diff --git a/publicWidgets/objectSelectionWidget/TreeItemObjectSelection.cc b/publicWidgets/objectSelectionWidget/TreeItemObjectSelection.cc
index 54dbb2880d6722e607ded46bfec99458b78e8198..ea4538184139df9bbc70eec9f26ad2f67467d9a1 100644
--- a/publicWidgets/objectSelectionWidget/TreeItemObjectSelection.cc
+++ b/publicWidgets/objectSelectionWidget/TreeItemObjectSelection.cc
@@ -47,7 +47,7 @@
 
 //--------------------------------------------------------------------------------
 
-TreeItemObjectSelection::TreeItemObjectSelection(int _id, QString _name, DataType _type, TreeItemObjectSelection* _parent) :
+TreeItemObjectSelection::TreeItemObjectSelection(int _id, const QString& _name, DataType _type, TreeItemObjectSelection* _parent) :
   id_(_id),
   dataType_(_type),
   visible_(true),
@@ -128,7 +128,7 @@ QString TreeItemObjectSelection::name() {
 
 //--------------------------------------------------------------------------------
 
-void TreeItemObjectSelection::name(QString _name ) {
+void TreeItemObjectSelection::name(const QString& _name ) {
   name_ = _name;
 }
 
diff --git a/publicWidgets/objectSelectionWidget/TreeItemObjectSelection.hh b/publicWidgets/objectSelectionWidget/TreeItemObjectSelection.hh
index 253416e2e6bb944cc2866cc785eb066c60a60cd0..6b3ac741e3ae10c866a4a403e9a42bf6d198ac85 100644
--- a/publicWidgets/objectSelectionWidget/TreeItemObjectSelection.hh
+++ b/publicWidgets/objectSelectionWidget/TreeItemObjectSelection.hh
@@ -54,7 +54,7 @@ class TreeItemObjectSelection {
 
   public :
 
-    TreeItemObjectSelection(int _id, QString _name, DataType _type, TreeItemObjectSelection* _parent);
+    TreeItemObjectSelection(int _id, const QString &_name, DataType _type, TreeItemObjectSelection* _parent);
 
   // static members
   public:
@@ -82,7 +82,7 @@ class TreeItemObjectSelection {
 
     /// name
     QString name( );
-    void name( QString _name );
+    void name(const QString &_name );
 
   private:
     bool visible_;
diff --git a/widgets/addEmptyWidget/addEmptyWidget.cc b/widgets/addEmptyWidget/addEmptyWidget.cc
index 559dc298cd362e801898e7c0bf835ba61cec7ba8..63415d2b9de04346c3e1f419fc8f47f815fdd987 100644
--- a/widgets/addEmptyWidget/addEmptyWidget.cc
+++ b/widgets/addEmptyWidget/addEmptyWidget.cc
@@ -47,7 +47,7 @@
 #include "addEmptyWidget.hh"
 #include <OpenFlipper/common/GlobalOptions.hh>
 
-addEmptyWidget::addEmptyWidget(std::vector< DataType > _types , QStringList _typeNames, QWidget *parent)
+addEmptyWidget::addEmptyWidget(const std::vector< DataType >& _types , const QStringList& _typeNames, QWidget *parent)
   : QDialog(parent),
     types_(_types),
     typeNames_(_typeNames)
diff --git a/widgets/addEmptyWidget/addEmptyWidget.hh b/widgets/addEmptyWidget/addEmptyWidget.hh
index 0db2cc75de5aef095bf6d2c83bd8f37067e41672..a6659cf7f6059e61d142e4c62dbf0e6f3c12760f 100644
--- a/widgets/addEmptyWidget/addEmptyWidget.hh
+++ b/widgets/addEmptyWidget/addEmptyWidget.hh
@@ -49,7 +49,7 @@ class addEmptyWidget : public QDialog, public Ui::addEmpty
 {
   Q_OBJECT
   public:
-    addEmptyWidget(std::vector< DataType > _types , QStringList _typeNames, QWidget *parent = 0 );
+    addEmptyWidget(const std::vector<DataType> &_types , const QStringList &_typeNames, QWidget *parent = 0 );
     
   private:
     std::vector< DataType > types_;
diff --git a/widgets/coreWidget/CoreWidget.hh b/widgets/coreWidget/CoreWidget.hh
index b82e9d2b2f2bbd229d244c15647ad3f1e6543298..bde584ace43609476d5263714723483883afd775 100644
--- a/widgets/coreWidget/CoreWidget.hh
+++ b/widgets/coreWidget/CoreWidget.hh
@@ -145,7 +145,7 @@ struct ViewMode{
 
 class StackWidgetInfo {
   public:
-    StackWidgetInfo(bool _editable,QString _name,QWidget* _widget);
+    StackWidgetInfo(bool _editable, const QString &_name, QWidget* _widget);
 
     bool editable;
     QString name;
@@ -1036,7 +1036,7 @@ public:
     void applicationSnapshot();
 
     /// Set the snapshot name
-    void applicationSnapshotName(QString _name);
+    void applicationSnapshotName(const QString &_name);
 
     /// Scriptable snapshot method offering full control
     void viewerSnapshot(QString file_name, bool store_comments,
@@ -1054,7 +1054,7 @@ public:
 
   public:
 
-    void writeImageAsynchronously(QImage* _image, const QString _name);
+    void writeImageAsynchronously(QImage* _image, const QString &_name);
 
   private:
 
@@ -1076,7 +1076,7 @@ public:
   //===========================================================================
 
   private slots:
-    void slotGetStackWidget( QString _name, QWidget*& _widget );
+    void slotGetStackWidget(const QString &_name, QWidget*& _widget );
     void slotAddStackWidget( QString _name, QWidget* _widget );
     void slotUpdateStackWidget( QString _name, QWidget* _widget );
 
diff --git a/widgets/coreWidget/SideArea.cc b/widgets/coreWidget/SideArea.cc
index 4c3dfbc082d9b71c24c9244fe5f16c8c4da851c5..0755345e47121cef97c126b6d2bbffd1b02cb9a9 100644
--- a/widgets/coreWidget/SideArea.cc
+++ b/widgets/coreWidget/SideArea.cc
@@ -209,7 +209,7 @@ void SideArea::restoreViewModeState(const QString& _viewMode) {
 
 //-----------------------------------------------------------------------------
 
-void SideArea::setElementActive(QString _name, bool _active)
+void SideArea::setElementActive(const QString& _name, bool _active)
 {
   for (int i=0; i < items_.count(); i++)
     if ( items_[i]->name() == _name ){
diff --git a/widgets/coreWidget/SideArea.hh b/widgets/coreWidget/SideArea.hh
index 8d187fb94a03b0e64c498e46c5462f1091484db2..26f3170cdc8fb6ba4f0bc523d632b17326daf0c9 100644
--- a/widgets/coreWidget/SideArea.hh
+++ b/widgets/coreWidget/SideArea.hh
@@ -110,7 +110,7 @@ class SideArea : public QWidget {
     void restoreViewModeState(const QString& _viewMode);
 
     /// set the active state of given element
-    void setElementActive(QString _name, bool _active);
+    void setElementActive(const QString &_name, bool _active);
 
     /// Move a toolbox widget to a given position
     void moveItemToPosition(const QString& _name, int _position);
diff --git a/widgets/coreWidget/StackWidget.cc b/widgets/coreWidget/StackWidget.cc
index 1d2130af309f9e3167f9d58a4948ae5c2aaa8990..17085166d2ac5344d1c9038ecb51d20bb66b13ce 100644
--- a/widgets/coreWidget/StackWidget.cc
+++ b/widgets/coreWidget/StackWidget.cc
@@ -57,14 +57,14 @@
 
 //== IMPLEMENTATION ==========================================================
 
-StackWidgetInfo::StackWidgetInfo(bool _editable,QString _name,QWidget* _widget) :
+StackWidgetInfo::StackWidgetInfo(bool _editable,const QString& _name,QWidget* _widget) :
     editable(_editable),
     name(_name),
     widget(_widget)
 {
 }
 
-void CoreWidget::slotGetStackWidget( QString _name, QWidget*& _widget) {
+void CoreWidget::slotGetStackWidget(const QString& _name, QWidget*& _widget) {
   
   for ( uint i = 0 ; i < stackWidgetList_.size(); ++i) {
     if ( stackWidgetList_[i].name == _name ) {
diff --git a/widgets/coreWidget/picking.cc b/widgets/coreWidget/picking.cc
index 4f0c65aa8890abbdd79db252395fc8330eb12a9d..723acf855b11c98b3e2003a618a0934df79d1275 100644
--- a/widgets/coreWidget/picking.cc
+++ b/widgets/coreWidget/picking.cc
@@ -434,8 +434,8 @@ void CoreWidget::setPickModeMouseTracking(const std::string& _name, bool _mouseT
 
       //switch cursor if pickMode is active
       if (pick_mode_name_ == _name && pickingMode() )
-        for ( unsigned int i = 0 ; i < OpenFlipper::Options::examinerWidgets() ; ++i )
-          examiner_widgets_[i]->trackMouse(_mouseTracking);
+        for ( unsigned int j = 0 ; j < OpenFlipper::Options::examinerWidgets() ; ++j )
+          examiner_widgets_[j]->trackMouse(_mouseTracking);
       break;
     }
 }
diff --git a/widgets/coreWidget/viewerControl.cc b/widgets/coreWidget/viewerControl.cc
index b5258732f721d16357df46291fe6ad5426dd67b7..a8978ddf9e5b28e0823c3cba4c8338c3b4b5e810 100644
--- a/widgets/coreWidget/viewerControl.cc
+++ b/widgets/coreWidget/viewerControl.cc
@@ -896,18 +896,18 @@ void CoreWidget::viewerSnapshot() {
   }
 }
 
-void CoreWidget::applicationSnapshotName(QString _name) {
+void CoreWidget::applicationSnapshotName(const QString& _name) {
   snapshotName_ = _name;
 }
 
 
-void writeImageQImage(QImage* _image, const QString _name) {
+void writeImageQImage(QImage* _image, const QString& _name) {
 
     _image->save(_name);
     delete _image;
 }
 
-void CoreWidget::writeImageAsynchronously(QImage* _image, const QString _name) {
+void CoreWidget::writeImageAsynchronously(QImage* _image, const QString& _name) {
 
     QFuture<void>* future = new QFuture<void>();
     *future = QtConcurrent::run(writeImageQImage, _image, _name);
diff --git a/widgets/filePicker/FilePicker.cc b/widgets/filePicker/FilePicker.cc
index 2b601bc598fc7937f542ed739d196585825374e6..0d8c2e1116fa9b40137b7c5ea409158b7237fdd7 100644
--- a/widgets/filePicker/FilePicker.cc
+++ b/widgets/filePicker/FilePicker.cc
@@ -55,7 +55,7 @@ FilePicker::FilePicker(QWidget *parent) :
     init();
 }
 
-FilePicker::FilePicker(QString recent_files_ini_key,
+FilePicker::FilePicker(const QString& recent_files_ini_key,
                            DialogType dialog_type,
                            QWidget *parent)  :
     QWidget(parent),
@@ -94,7 +94,7 @@ void FilePicker::init() {
             this, SLOT( path_changed() ));
 }
 
-void FilePicker::set_recent_files_ini_key(QString value) {
+void FilePicker::set_recent_files_ini_key(const QString& value) {
     recent_files_ini_key_ = value;
     textBox_->clear();
     textBox_->insertItems(
diff --git a/widgets/filePicker/FilePicker.hh b/widgets/filePicker/FilePicker.hh
index 0f6a164e9ff86ec37640308d563905cc4e244954..503df8911a3d242e2a461b9a8af119647e0349b6 100644
--- a/widgets/filePicker/FilePicker.hh
+++ b/widgets/filePicker/FilePicker.hh
@@ -78,7 +78,7 @@ class DLLEXPORT FilePicker : public QWidget {
         };
 
         explicit FilePicker(QWidget *parent = 0);
-        explicit FilePicker(QString recent_files_ini_key,
+        explicit FilePicker(const QString &recent_files_ini_key,
                               DialogType dialog_type,
                               QWidget *parent = 0);
         virtual ~FilePicker();
@@ -97,7 +97,7 @@ class DLLEXPORT FilePicker : public QWidget {
         }
 
         QString recent_files_ini_key() { return recent_files_ini_key_; }
-        void set_recent_files_ini_key(QString value);
+        void set_recent_files_ini_key(const QString &value);
 
         QString dialog_title() { return dialog_title_; }
         void set_dialog_title(QString value) {
diff --git a/widgets/glWidget/QtSlideWindow.cc b/widgets/glWidget/QtSlideWindow.cc
index 90fb5e98af0ea652aeaccc35c03505eb437271a7..7cd3f6825e32a4825aaf16cd98cd40874f09a0c5 100644
--- a/widgets/glWidget/QtSlideWindow.cc
+++ b/widgets/glWidget/QtSlideWindow.cc
@@ -72,7 +72,7 @@
 
 //== IMPLEMENTATION ==========================================================
 
-QtSlideWindow::QtSlideWindow(QString _name, QGraphicsItem *_parent) :
+QtSlideWindow::QtSlideWindow(const QString& _name, QGraphicsItem *_parent) :
     QGraphicsProxyWidget(_parent),
     name_(_name),
     mainWidget_(0),
diff --git a/widgets/glWidget/QtSlideWindow.hh b/widgets/glWidget/QtSlideWindow.hh
index 7f8059e1b61abc02d0e51bb221f8ed45999932b8..e9648423fbacad49aba3b4f6819fa8ee42f0b361 100644
--- a/widgets/glWidget/QtSlideWindow.hh
+++ b/widgets/glWidget/QtSlideWindow.hh
@@ -83,7 +83,7 @@ class DLLEXPORT QtSlideWindow : public QGraphicsProxyWidget
     \param _name displayed titlebar name
     \param _parent parent graphics item
     */
-    QtSlideWindow (QString _name = 0, QGraphicsItem *_parent = 0);
+    QtSlideWindow (const QString &_name = 0, QGraphicsItem *_parent = 0);
 
     /// recalculate geometry
     void updateGeometry ();
diff --git a/widgets/loadWidget/FileOptionsDialog.cc b/widgets/loadWidget/FileOptionsDialog.cc
index d5214da9f2ba570e7b9cdfc83a5bfe3319ab29c2..c48eff2c9dc883beb373d28087cee69859e8f31a 100644
--- a/widgets/loadWidget/FileOptionsDialog.cc
+++ b/widgets/loadWidget/FileOptionsDialog.cc
@@ -43,7 +43,7 @@
 
 #include "FileOptionsDialog.hh"
 
-FileOptionsDialog::FileOptionsDialog(std::vector<fileTypes>& _supportedTypes, QStringList _extensions, bool _loadMode, QWidget *parent)
+FileOptionsDialog::FileOptionsDialog(std::vector<fileTypes>& _supportedTypes, const QStringList& _extensions, bool _loadMode, QWidget *parent)
   : QDialog(parent),
     ext_(_extensions),
     supportedTypes_(_supportedTypes),
@@ -207,7 +207,7 @@ bool FileOptionsDialog::makePluginDefault() {
   return defaultPluginBox_->isChecked();
 }
 
-void FileOptionsDialog::slotPluginChanged(QString _name){
+void FileOptionsDialog::slotPluginChanged(const QString& _name){
   
   QComboBox* box = dynamic_cast<QComboBox*>(QObject::sender());
 
diff --git a/widgets/loadWidget/FileOptionsDialog.hh b/widgets/loadWidget/FileOptionsDialog.hh
index a28a6fea36ba9a10c326e5b45aa73554a8ec4b31..e242125e04dd190461fc3b734ce25a5e591f11db 100644
--- a/widgets/loadWidget/FileOptionsDialog.hh
+++ b/widgets/loadWidget/FileOptionsDialog.hh
@@ -52,7 +52,7 @@ class FileOptionsDialog : public QDialog
 {
   Q_OBJECT
   public:
-    FileOptionsDialog(std::vector<fileTypes>& _supportedTypes, QStringList _extensions, bool _loadMode, QWidget *parent = 0 );
+    FileOptionsDialog(std::vector<fileTypes>& _supportedTypes, const QStringList &_extensions, bool _loadMode, QWidget *parent = 0 );
     ~FileOptionsDialog();
     
   private:
@@ -62,7 +62,7 @@ class FileOptionsDialog : public QDialog
     QTabWidget tabs_;
 
   private slots:
-    void slotPluginChanged(QString _name);
+    void slotPluginChanged(const QString &_name);
 
     void slotPluginDefault(int _state);
 
diff --git a/widgets/optionsWidget/keyBindings.cc b/widgets/optionsWidget/keyBindings.cc
index da8fa5fd905ce710cc7eb855e2d5e929724c0803..4ae2f2f70f2423a9d0f0627f267572823eadb208 100644
--- a/widgets/optionsWidget/keyBindings.cc
+++ b/widgets/optionsWidget/keyBindings.cc
@@ -47,7 +47,7 @@
 #include <QMessageBox>
 
 /// get the pluginInfo object corresponding to the given pluginName
-int OptionsWidget::getPluginInfo(QString pluginName){
+int OptionsWidget::getPluginInfo(const QString& pluginName){
   for (uint i=0; i < plugins_.size(); i++)
     if (plugins_[i].name == pluginName)
       return i;
diff --git a/widgets/optionsWidget/optionsWidget.hh b/widgets/optionsWidget/optionsWidget.hh
index 7ac682ecd87aa8dba0c067999cc1f6abfcf9f765..d494c8e270fb4bc3bf2b6b099ae7a539441a7a79 100644
--- a/widgets/optionsWidget/optionsWidget.hh
+++ b/widgets/optionsWidget/optionsWidget.hh
@@ -146,7 +146,7 @@ private:
 
    InverseKeyMap& keys_;
 
-   int getPluginInfo(QString pluginName);
+   int getPluginInfo(const QString &pluginName);
 
    void initKeyTree();
 
diff --git a/widgets/viewModeWidget/viewModeChangeWidget.cc b/widgets/viewModeWidget/viewModeChangeWidget.cc
index 51e58ff69e1e5949fd06829374d6fa7fa49d4786..2c4e4490484ceae2f97ea8b405f242f7b184a06e 100644
--- a/widgets/viewModeWidget/viewModeChangeWidget.cc
+++ b/widgets/viewModeWidget/viewModeChangeWidget.cc
@@ -93,7 +93,7 @@ void viewModeChangeWidget::showEvent(QShowEvent *event) {
 }
 
 /// overloaded show function
-void viewModeChangeWidget::update(QString _lastMode){
+void viewModeChangeWidget::update(const QString& _lastMode){
 
     //fill viewModeList
   viewModeList->clear();
diff --git a/widgets/viewModeWidget/viewModeChangeWidget.hh b/widgets/viewModeWidget/viewModeChangeWidget.hh
index 85e212172219aedd037a59827ee154155ae8799b..5e505a181cd89561ac41d47bd79c2ba2256888e5 100644
--- a/widgets/viewModeWidget/viewModeChangeWidget.hh
+++ b/widgets/viewModeWidget/viewModeChangeWidget.hh
@@ -56,7 +56,7 @@ class viewModeChangeWidget : public QWidget, public Ui::ViewModeChangeDialog
   public:
     viewModeChangeWidget(const QVector< ViewMode* >& _modes, QWidget *parent = 0 );
     
-    void update(QString _lastMode);
+    void update(const QString &_lastMode);
 
   public slots:
     void slot_update();