diff --git a/GUI/Views/FitWidgets/FitParameterWidget.cpp b/GUI/Views/FitWidgets/FitParameterWidget.cpp
index eeaba7c33fbf880fabc27fec7d2ca8909d22a6f9..030ab36a7a9ab702b0638bc7bf35419675a8bc18 100644
--- a/GUI/Views/FitWidgets/FitParameterWidget.cpp
+++ b/GUI/Views/FitWidgets/FitParameterWidget.cpp
@@ -75,22 +75,20 @@ FitParameterWidget::FitParameterWidget(QWidget* parent)
 
 void FitParameterWidget::setParameterTuningWidget(ParameterTuningWidget* tuningWidget)
 {
-    if (tuningWidget == m_tuningWidget) {
+    if (tuningWidget == m_tuningWidget)
         return;
 
-    } else {
-        if (m_tuningWidget)
-            disconnect(m_tuningWidget, &ParameterTuningWidget::itemContextMenuRequest, this,
-                       &FitParameterWidget::onTuningWidgetContextMenu);
+    if (m_tuningWidget)
+        disconnect(m_tuningWidget, &ParameterTuningWidget::itemContextMenuRequest, this,
+                   &FitParameterWidget::onTuningWidgetContextMenu);
 
-        m_tuningWidget = tuningWidget;
-        if (!m_tuningWidget)
-            return;
+    m_tuningWidget = tuningWidget;
+    if (!m_tuningWidget)
+        return;
 
-        connect(m_tuningWidget, &ParameterTuningWidget::itemContextMenuRequest, this,
-                &FitParameterWidget::onTuningWidgetContextMenu, Qt::UniqueConnection);
-        connect(m_tuningWidget, &QObject::destroyed, [this] { m_tuningWidget = nullptr; });
-    }
+    connect(m_tuningWidget, &ParameterTuningWidget::itemContextMenuRequest, this,
+            &FitParameterWidget::onTuningWidgetContextMenu, Qt::UniqueConnection);
+    connect(m_tuningWidget, &QObject::destroyed, [this] { m_tuningWidget = nullptr; });
 }
 
 // QSize FitParameterWidget::sizeHint() const
diff --git a/GUI/Views/FitWidgets/FitWorkerLauncher.cpp b/GUI/Views/FitWidgets/FitWorkerLauncher.cpp
index 9f9e95be1b51bacd4f11504d821f235f724e704a..31abed06d6e653ccd2bb1d33c99ea9f98d8438d5 100644
--- a/GUI/Views/FitWidgets/FitWorkerLauncher.cpp
+++ b/GUI/Views/FitWidgets/FitWorkerLauncher.cpp
@@ -50,7 +50,7 @@ void FitWorkerLauncher::runFitting(std::shared_ptr<FitObjectiveBuilder> suite)
 
 //! Returns duration of fit in msec.
 
-int FitWorkerLauncher::getDuration()
+int FitWorkerLauncher::getDuration() const
 {
     return m_duration;
 }
diff --git a/GUI/Views/FitWidgets/FitWorkerLauncher.h b/GUI/Views/FitWidgets/FitWorkerLauncher.h
index 68edbc7f904af033bb29ddb689d72cd92829896b..752f4df5cdf2b52f0d93777870ef9b74b234c029 100644
--- a/GUI/Views/FitWidgets/FitWorkerLauncher.h
+++ b/GUI/Views/FitWidgets/FitWorkerLauncher.h
@@ -29,7 +29,7 @@ public:
 
     void runFitting(std::shared_ptr<FitObjectiveBuilder> suite);
 
-    int getDuration();
+    int getDuration() const;
 
 public slots:
     void interruptFitting();
diff --git a/GUI/Views/FitWidgets/ParameterTuningDelegate.cpp b/GUI/Views/FitWidgets/ParameterTuningDelegate.cpp
index 8bce41f5f41eeede6260492e3674e71fabcb54a8..6e619371bed2b98d721c8a06f7e7eecd8502ee00 100644
--- a/GUI/Views/FitWidgets/ParameterTuningDelegate.cpp
+++ b/GUI/Views/FitWidgets/ParameterTuningDelegate.cpp
@@ -74,7 +74,7 @@ int ParameterTuningDelegate::TuningData::value_to_slider(double value)
     return static_cast<int>(result);
 }
 
-double ParameterTuningDelegate::TuningData::slider_to_value(int slider)
+double ParameterTuningDelegate::TuningData::slider_to_value(int slider) const
 {
     return m_rmin + (slider - m_smin) * (m_rmax - m_rmin) / (m_smax - m_smin);
 }
@@ -131,82 +131,81 @@ QWidget* ParameterTuningDelegate::createEditor(QWidget* parent, const QStyleOpti
     if (m_isReadOnly)
         return nullptr;
 
-    if (index.column() == m_valueColumn) {
-        if (index.parent().isValid() == false)
-            return nullptr;
-
-        QVariant data = index.model()->data(index, Qt::EditRole);
-        if (!data.isValid())
-            return nullptr;
-
-        m_currentItem = static_cast<ParameterItem*>(
-            ParameterTuningModel::toSourceIndex(index).internalPointer());
-        if (!m_currentItem)
-            return nullptr;
-
-        double value = data.toDouble();
-        RealLimits limits = m_currentItem->linkedItem()->limits();
-        m_tuning_info.setItemLimits(limits);
-        m_tuning_info.value_to_slider(value);
-
-        // initializing value box
-        m_valueBox = new ScientificSpinBox();
-        m_valueBox->setKeyboardTracking(false);
-        m_valueBox->setFixedWidth(105);
-        m_valueBox->setDecimals(m_currentItem->linkedItem()->decimals());
-        m_valueBox->setSingleStep(m_tuning_info.step());
-
-        if (limits.hasLowerLimit()) {
-            m_valueBox->setMinimum(limits.lowerLimit());
-        } else {
-            m_valueBox->setMinimum(minimum_doublespin_value);
-        }
+    if (index.column() != m_valueColumn)
+        return QItemDelegate::createEditor(parent, option, index);
 
-        if (limits.hasUpperLimit()) {
-            m_valueBox->setMaximum(limits.upperLimit());
-        } else {
-            m_valueBox->setMaximum(maximum_doublespin_value);
-        }
+    if (index.parent().isValid() == false)
+        return nullptr;
+
+    QVariant data = index.model()->data(index, Qt::EditRole);
+    if (!data.isValid())
+        return nullptr;
 
-        m_valueBox->setValue(value);
-        connect(m_valueBox, &ScientificSpinBox::valueChanged, this,
-                &ParameterTuningDelegate::editorValueChanged);
-
-        // initializing slider
-        m_slider = new QSlider(Qt::Horizontal);
-        m_slider->setFocusPolicy(Qt::StrongFocus);
-        m_slider->setTickPosition(QSlider::NoTicks);
-        m_slider->setTickInterval(1);
-        m_slider->setSingleStep(1);
-        m_slider->setRange(m_tuning_info.m_smin, m_tuning_info.m_smax);
-
-        updateSlider(value);
-
-        m_contentWidget = new QWidget(parent);
-        m_contentLayout = new QHBoxLayout(parent);
-        m_contentLayout->setMargin(0);
-        m_contentLayout->setSpacing(0);
-        m_contentLayout->addWidget(m_valueBox);
-        m_contentLayout->addWidget(m_slider);
-
-        // FIXME there is an issue with time of life of editor .vs. item
-        //        m_currentItem->mapper()->setOnValueChange(
-        //                      [this](){
-        //            if(m_valueBox && m_currentItem)
-        //              m_valueBox->setValue(m_currentItem->value().toDouble());
-        //        }, this);
-
-        //        m_currentItem->mapper()->setOnItemDestroy(
-        //                    [this](SessionItem *) {
-        //            m_currentItem = 0;
-        //        }, this);
-
-        m_contentWidget->setLayout(m_contentLayout);
-
-        return m_contentWidget;
+    m_currentItem = static_cast<ParameterItem*>(
+        ParameterTuningModel::toSourceIndex(index).internalPointer());
+    if (!m_currentItem)
+        return nullptr;
+
+    double value = data.toDouble();
+    RealLimits limits = m_currentItem->linkedItem()->limits();
+    m_tuning_info.setItemLimits(limits);
+    m_tuning_info.value_to_slider(value);
+
+    // initializing value box
+    m_valueBox = new ScientificSpinBox();
+    m_valueBox->setKeyboardTracking(false);
+    m_valueBox->setFixedWidth(105);
+    m_valueBox->setDecimals(m_currentItem->linkedItem()->decimals());
+    m_valueBox->setSingleStep(m_tuning_info.step());
+
+    if (limits.hasLowerLimit()) {
+        m_valueBox->setMinimum(limits.lowerLimit());
     } else {
-        return QItemDelegate::createEditor(parent, option, index);
+        m_valueBox->setMinimum(minimum_doublespin_value);
     }
+
+    if (limits.hasUpperLimit()) {
+        m_valueBox->setMaximum(limits.upperLimit());
+    } else {
+        m_valueBox->setMaximum(maximum_doublespin_value);
+    }
+
+    m_valueBox->setValue(value);
+    connect(m_valueBox, &ScientificSpinBox::valueChanged, this,
+            &ParameterTuningDelegate::editorValueChanged);
+
+    // initializing slider
+    m_slider = new QSlider(Qt::Horizontal);
+    m_slider->setFocusPolicy(Qt::StrongFocus);
+    m_slider->setTickPosition(QSlider::NoTicks);
+    m_slider->setTickInterval(1);
+    m_slider->setSingleStep(1);
+    m_slider->setRange(m_tuning_info.m_smin, m_tuning_info.m_smax);
+
+    updateSlider(value);
+
+    m_contentWidget = new QWidget(parent);
+    m_contentLayout = new QHBoxLayout(parent);
+    m_contentLayout->setMargin(0);
+    m_contentLayout->setSpacing(0);
+    m_contentLayout->addWidget(m_valueBox);
+    m_contentLayout->addWidget(m_slider);
+
+    // FIXME there is an issue with time of life of editor .vs. item
+    //        m_currentItem->mapper()->setOnValueChange(
+    //                      [this](){
+    //            if(m_valueBox && m_currentItem)
+    //              m_valueBox->setValue(m_currentItem->value().toDouble());
+    //        }, this);
+
+    //        m_currentItem->mapper()->setOnItemDestroy(
+    //                    [this](SessionItem *) {
+    //            m_currentItem = 0;
+    //        }, this);
+
+    m_contentWidget->setLayout(m_contentLayout);
+
+    return m_contentWidget;
 }
 
 void ParameterTuningDelegate::updateSlider(double value) const
diff --git a/GUI/Views/FitWidgets/ParameterTuningDelegate.h b/GUI/Views/FitWidgets/ParameterTuningDelegate.h
index 316727b867ba7ba486e138c040be7cc4931d668d..385776c1704c63dcc17b9e0cad3e33f727f18dd9 100644
--- a/GUI/Views/FitWidgets/ParameterTuningDelegate.h
+++ b/GUI/Views/FitWidgets/ParameterTuningDelegate.h
@@ -35,7 +35,7 @@ public:
         void setRangeFactor(double range_factor);
         void setItemLimits(const RealLimits& item_limits);
         int value_to_slider(double value);
-        double slider_to_value(int slider);
+        double slider_to_value(int slider) const;
         double step() const;
         int m_smin;
         int m_smax;
diff --git a/GUI/Views/InstrumentWidgets/InstrumentSelectorWidget.cpp b/GUI/Views/InstrumentWidgets/InstrumentSelectorWidget.cpp
index db228e3703b4110e16f96b3540198a49bb58b547..9d5f8fcd101cf26275cd2175d40dea3f94184db5 100644
--- a/GUI/Views/InstrumentWidgets/InstrumentSelectorWidget.cpp
+++ b/GUI/Views/InstrumentWidgets/InstrumentSelectorWidget.cpp
@@ -129,7 +129,7 @@ QList<QAction*> InstrumentSelectorWidget::toolbarActions() const
         m_storeInLibraryAction, m_loadFromLibraryAction};
 }
 
-void InstrumentSelectorWidget::onContextMenuRequest(const QPoint& point)
+void InstrumentSelectorWidget::onContextMenuRequest(const QPoint& point) const
 {
     QMenu menu;
     menu.addAction(m_copyAction);
diff --git a/GUI/Views/InstrumentWidgets/InstrumentSelectorWidget.h b/GUI/Views/InstrumentWidgets/InstrumentSelectorWidget.h
index 05328c887c2a968d2b65081bd842601f2980dfed..e42bc987bb95dadd8c83c78416c296afb82e9795 100644
--- a/GUI/Views/InstrumentWidgets/InstrumentSelectorWidget.h
+++ b/GUI/Views/InstrumentWidgets/InstrumentSelectorWidget.h
@@ -36,7 +36,7 @@ public:
     QList<QAction*> toolbarActions() const;
 
 private slots:
-    void onContextMenuRequest(const QPoint& point);
+    void onContextMenuRequest(const QPoint& point) const;
     void onNewGisas();
     void onNewOffSpecular();
     void onNewSpecular();