxima/maximasession.cpp b/src/backends/maxima/maximasession.cpp
index 9614b5be..ba48b8e6 100644
--- a/src/backends/maxima/maximasession.cpp
+++ b/src/backends/maxima/maximasession.cpp
@@ -1,347 +1,341 @@
 /*
     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) 2009-2012 Alexander Rieder <alexanderrieder@gmail.com>
     Copyright (C) 2017-2018 Alexander Semke (alexander.semke@web.de)
  */
 
 #include "maximasession.h"
 #include "maximaexpression.h"
 #include "maximacompletionobject.h"
 #include "maximasyntaxhelpobject.h"
 #include "maximahighlighter.h"
 #include "maximavariablemodel.h"
 #include "result.h"
 #include "settings.h"
 
 #include <QDebug>
 #include <QProcess>
 #include <QTimer>
 
 #include <KMessageBox>
 #include <KLocalizedString>
 
 #ifndef Q_OS_WIN
 #include <signal.h>
 #endif
 
 
 //NOTE: the \\s in the expressions is needed, because Maxima seems to sometimes insert newlines/spaces between the letters
 //maybe this is caused by some behaviour if the Prompt is split into multiple "readStdout" calls
 //the Expressions are encapsulated in () to allow capturing for the text
 const QRegExp MaximaSession::MaximaOutputPrompt=QRegExp(QLatin1String("(\\(\\s*%\\s*o\\s*[0-9\\s]*\\))")); //Text, maxima outputs, before any output
 
 
 MaximaSession::MaximaSession( Cantor::Backend* backend ) : Session(backend),
     m_process(nullptr),
     m_variableModel(new MaximaVariableModel(this)),
     m_justRestarted(false)
 {
 }
 
 void MaximaSession::login()
 {
     qDebug()<<"login";
 
     if (m_process)
         return; //TODO: why do we call login() again?!?
 
     emit loginStarted();
     QStringList arguments;
     arguments << QLatin1String("--quiet"); //Suppress Maxima start-up message
     const QString initFile = QStandardPaths::locate(QStandardPaths::GenericDataLocation, QLatin1String("cantor/maximabackend/cantor-initmaxima.lisp"));
     arguments << QLatin1String("--init-lisp=") + initFile; //Set the name of the Lisp initialization file
 
     m_process = new QProcess(this);
     m_process->start(MaximaSettings::self()->path().toLocalFile(), arguments);
     m_process->waitForStarted();
     m_process->waitForReadyRead();
     qDebug()<<m_process->readAllStandardOutput();
 
     connect(m_process, SIGNAL(finished(int, QProcess::ExitStatus)), this, SLOT(restartMaxima()));
     connect(m_process, SIGNAL(readyReadStandardOutput()), this, SLOT(readStdOut()));
     connect(m_process, SIGNAL(readyReadStandardError()), this, SLOT(readStdErr()));
     connect(m_process, SIGNAL(error(QProcess::ProcessError)), this, SLOT(reportProcessError(QProcess::ProcessError)));
 
     //TODO
 //     if(!MaximaSettings::self()->autorunScripts().isEmpty()){
 //         QString autorunScripts = MaximaSettings::self()->autorunScripts().join(QLatin1String("\n"));
 //         evaluateExpression(autorunScripts, MaximaExpression::DeleteOnFinish);
 // //         runFirstExpression();
 //     }
 
     emit loginDone();
     qDebug()<<"login done";
 }
 
 void MaximaSession::logout()
 {
     qDebug()<<"logout";
 
     if(!m_process)
         return;
 
     disconnect(m_process, 0, this, 0);
 
 //     if(status()==Cantor::Session::Running)
         //TODO: terminate the running expressions first
 
     write(QLatin1String("quit();\n"));
     qDebug()<<"waiting for maxima to finish";
     m_process->waitForFinished();
     qDebug()<<"maxima exit finished";
 
     if(m_process->state() != QProcess::NotRunning)
     {
         m_process->kill();
         qDebug()<<"maxima still running, process kill enforced";
     }
 
     expressionQueue().clear();
     delete m_process;
     m_process = nullptr;
 
     qDebug()<<"logout done";
 }
 
 Cantor::Expression* MaximaSession::evaluateExpression(const QString& cmd, Cantor::Expression::FinishingBehavior behave)
 {
     qDebug() << "evaluating: " << cmd;
     MaximaExpression* expr = new MaximaExpression(this);
     expr->setFinishingBehavior(behave);
     expr->setCommand(cmd);
     expr->evaluate();
 
     return expr;
 }
 
 void MaximaSession::readStdErr()
 {
    qDebug()<<"reading stdErr";
    if (!m_process)
        return;
    QString out=QLatin1String(m_process->readAllStandardError());
 
    if(expressionQueue().size()>0)
    {
        MaximaExpression* expr = static_cast<MaximaExpression*>(expressionQueue().first());
        expr->parseError(out);
    }
 }
 
 void MaximaSession::readStdOut()
 {
     QString out = QLatin1String(m_process->readAllStandardOutput());
     m_cache += out;
 
     //collect the multi-line output until Maxima has finished the calculation and returns a new promt
     if ( !out.contains(QLatin1String("</cantor-prompt>")) )
         return;
 
     if(expressionQueue().isEmpty())
     {
         //queue is empty, interrupt was called, nothing to do here
         qDebug()<<m_cache;
         m_cache.clear();
         return;
     }
 
     MaximaExpression* expr = static_cast<MaximaExpression*>(expressionQueue().first());
     if (!expr)
         return; //should never happen
 
     qDebug()<<"output: " << m_cache;
     expr->parseOutput(m_cache);
     m_cache.clear();
 }
 
 void MaximaSession::killLabels()
 {
     Cantor::Expression* e=evaluateExpression(QLatin1String("kill(labels);"), Cantor::Expression::DeleteOnFinish);
     e->setInternal(true);
     //TODO: what for? connect(e, SIGNAL(statusChanged(Cantor::Expression::Status)), this, SIGNAL(ready()));
 }
 
 void MaximaSession::reportProcessError(QProcess::ProcessError e)
 {
     qDebug()<<"process error"<<e;
     if(e==QProcess::FailedToStart)
     {
         changeStatus(Cantor::Session::Done);
         emit error(i18n("Failed to start Maxima"));
     }
 }
 
 void MaximaSession::currentExpressionChangedStatus(Cantor::Expression::Status status)
 {
     Cantor::Expression* expression = expressionQueue().first();
     qDebug() << "expression status changed: command = " << expression->command() << ", status = " << status;
 
     if(status!=Cantor::Expression::Computing) //The session is ready for the next command
     {
         qDebug()<<"################################## EXPRESSION END ###############################################";
         disconnect(expression, SIGNAL(statusChanged(Cantor::Expression::Status)),
                    this, SLOT(currentExpressionChangedStatus(Cantor::Expression::Status)));
 
         expressionQueue().removeFirst();
         if(expressionQueue().isEmpty())
         {
             //if we are done with all the commands in the queue,
             //use the opportunity to update the variablemodel (if the last command wasn't already an update, as infinite loops aren't fun)
             QRegExp exp=QRegExp(QRegExp::escape(MaximaVariableModel::inspectCommand).arg(QLatin1String("(values|functions)")));
             QRegExp exp2=QRegExp(QRegExp::escape(MaximaVariableModel::variableInspectCommand).arg(QLatin1String("(values|functions)")));
 
             if(MaximaSettings::variableManagement()&&!exp.exactMatch(expression->command())&&!exp2.exactMatch(expression->command()))
             {
                 m_variableModel->checkForNewFunctions();
                 m_variableModel->checkForNewVariables();
             }else
             {
                 changeStatus(Cantor::Session::Done);
             }
 
         }else
         {
             runFirstExpression();
         }
     }
 }
 
 void MaximaSession::runFirstExpression()
 {
     qDebug()<<"running next expression";
     if (!m_process)
         return;
 
     if(!expressionQueue().isEmpty())
     {
         MaximaExpression* expr = static_cast<MaximaExpression*>(expressionQueue().first());
         QString command=expr->internalCommand();
         connect(expr, SIGNAL(statusChanged(Cantor::Expression::Status)), this, SLOT(currentExpressionChangedStatus(Cantor::Expression::Status)));
 
         if(command.isEmpty())
         {
             qDebug()<<"empty command";
             expr->forceDone();
         }
         else
         {
             m_cache.clear();
             write(command + QLatin1Char('\n'));
         }
     }
 }
 
 void MaximaSession::interrupt()
 {
-    if(!expressionQueue().isEmpty())
-        expressionQueue().first()->interrupt();
-
-    expressionQueue().clear();
-    changeStatus(Cantor::Session::Done);
-}
-
-void MaximaSession::interrupt(MaximaExpression* expr)
-{
-    if(expr==expressionQueue().first())
+    if(expressionQueue().first())
     {
-        qDebug()<<"interrupting " << expr->command();
-        disconnect(expr, nullptr, this, nullptr);
+        qDebug()<<"interrupting " << expressionQueue().first()->command();
+        if(m_process->state() != QProcess::NotRunning)
+        {
 #ifndef Q_OS_WIN
-        const int pid=m_process->pid();
-        kill(pid, SIGINT);
+            const int pid=m_process->pid();
+            kill(pid, SIGINT);
 #else
-      //TODO: interrupt the process on windows
+            ; //TODO: interrupt the process on windows
 #endif
+        }
         qDebug()<<"done interrupting";
-    }else
-    {
-        expressionQueue().removeAll(expr);
+        expressionQueue().first()->interrupt();
     }
+
+    changeStatus(Cantor::Session::Done);
+    m_cache.clear();
 }
 
 void MaximaSession::sendInputToProcess(const QString& input)
 {
     write(input);
 }
 
 void MaximaSession::restartMaxima()
 {
     qDebug()<<"restarting maxima cooldown: "<<m_justRestarted;
 
     if(!m_justRestarted)
     {
         emit error(i18n("Maxima crashed. restarting..."));
         //remove the command that caused maxima to crash (to avoid infinite loops)
         if(!expressionQueue().isEmpty())
             expressionQueue().removeFirst();
 
         m_justRestarted=true;
         QTimer::singleShot(1000, this, SLOT(restartsCooledDown()));
 
         disconnect(m_process, SIGNAL(finished(int, QProcess::ExitStatus)), this, SLOT(restartMaxima()));
         login();
     }else
     {
         if(!expressionQueue().isEmpty())
             expressionQueue().removeFirst();
         KMessageBox::error(nullptr, i18n("Maxima crashed twice within a short time. Stopping to try starting"), i18n("Error - Cantor"));
     }
 }
 
 void MaximaSession::restartsCooledDown()
 {
     qDebug()<<"maxima restart cooldown";
     m_justRestarted=false;
 }
 
 void MaximaSession::setTypesettingEnabled(bool enable)
 {
     //we use the lisp command to set the variable, as those commands
     //don't mess with the labels and history
     const QString& val=QLatin1String((enable==true ? "t":"nil"));
     Cantor::Expression* exp=evaluateExpression(QString::fromLatin1(":lisp(setf $display2d %1)").arg(val), Cantor::Expression::DeleteOnFinish);
     exp->setInternal(true);
 
     Cantor::Session::setTypesettingEnabled(enable);
 }
 
 Cantor::CompletionObject* MaximaSession::completionFor(const QString& command, int index)
 {
     return new MaximaCompletionObject(command, index, this);
 }
 
 Cantor::SyntaxHelpObject* MaximaSession::syntaxHelpFor(const QString& command)
 {
     return new MaximaSyntaxHelpObject(command, this);
 }
 
 QSyntaxHighlighter* MaximaSession::syntaxHighlighter(QObject* parent)
 {
     return new MaximaHighlighter(parent, this);
 }
 
 QAbstractItemModel* MaximaSession::variableModel()
 {
     return m_variableModel;
 }
 
 void MaximaSession::write(const QString& exp) {
     qDebug()<<"################################## EXPRESSION START ###############################################";
     qDebug()<<"sending expression to maxima process: " << exp;
     m_process->write(exp.toUtf8());
 }
diff --git a/src/backends/maxima/maximasession.h b/src/backends/maxima/maximasession.h
index 3cd49f58..1fa5f87d 100644
--- a/src/backends/maxima/maximasession.h
+++ b/src/backends/maxima/maximasession.h
@@ -1,84 +1,83 @@
 /*
     Tims 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) 2009-2012 Alexander Rieder <alexanderrieder@gmail.com>
  */
 
 #ifndef _MAXIMASESSION_H
 #define _MAXIMASESSION_H
 
 #include "session.h"
 #include "expression.h"
 #include <QProcess>
 
 class MaximaExpression;
 class MaximaVariableModel;
 
 #ifdef Q_OS_WIN
   class KProcess;
 #else
   class KPtyProcess;
 #endif
 
 class MaximaSession : public Cantor::Session
 {
   Q_OBJECT
   public:
     static const QRegExp MaximaOutputPrompt;
 
     MaximaSession( Cantor::Backend* backend);
 
     void login() Q_DECL_OVERRIDE;
     void logout() Q_DECL_OVERRIDE;
 
     Cantor::Expression* evaluateExpression(const QString& command, Cantor::Expression::FinishingBehavior behave) Q_DECL_OVERRIDE;
 
     void interrupt() Q_DECL_OVERRIDE;
-    void interrupt(MaximaExpression* expr);
     void sendInputToProcess(const QString& input);
 
     void setTypesettingEnabled(bool enable) Q_DECL_OVERRIDE;
 
     Cantor::CompletionObject* completionFor(const QString& command, int index=-1) Q_DECL_OVERRIDE;
     Cantor::SyntaxHelpObject* syntaxHelpFor(const QString& command) Q_DECL_OVERRIDE;
     QSyntaxHighlighter* syntaxHighlighter(QObject* parent) Q_DECL_OVERRIDE;
     QAbstractItemModel* variableModel() Q_DECL_OVERRIDE;
     void runFirstExpression() override;
 
   public Q_SLOTS:
     void readStdOut();
     void readStdErr();
 
   private Q_SLOTS:
     void currentExpressionChangedStatus(Cantor::Expression::Status status);
     void restartMaxima();
     void restartsCooledDown();
 
     void killLabels();
 
     void reportProcessError(QProcess::ProcessError error);
 
   private:
     void write(const QString&);
 
     QProcess* m_process;
     QString m_cache;
     MaximaVariableModel* m_variableModel;
     bool m_justRestarted;
 };
 
 #endif /* _MAXIMASESSION_H */
diff --git a/src/backends/octave/octavesession.cpp b/src/backends/octave/octavesession.cpp
index f1f963e2..024a6d8d 100644
--- a/src/backends/octave/octavesession.cpp
+++ b/src/backends/octave/octavesession.cpp
@@ -1,336 +1,338 @@
 /*
     Copyright (C) 2010 Miha Čančula <miha.cancula@gmail.com>
 
     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.
 */
 
 #include "octavesession.h"
 #include "octaveexpression.h"
 #include "octavecompletionobject.h"
 #include "octavesyntaxhelpobject.h"
 #include "result.h"
 #include "textresult.h"
 
 #include "settings.h"
 #include "octave-backend-config.h"
 
 #include <KProcess>
 #include <KDirWatch>
 
 #include <QTimer>
 #include <QFile>
 #include "octavehighlighter.h"
 #include <settings.h>
 
 #ifndef Q_OS_WIN
 #include <signal.h>
 #endif
 
 #include <defaultvariablemodel.h>
 
 OctaveSession::OctaveSession ( Cantor::Backend* backend ) : Session ( backend ),
 m_process(nullptr),
 m_watch(nullptr),
 m_variableModel(new Cantor::DefaultVariableModel(this))
 {
     qDebug() << octaveScriptInstallDir;
 }
 
 OctaveSession::~OctaveSession()
 {
 
 }
 
 void OctaveSession::login()
 {
     qDebug() << "login";
     emit loginStarted();
 
     m_process = new KProcess ( this );
     QStringList args;
     args << QLatin1String("--silent");
     args << QLatin1String("--interactive");
     args << QLatin1String("--persist");
 
     // Add the cantor script directory to search path
     args << QLatin1String("--eval");
     args << QString::fromLatin1("addpath %1;").arg(octaveScriptInstallDir);
 
     if (OctaveSettings::integratePlots())
     {
         // Do not show the popup when plotting, rather only print to a file
         args << QLatin1String("--eval");
         args << QLatin1String("graphics_toolkit gnuplot;");
         args << QLatin1String("--eval");
         args << QLatin1String("set (0, \"defaultfigurevisible\",\"off\");");
     }
     else
     {
         args << QLatin1String("--eval");
         args << QLatin1String("set (0, \"defaultfigurevisible\",\"on\");");
     }
 
     // Do not show extra text in help commands
     args << QLatin1String("--eval");
     args << QLatin1String("suppress_verbose_help_message(1);");
 
     // Print the temp dir, used for plot files
     args << QLatin1String("--eval");
     args << QLatin1String("____TMP_DIR____ = tempdir");
 
     if (OctaveSettings::integratePlots())
     {
         m_watch = new KDirWatch(this);
         m_watch->setObjectName(QLatin1String("OctaveDirWatch"));
         connect (m_watch, SIGNAL(dirty(QString)), SLOT(plotFileChanged(QString)) );
     }
 
     // connect the signal and slots prior to staring octave to make sure we handle the very first output
     // in parserOutput() to determine the temp folder and the format of the promt
     connect ( m_process, SIGNAL ( readyReadStandardOutput() ), SLOT ( readOutput() ) );
     connect ( m_process, SIGNAL ( readyReadStandardError() ), SLOT ( readError() ) );
     connect ( m_process, SIGNAL ( error ( QProcess::ProcessError ) ), SLOT ( processError() ) );
 
     m_process->setProgram ( OctaveSettings::path().toLocalFile(), args );
     qDebug() << "starting " << m_process->program();
     m_process->setOutputChannelMode ( KProcess::SeparateChannels );
     m_process->start();
     m_process->waitForStarted();
     m_process->waitForReadyRead();
 
     if(!OctaveSettings::self()->autorunScripts().isEmpty()){
         QString autorunScripts = OctaveSettings::self()->autorunScripts().join(QLatin1String("\n"));
 
         evaluateExpression(autorunScripts, OctaveExpression::DeleteOnFinish);
     }
 
     emit loginDone();
     qDebug()<<"login done";
 }
 
 void OctaveSession::logout()
 {
     qDebug()<<"logout";
 
     if(!m_process)
         return;
 
     disconnect(m_process, 0, this, 0);
 
 //     if(status()==Cantor::Session::Running)
         //TODO: terminate the running expressions first
 
     m_process->write("exit\n");
     qDebug()<<"waiting for octave to finish";
     m_process->waitForFinished();
     qDebug()<<"octave exit finished";
 
     if(m_process->state() != QProcess::NotRunning)
     {
         m_process->kill();
         qDebug()<<"octave still running, process kill enforced";
     }
 
     expressionQueue().clear();
     delete m_process;
     m_process = nullptr;
 
     m_prompt = QRegExp();
     m_tempDir.clear();
 
     qDebug()<<"logout done";
 }
 
 void OctaveSession::interrupt()
 {
-    qDebug() << "interrupt";
-    if (expressionQueue().first())
+    if(expressionQueue().first())
     {
-        expressionQueue().first()->interrupt();
-    }
-    expressionQueue().clear();
-    qDebug() << "Sending SIGINT to Octave";
-    // Some commands, like `quit()`, potentially could finish octave process
-    // So, avoiding crash, have make check before call kill, that the process still exist
-    if(m_process->state() != QProcess::NotRunning)
+        qDebug()<<"interrupting " << expressionQueue().first()->command();
+        if(m_process->state() != QProcess::NotRunning)
+        {
 #ifndef Q_OS_WIN
-        kill(m_process->pid(), SIGINT);
+            const int pid=m_process->pid();
+            kill(pid, SIGINT);
 #else
-        ; //TODO: interrupt the process on windows
+            ; //TODO: interrupt the process on windows
 #endif
+        }
+        qDebug()<<"done interrupting";
+        expressionQueue().first()->interrupt();
+    }
+
+    changeStatus(Cantor::Session::Done);
 }
 
 void OctaveSession::processError()
 {
     qDebug() << "processError";
     emit error(m_process->errorString());
 }
 
 Cantor::Expression* OctaveSession::evaluateExpression ( const QString& command, Cantor::Expression::FinishingBehavior finishingBehavior )
 {
     qDebug() << "evaluating: " << command;
     OctaveExpression* expression = new OctaveExpression ( this );
     expression->setCommand ( command );
     expression->setFinishingBehavior ( finishingBehavior );
     expression->evaluate();
 
     return expression;
 }
 
 void OctaveSession::runFirstExpression()
 {
     OctaveExpression* expression = static_cast<OctaveExpression*>(expressionQueue().first());
     connect(expression, SIGNAL(statusChanged(Cantor::Expression::Status)), this, SLOT(currentExpressionStatusChanged(Cantor::Expression::Status)));
     QString command = expression->command();
     command.replace(QLatin1Char('\n'), QLatin1Char(','));
     command += QLatin1Char('\n');
     m_process->write ( command.toLocal8Bit() );
 }
 
 void OctaveSession::readError()
 {
     qDebug() << "readError";
     QString error = QString::fromLocal8Bit(m_process->readAllStandardError());
     if (expressionQueue().first() && !error.isEmpty())
     {
         static_cast<OctaveExpression*>(expressionQueue().first())->parseError(error);
     }
 }
 
 void OctaveSession::readOutput()
 {
     qDebug() << "readOutput";
     while (m_process->bytesAvailable() > 0)
     {
         if (m_tempDir.isEmpty() && !m_process->canReadLine())
         {
             qDebug() << "Waiting";
             // Wait for the full line containing octave's tempDir
             return;
         }
         QString line = QString::fromLocal8Bit(m_process->readLine());
         qDebug()<<"start parsing " << "  " << line;
         if (!expressionQueue().first() || m_prompt.isEmpty())
         {
             // no expression is available, we're parsing the first output of octave after the start
             // -> determine the location of the temporary folder and the format of octave's promt
             if (m_prompt.isEmpty() && line.contains(QLatin1String(":1>")))
             {
                 qDebug() << "Found Octave prompt:" << line;
                 line.replace(QLatin1String(":1"), QLatin1String(":[0-9]+"));
                 m_prompt.setPattern(line);
             }
             else if (line.contains(QLatin1String("____TMP_DIR____")))
             {
                 m_tempDir = line;
                 m_tempDir.remove(0,18);
                 m_tempDir.chop(1); // isolate the tempDir's location
                 qDebug() << "Got temporary file dir:" << m_tempDir;
                 if (m_watch)
                 {
                     m_watch->addDir(m_tempDir, KDirWatch::WatchFiles);
                 }
             }
         }
         else if (line.contains(m_prompt))
         {
             // Check for errors before finalizing the expression
             // this makes sure that all errors are caught
             readError();
             // Get command before finalize, because after finalizing the expression will be dequeued
             const QString& command = expressionQueue().first()->command();
             static_cast<OctaveExpression*>(expressionQueue().first())->finalize();
             if (command.contains(QLatin1String(" = ")))
             {
                 emit variablesChanged();
             }
             if (command.contains(QLatin1String("function ")))
             {
                 emit functionsChanged();
             }
         }
         else
         {
             // Avoid many calls to setResult if a lot of output came at the same time
             while (m_process->canReadLine())
             {
                 line += QString::fromLocal8Bit(m_process->readLine());
             }
             static_cast<OctaveExpression*>(expressionQueue().first())->parseOutput(line);
 
         }
     }
 }
 
 void OctaveSession::currentExpressionStatusChanged(Cantor::Expression::Status status)
 {
     qDebug() << "currentExpressionStatusChanged";
     switch (status)
     {
     case Cantor::Expression::Done:
     case Cantor::Expression::Error:
         changeStatus(Done);
         expressionQueue().removeFirst();
         if (!expressionQueue().isEmpty())
         {
             runFirstExpression();
         }
         break;
     default:
         break;
     }
 }
 
 void OctaveSession::plotFileChanged(const QString& filename)
 {
     if (!QFile::exists(filename) || !filename.split(QLatin1Char('/')).last().contains(QLatin1String("c-ob-")))
     {
         return;
     }
     if (expressionQueue().first())
     {
         static_cast<OctaveExpression*>(expressionQueue().first())->parsePlotFile(filename);
     }
 }
 
 Cantor::CompletionObject* OctaveSession::completionFor ( const QString& cmd, int index )
 {
     return new OctaveCompletionObject ( cmd, index, this );
 }
 
 Cantor::SyntaxHelpObject* OctaveSession::syntaxHelpFor ( const QString& cmd )
 {
     return new OctaveSyntaxHelpObject ( cmd, this );
 }
 
 QSyntaxHighlighter* OctaveSession::syntaxHighlighter ( QObject* parent )
 {
     OctaveHighlighter* highlighter = new OctaveHighlighter ( parent, this );
     connect ( this, SIGNAL(functionsChanged()), highlighter, SLOT(updateFunctions()) );
     connect ( this, SIGNAL(variablesChanged()), highlighter, SLOT(updateVariables()) );
     return highlighter;
 }
 
 QAbstractItemModel* OctaveSession::variableModel()
 {
     return m_variableModel;
 }
 
 
 void OctaveSession::runSpecificCommands()
 {
     m_process->write("figure(1,'visible','off')");
 }
diff --git a/src/backends/sage/sagesession.cpp b/src/backends/sage/sagesession.cpp
index f23914ad..5990d1f1 100644
--- a/src/backends/sage/sagesession.cpp
+++ b/src/backends/sage/sagesession.cpp
@@ -1,473 +1,491 @@
 /*
     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 "sagesession.h"
 #include "sageexpression.h"
 #include "sagecompletionobject.h"
 #include "sagehighlighter.h"
 
 #include <QDebug>
 #include <QRegularExpression>
 #include <KPtyProcess>
 #include <KPtyDevice>
 #include <KLocalizedString>
 #include <KMessageBox>
 #include "settings.h"
 
+#ifndef Q_OS_WIN
+#include <signal.h>
+#endif
+
 const QByteArray SageSession::SagePrompt="sage: "; //Text, sage outputs after each command
 const QByteArray SageSession::SageAlternativePrompt="....: "; //Text, sage outputs when it expects further input
 
 //some commands that are run after login
 static QByteArray initCmd="os.environ['PAGER'] = 'cat'                     \n "\
                            "sage.misc.pager.EMBEDDED_MODE = True           \n "\
                            "sage.misc.viewer.BROWSER=''                    \n "\
                            "sage.misc.viewer.viewer.png_viewer('false')         \n" \
                            "sage.plot.plot3d.base.SHOW_DEFAULTS['viewer'] = 'tachyon' \n"\
                            "sage.misc.latex.EMBEDDED_MODE = True           \n "\
                            "os.environ['PAGER'] = 'cat'                    \n "\
                            "%colors nocolor                                \n "\
                            "print '____TMP_DIR____', sage.misc.misc.SAGE_TMP\n";
 
 static QByteArray newInitCmd=
     "__CANTOR_IPYTHON_SHELL__=get_ipython()   \n "\
     "__CANTOR_IPYTHON_SHELL__.autoindent=False\n ";
 
 static QByteArray legacyInitCmd=
     "__CANTOR_IPYTHON_SHELL__=__IPYTHON__   \n "  \
     "__CANTOR_IPYTHON_SHELL__.autoindent=False\n ";
 
 static QByteArray endOfInitMarker="print '____END_OF_INIT____'\n ";
 
 
 
 SageSession::VersionInfo::VersionInfo(int major, int minor)
 {
     m_major=major;
     m_minor=minor;
 }
 
 int SageSession::VersionInfo::majorVersion() const
 {
     return m_major;
 }
 
 int SageSession::VersionInfo::minorVersion() const
 {
     return m_minor;
 }
 
 bool SageSession::VersionInfo::operator==(VersionInfo other) const
 {
     return m_major==other.m_major&&m_minor==other.m_minor;
 }
 
 bool SageSession::VersionInfo::operator<(VersionInfo other) const
 {
     return (m_major!= -1 && other.m_major==-1) ||
         ( ((m_major!=-1 && other.m_major!=-1) || (m_major==other.m_major && m_major==-1) ) && ( m_major<other.m_major||(m_major==other.m_major&&m_minor<other.m_minor) ) );
 }
 
 bool SageSession::VersionInfo::operator<=(VersionInfo other) const
 {
     return (*this < other)||(*this == other);
 }
 
 bool SageSession::VersionInfo::operator>(SageSession::VersionInfo other) const
 {
     return !( (*this <= other ));
 }
 
 bool SageSession::VersionInfo::operator>=(SageSession::VersionInfo other) const
 {
     return !( *this < other);
 }
 
 SageSession::SageSession(Cantor::Backend* backend) : Session(backend)
 {
     m_isInitialized=false;
     m_haveSentInitCmd=false;
     connect( &m_dirWatch, SIGNAL( created( const QString& ) ), this, SLOT( fileCreated( const QString& ) ) );
 }
 
 SageSession::~SageSession()
 {
 }
 
 void SageSession::login()
 {
     qDebug()<<"login";
     emit loginStarted();
 
     m_process=new KPtyProcess(this);
     updateSageVersion();
     const QString& sageExecFile = SageSettings::self()->path().toLocalFile();
     if (m_sageVersion >= SageSession::VersionInfo(8, 4))
         m_process->setProgram(sageExecFile, QStringList() << QLatin1String("--simple-prompt"));
     else
         {
         const QString& sageStartScript = QStandardPaths::locate(QStandardPaths::GenericDataLocation, QLatin1String("cantor/sagebackend/cantor-execsage"));
         m_process->setProgram(sageStartScript, QStringList(sageExecFile));
         }
 
     m_process->setOutputChannelMode(KProcess::SeparateChannels);
     m_process->setPtyChannels(KPtyProcess::AllChannels);
     m_process->pty()->setEcho(false);
 
     connect(m_process->pty(), SIGNAL(readyRead()), this, SLOT(readStdOut()));
     connect(m_process, SIGNAL(readyReadStandardError()), this, SLOT(readStdErr()));
     connect(m_process, SIGNAL(finished ( int,  QProcess::ExitStatus )), this, SLOT(processFinished(int, QProcess::ExitStatus)));
     connect(m_process, SIGNAL(error(QProcess::ProcessError)), this, SLOT(reportProcessError(QProcess::ProcessError)));
     m_process->start();
     m_process->waitForStarted();
 
     m_process->pty()->write(initCmd);
 
     if(!SageSettings::self()->autorunScripts().isEmpty()){
         QString autorunScripts = SageSettings::self()->autorunScripts().join(QLatin1String("\n"));
         evaluateExpression(autorunScripts, SageExpression::DeleteOnFinish);
     }
 
     emit loginDone();
 }
 
 void SageSession::logout()
 {
     qDebug()<<"logout";
 
     disconnect(m_process, SIGNAL(finished ( int,  QProcess::ExitStatus )), this, SLOT(processFinished(int, QProcess::ExitStatus)));
     m_process->pty()->write("exit\n");
 
     m_process->kill();
     //Run sage-cleaner to kill all the orphans
     KProcess::startDetached(SageSettings::self()->path().toLocalFile(),QStringList()<<QLatin1String("-cleaner"));
 
     expressionQueue().clear();
 }
 
 Cantor::Expression* SageSession::evaluateExpression(const QString& cmd, Cantor::Expression::FinishingBehavior behave)
 {
     qDebug()<<"evaluating: "<<cmd;
     SageExpression* expr=new SageExpression(this);
     expr->setFinishingBehavior(behave);
     expr->setCommand(cmd);
     expr->evaluate();
 
     return expr;
 }
 
 void SageSession::readStdOut()
 {
     m_outputCache.append(QString::fromUtf8(m_process->pty()->readAll()));
     qDebug()<<"out: "<<m_outputCache;
 
     if ( m_outputCache.contains( QLatin1String("___TMP_DIR___") ) )
     {
         int index=m_outputCache.indexOf(QLatin1String("___TMP_DIR___") )+14;
         int endIndex=m_outputCache.indexOf(QLatin1String("\n"), index);
 
         if(endIndex==-1)
             m_tmpPath=m_outputCache.mid( index ).trimmed();
         else
             m_tmpPath=m_outputCache.mid( index, endIndex-index ).trimmed();
 
         qDebug()<<"tmp path: "<<m_tmpPath;
 
         m_dirWatch.addDir( m_tmpPath, KDirWatch::WatchFiles );
     }
 
     if(!m_isInitialized)
     {
         if(updateSageVersion())
         {
             // After the update ipython5 somewhere around Sage 7.6, Cantor stopped working with Sage.
             // To fix this, we start Sage via a help wrapper that makes ipythong using simple prompt.
             // This method works starting with Sage 8.1"
             // Versions lower than 8.1 are not supported because of https://github.com/ipython/ipython/issues/9816
             if(m_sageVersion <= SageSession::VersionInfo(8, 0) && m_sageVersion >= SageSession::VersionInfo(7,4))
             {
                 const QString message = i18n(
                     "Sage version %1.%2 is unsupported. Please update your installation "\
                     "to the supported versions to make it work with Cantor.", m_sageVersion.majorVersion(), m_sageVersion.minorVersion());
                 KMessageBox::error(nullptr, message, i18n("Cantor"));
                 interrupt();
                 logout();
             }
             else if(m_sageVersion<=SageSession::VersionInfo(5, 7))
             {
                 qDebug()<<"using an old version of sage: "<<m_sageVersion.majorVersion()<<"."<<m_sageVersion.minorVersion()<<". Using the old init command";
                 if(!m_haveSentInitCmd)
                 {
                     m_process->pty()->write(legacyInitCmd);
                     defineCustomFunctions();
                     m_process->pty()->write(endOfInitMarker);
                     m_haveSentInitCmd=true;
                 }
 
             }
             else
             {
                 qDebug()<<"using the current set of commands";
 
                 if(!m_haveSentInitCmd)
                 {
                     m_process->pty()->write(newInitCmd);
                     defineCustomFunctions();
                     m_process->pty()->write(endOfInitMarker);
                     m_haveSentInitCmd=true;
                 }
             }
         }
     }
 
 
     int indexOfEOI=m_outputCache.indexOf(QLatin1String("____END_OF_INIT____"));
     if(indexOfEOI!=-1&&m_outputCache.indexOf(QLatin1String(SagePrompt), indexOfEOI)!=-1)
     {
         qDebug()<<"initialized";
         //out.remove("____END_OF_INIT____");
         //out.remove(SagePrompt);
         m_isInitialized=true;
         m_waitingForPrompt=false;
         runFirstExpression();
         changeStatus(Cantor::Session::Done);
         m_outputCache.clear();
     }
 
     //If we are waiting for another prompt, drop every output
     //until a prompt is found
     if(m_isInitialized&&m_waitingForPrompt)
     {
         qDebug()<<"waiting for prompt";
         if(m_outputCache.contains(QLatin1String(SagePrompt)))
             m_waitingForPrompt=false;
 
         m_outputCache.clear();
         return;
     }
 
     if(m_isInitialized&&!expressionQueue().isEmpty())
     {
         SageExpression* expr = static_cast<SageExpression*>(expressionQueue().first());
         expr->parseOutput(m_outputCache);
         m_outputCache.clear();
     }
 }
 
 void SageSession::readStdErr()
 {
     qDebug()<<"reading stdErr";
     QString out=QLatin1String(m_process->readAllStandardError());
     qDebug()<<"err: "<<out;
     if (!expressionQueue().isEmpty())
     {
         SageExpression* expr = static_cast<SageExpression*>(expressionQueue().first());
         expr->parseError(out);
     }
 }
 
 void SageSession::currentExpressionChangedStatus(Cantor::Expression::Status status)
 {
     if(status!=Cantor::Expression::Computing) //The session is ready for the next command
     {
         SageExpression* expr = static_cast<SageExpression*>(expressionQueue().takeFirst());
         disconnect(expr, nullptr, this, nullptr);
         if(expressionQueue().isEmpty())
             changeStatus(Cantor::Session::Done);
         runFirstExpression();
     }
 
 }
 
 void SageSession::processFinished(int exitCode, QProcess::ExitStatus exitStatus)
 {
     Q_UNUSED(exitCode);
     if(exitStatus==QProcess::CrashExit)
     {
         if(!expressionQueue().isEmpty())
         {
             static_cast<SageExpression*>(expressionQueue().last())
                 ->onProcessError(i18n("The Sage process crashed while evaluating this expression"));
         }else
         {
             //We don't have an actual command. it crashed for some other reason, just show a plain error message box
             KMessageBox::error(nullptr, i18n("The Sage process crashed"), i18n("Cantor"));
         }
     }else
     {
         if(!expressionQueue().isEmpty())
         {
             static_cast<SageExpression*>(expressionQueue().last())
                 ->onProcessError(i18n("The Sage process exited while evaluating this expression"));
         }else
         {
             //We don't have an actual command. it crashed for some other reason, just show a plain error message box
             KMessageBox::error(nullptr, i18n("The Sage process exited"), i18n("Cantor"));
         }
     }
 }
 
 void SageSession::reportProcessError(QProcess::ProcessError e)
 {
     if(e==QProcess::FailedToStart)
     {
         changeStatus(Cantor::Session::Done);
         emit error(i18n("Failed to start Sage"));
     }
 }
 
 void SageSession::runFirstExpression()
 {
     if(!expressionQueue().isEmpty()&&m_isInitialized)
     {
         SageExpression* expr = static_cast<SageExpression*>(expressionQueue().first());
         connect(expr, SIGNAL(statusChanged(Cantor::Expression::Status)), this, SLOT(currentExpressionChangedStatus(Cantor::Expression::Status)));
         QString command=expr->command();
         if(command.endsWith(QLatin1Char('?')) && !command.endsWith(QLatin1String("??")))
             command=QLatin1String("help(")+command.left(command.size()-1)+QLatin1Char(')');
         if(command.startsWith(QLatin1Char('?')))
             command=QLatin1String("help(")+command.mid(1)+QLatin1Char(')');
 
         qDebug()<<"writing "<<command<<" to the process";
         m_process->pty()->write(QString(command+QLatin1String("\n\n")).toUtf8());
     }
 }
 
 void SageSession::interrupt()
 {
-    if(!expressionQueue().isEmpty())
+    if(expressionQueue().first())
+    {
+        qDebug()<<"interrupting " << expressionQueue().first()->command();
+        if(m_process->state() != QProcess::NotRunning)
+        {
+#ifndef Q_OS_WIN
+            const int pid=m_process->pid();
+            kill(pid, SIGINT);
+#else
+            ; //TODO: interrupt the process on windows
+#endif
+        }
+        qDebug()<<"done interrupting";
         expressionQueue().first()->interrupt();
-    expressionQueue().clear();
+    }
+
     changeStatus(Cantor::Session::Done);
+    m_outputCache.clear();
 }
 
 void SageSession::sendSignalToProcess(int signal)
 {
     qDebug()<<"sending signal....."<<signal;
     //Sage spawns several child-processes. the one we are interested in is called sage-ipython.
     //But to determine which ipython process is the one belonging to this session, we search
     //for a bash process which is child of this sessions sage process, and only kill the
     //ipython process which is child of the bash process
     // the tree looks like: m_sageprocess->bash->sage-ipython
     QString cmd=QString::fromLatin1("pkill -%1 -f -P `pgrep  -P %2 bash` .*sage-ipython.*").arg(signal).arg(m_process->pid());
     KProcess proc(this);
     proc.setShellCommand(cmd);
     proc.execute();
 }
 
 void SageSession::sendInputToProcess(const QString& input)
 {
     m_process->pty()->write(input.toUtf8());
 }
 
 void SageSession::waitForNextPrompt()
 {
     m_waitingForPrompt=true;
 }
 
 void SageSession::fileCreated( const QString& path )
 {
     qDebug()<<"got a file "<<path;
     SageExpression* expr = static_cast<SageExpression*>(expressionQueue().first());
     if ( expr )
         expr->addFileResult( path );
 }
 
 void SageSession::setTypesettingEnabled(bool enable)
 {
     Cantor::Session::setTypesettingEnabled(enable);
 
     // We have problems with Sage latex output (generates invalid code sometimes), so disable sage
     // latex output until this not be solved. Users can enable sage latex by hands using %display
     // sage magic.
 
     //tell the sage server to enable/disable pretty_print
     //const QString cmd=QLatin1String("__cantor_enable_typesetting(%1)");
     //evaluateExpression(cmd.arg(enable ? QLatin1String("true"):QLatin1String("false")), Cantor::Expression::DeleteOnFinish);
 }
 
 void SageSession::setWorksheetPath(const QString& path)
 {
     //save the path to the worksheet as variable "__file__"
     //this variable is usually set by the "os" package when running a script
     //but when it is run in an interpreter (like sage server) it is not set
     const QString cmd = QLatin1String("__file__ = '%1'");
     evaluateExpression(cmd.arg(path), Cantor::Expression::DeleteOnFinish);
 }
 
 Cantor::CompletionObject* SageSession::completionFor(const QString& command, int index)
 {
     return new SageCompletionObject(command, index, this);
 }
 
 QSyntaxHighlighter* SageSession::syntaxHighlighter(QObject* parent)
 {
     return new SageHighlighter(parent);
 }
 
 SageSession::VersionInfo SageSession::sageVersion()
 {
     return m_sageVersion;
 }
 
 void SageSession::defineCustomFunctions()
 {
     //typesetting
     QString cmd=QLatin1String("def __cantor_enable_typesetting(enable):\n");
     if(m_sageVersion<VersionInfo(5, 7))
     {
         //the _ and __IP.outputcache() are needed to keep the
         // _ operator working. in modern versions of sage the __IP variable
         //has been removed
         cmd+=QLatin1String("\t sage.misc.latex.pretty_print_default(enable);_;__IP.outputcache() \n\n");
     }else if (m_sageVersion > VersionInfo(5, 7) && m_sageVersion< VersionInfo(5, 12))
     {
         cmd+=QLatin1String("\t sage.misc.latex.pretty_print_default(enable)\n\n");
     }else
     {
         cmd+=QLatin1String("\t if(enable==true):\n "\
              "\t \t %display typeset \n"\
              "\t else: \n" \
              "\t \t %display simple \n\n");
     }
 
     sendInputToProcess(cmd);
 }
 
 bool SageSession::updateSageVersion()
 {
     QProcess get_sage_version;
     get_sage_version.setProgram(SageSettings::self()->path().toLocalFile());
     get_sage_version.setArguments(QStringList()<<QLatin1String("-v"));
     get_sage_version.start();
     get_sage_version.waitForFinished(-1);
     QString versionString = QString::fromLocal8Bit(get_sage_version.readLine());
     QRegularExpression versionExp(QLatin1String("(\\d+)\\.(\\d+)"));
     QRegularExpressionMatch version = versionExp.match(versionString);
     qDebug()<<"found version: " << version.capturedTexts();
     if(version.isValid())
     {
         int major=version.capturedTexts()[1].toInt();
         int minor=version.capturedTexts()[2].toInt();
         m_sageVersion=SageSession::VersionInfo(major, minor);
         return true;
     }
     else
         return false;
 }