diff --git a/src/chunks.cpp b/src/chunks.cpp
index 30bb538..40847dd 100644
--- a/src/chunks.cpp
+++ b/src/chunks.cpp
@@ -62,7 +62,7 @@ bool Chunks::setIODevice(QIODevice &ioDevice)
 
 // ***************************************** Getting data out of Chunks
 
-QByteArray Chunks::data(qint64 pos, qint64 maxSize, QByteArray *highlighted)
+QByteArray Chunks::data(qint64 pos, qint64 maxSize, QByteArray *highlighted) const
 {
     qint64 ioDelta = 0;
     int chunkIdx = 0;
@@ -147,7 +147,7 @@ QByteArray Chunks::data(qint64 pos, qint64 maxSize, QByteArray *highlighted)
     return buffer;
 }
 
-bool Chunks::write(QIODevice &iODevice, qint64 pos, qint64 count)
+bool Chunks::write(QIODevice &iODevice, qint64 pos, qint64 count) const
 {
     if (count == -1)
         count = _size;
@@ -176,7 +176,7 @@ void Chunks::setDataChanged(qint64 pos, bool dataChanged)
     _chunks[chunkIdx].dataChanged[(int)posInBa] = char(dataChanged);
 }
 
-bool Chunks::dataChanged(qint64 pos)
+bool Chunks::dataChanged(qint64 pos) const
 {
     foreach (Chunk chunk, _chunks)
     {
@@ -191,7 +191,7 @@ bool Chunks::dataChanged(qint64 pos)
 
 // ***************************************** Search API
 
-qint64 Chunks::indexOf(const QByteArray &ba, qint64 from)
+qint64 Chunks::indexOf(const QByteArray &ba, qint64 from) const
 {
     qint64 result = -1;
     QByteArray buffer;
@@ -206,7 +206,7 @@ qint64 Chunks::indexOf(const QByteArray &ba, qint64 from)
     return result;
 }
 
-qint64 Chunks::lastIndexOf(const QByteArray &ba, qint64 from)
+qint64 Chunks::lastIndexOf(const QByteArray &ba, qint64 from) const
 {
     qint64 result = -1;
     QByteArray buffer;
@@ -276,22 +276,22 @@ bool Chunks::removeAt(qint64 pos)
 
 // ***************************************** Utility functions
 
-char Chunks::operator[](qint64 pos)
+char Chunks::operator[](qint64 pos) const
 {
     return data(pos, 1).at(0);
 }
 
-qint64 Chunks::pos()
+qint64 Chunks::pos() const
 {
     return _pos;
 }
 
-qint64 Chunks::size()
+qint64 Chunks::size() const
 {
     return _size;
 }
 
-int Chunks::getChunkIndex(qint64 absPos)
+int Chunks::getChunkIndex(qint64 absPos) const
 {
     // This routine checks, if there is already a copied chunk available. If os, it
     // returns a reference to it. If there is no copied chunk available, original
diff --git a/src/chunks.h b/src/chunks.h
index c516371..1291328 100644
--- a/src/chunks.h
+++ b/src/chunks.h
@@ -54,16 +54,16 @@ Q_OBJECT
     bool setIODevice(QIODevice &ioDevice);
 
     // Getting data out of Chunks
-    QByteArray data(qint64 pos=0, qint64 count=-1, QByteArray *highlighted=0);
-    bool write(QIODevice &iODevice, qint64 pos=0, qint64 count=-1);
+    QByteArray data(qint64 pos=0, qint64 count=-1, QByteArray *highlighted=0) const;
+    bool write(QIODevice &iODevice, qint64 pos=0, qint64 count=-1) const;
 
     // Set and get highlighting infos
     void setDataChanged(qint64 pos, bool dataChanged);
-    bool dataChanged(qint64 pos);
+    bool dataChanged(qint64 pos) const;
 
     // Search API
-    qint64 indexOf(const QByteArray &ba, qint64 from);
-    qint64 lastIndexOf(const QByteArray &ba, qint64 from);
+    qint64 indexOf(const QByteArray &ba, qint64 from) const;
+    qint64 lastIndexOf(const QByteArray &ba, qint64 from) const;
 
     // Char manipulations
     bool insert(qint64 pos, char b);
@@ -71,18 +71,18 @@ Q_OBJECT
     bool removeAt(qint64 pos);
 
     // Utility functions
-    char operator[](qint64 pos);
-    qint64 pos();
-    qint64 size();
+    char operator[](qint64 pos) const;
+    qint64 pos() const;
+    qint64 size() const;
 
 
 private:
-    int getChunkIndex(qint64 absPos);
+    int getChunkIndex(qint64 absPos) const;
 
     QIODevice * _ioDevice;
     qint64 _pos;
     qint64 _size;
-    QList<Chunk> _chunks;
+    mutable QList<Chunk> _chunks;
 
 #ifdef MODUL_TEST
 public:
diff --git a/src/color_manager.cpp b/src/color_manager.cpp
index 2d35bf8..a148409 100644
--- a/src/color_manager.cpp
+++ b/src/color_manager.cpp
@@ -47,12 +47,12 @@ ColoredArea::ColoredArea(qint64 posStart, qint64 posEnd, QPen pen, QBrush backgr
     _areaStyle = background;
 }
 
-QPen ColoredArea::fontPen()
+QPen ColoredArea::fontPen() const
 {
     return _fontColor;
 }
 
-QColor ColoredArea::fontColor()
+QColor ColoredArea::fontColor() const
 {
     return _fontColor.color();
 }
@@ -62,12 +62,12 @@ void ColoredArea::setFontColor(QColor color)
     _fontColor = QPen(color);
 }
 
-QColor ColoredArea::areaColor()
+QColor ColoredArea::areaColor() const
 {
     return _areaStyle.color();
 }
 
-QBrush ColoredArea::areaStyle()
+QBrush ColoredArea::areaStyle() const
 {
     return _areaStyle;
 }
@@ -82,21 +82,21 @@ void ColoredArea::setAreaStyle(QBrush backround)
     _areaStyle = backround;
 }
 
-qint64 ColoredArea::posStart()
+qint64 ColoredArea::posStart() const
 {
     return _posStart;
-};
+}
 
-qint64 ColoredArea::posEnd()
+qint64 ColoredArea::posEnd() const
 {
     return _posEnd;
-};
+}
 
 void ColoredArea::setRange(qint64 posStart, qint64 posEnd)
 {
     _posStart = posStart;
     _posEnd = posEnd;
-};
+}
 
 void ColoredArea::clear() 
 {
@@ -111,7 +111,7 @@ ColorManager::ColorManager()
 {
     QPalette palette = qApp->palette();
     setPalette(palette);
-};
+}
 
 void ColorManager::setPalette(const QPalette &palette)
 {
@@ -123,7 +123,7 @@ void ColorManager::setPalette(const QPalette &palette)
 }
 
 // read only, copy of relevant ColoredArea is returned: you can't change anything
-ColoredArea ColorManager::markedArea(qint64 pos, Area area, Chunks *chunks)
+ColoredArea ColorManager::markedArea(qint64 pos, Area area, Chunks *chunks) const
 {
     // prio 1 selection
     if (pos >= _selection.posStart() && pos < _selection.posEnd())
@@ -145,9 +145,9 @@ ColoredArea ColorManager::markedArea(qint64 pos, Area area, Chunks *chunks)
     }
     // nothing found -> standard colors
     return this->notMarked(area);
-};
+}
 
-ColoredArea& ColorManager::notMarked(Area area)
+const ColoredArea &ColorManager::notMarked(Area area) const
 {
     switch (area) {
         case Area::Address:
@@ -163,15 +163,25 @@ ColoredArea& ColorManager::notMarked(Area area)
     return _hex; // should never happen
 }
 
-ColoredArea& ColorManager::selection()
+const ColoredArea &ColorManager::selection() const
+{
+    return _selection;
+}
+
+ColoredArea &ColorManager::selection()
 {
     return _selection;
-};
+}
+
+const ColoredArea& ColorManager::highlighting() const
+{
+    return _highlighting;
+}
 
 ColoredArea& ColorManager::highlighting()
 {
     return _highlighting;
-};
+}
 
 void ColorManager::addUserArea(qint64 posStart, qint64 posEnd, QColor fontColor, QBrush areaStyle)
 {
@@ -182,4 +192,4 @@ void ColorManager::addUserArea(qint64 posStart, qint64 posEnd, QColor fontColor,
 void ColorManager::clearUserAreas()
 {
     _userAreas.clear();
-}
\ No newline at end of file
+}
diff --git a/src/color_manager.h b/src/color_manager.h
index b7140f1..01961c6 100644
--- a/src/color_manager.h
+++ b/src/color_manager.h
@@ -47,25 +47,25 @@ enum Area {
 class ColoredArea
 {
 public:
-    // Cunstructors
+    // Constructors
     ColoredArea();
     ColoredArea(QPen pen, QBrush background);
     ColoredArea(qint64 posStart, qint64 posEnd, QPen pen, QBrush background);
 
     // Property to set/get font color
-    QColor fontColor();
+    QColor fontColor() const;
     void setFontColor(QColor color);
 
     // Property to set/get area style
-    QColor areaColor();
-    QBrush areaStyle();
+    QColor areaColor() const;
+    QBrush areaStyle() const;
     void setAreaColor(QColor color);
     void setAreaStyle(QBrush background);
 
     // other Methods to acces and set internal data
-    QPen fontPen();
-    qint64 posStart();
-    qint64 posEnd();
+    QPen fontPen() const;
+    qint64 posStart() const;
+    qint64 posEnd() const;
     void setRange(qint64 posStart, qint64 posEnd);
     void clear();
 
@@ -87,15 +87,17 @@ class ColorManager
     void setPalette(const QPalette &palette);
 
     // Method returns color definitions for data at position pos in area area
-    ColoredArea markedArea(qint64 pos, Area area, Chunks *chunks);
+    ColoredArea markedArea(qint64 pos, Area area, Chunks *chunks) const;
 
     // Method returns standard collors (without marking)
-    ColoredArea& notMarked(Area);
+    const ColoredArea& notMarked(Area) const;
 
     // Get the selection color definitions
+    const ColoredArea& selection() const;
     ColoredArea& selection();
 
     // Get the highlighting color definitions
+    const ColoredArea& highlighting() const;
     ColoredArea& highlighting();
 
     // Add a user defined area
@@ -116,4 +118,4 @@ class ColorManager
 
 /** \endcond docNever */
 
-#endif // COLOR_MANAGER_H
\ No newline at end of file
+#endif // COLOR_MANAGER_H
diff --git a/src/commands.cpp b/src/commands.cpp
index 55f90ad..0f7eedb 100644
--- a/src/commands.cpp
+++ b/src/commands.cpp
@@ -113,7 +113,6 @@ UndoStack::UndoStack(Chunks * chunks, QObject * parent)
     : QUndoStack(parent)
 {
     _chunks = chunks;
-    _parent = parent;
     this->setUndoLimit(1000);
 }
 
diff --git a/src/commands.h b/src/commands.h
index e6732dc..45b4359 100644
--- a/src/commands.h
+++ b/src/commands.h
@@ -57,7 +57,6 @@ class UndoStack : public QUndoStack
 
 private:
     Chunks * _chunks;
-    QObject * _parent;
 };
 
 /** \endcond docNever */
diff --git a/src/qhexedit.cpp b/src/qhexedit.cpp
index c563875..9736579 100644
--- a/src/qhexedit.cpp
+++ b/src/qhexedit.cpp
@@ -88,7 +88,7 @@ void QHexEdit::setAddressArea(bool addressArea)
     viewport()->update();
 }
 
-bool QHexEdit::addressArea()
+bool QHexEdit::addressArea() const
 {
     return _addressArea;
 }
@@ -101,7 +101,7 @@ void QHexEdit::setAddressOffset(qint64 addressOffset)
     viewport()->update();
 }
 
-qint64 QHexEdit::addressOffset()
+qint64 QHexEdit::addressOffset() const
 {
     return _addressOffset;
 }
@@ -114,7 +114,7 @@ void QHexEdit::setAddressWidth(int addressWidth)
     viewport()->update();
 }
 
-int QHexEdit::addressWidth()
+int QHexEdit::addressWidth() const
 {
     qint64 size = _chunks->size();
     int n = 1;
@@ -139,7 +139,7 @@ void QHexEdit::setAsciiArea(bool asciiArea)
     viewport()->update();
 }
 
-bool QHexEdit::asciiArea()
+bool QHexEdit::asciiArea() const
 {
     return _asciiArea;
 }
@@ -154,12 +154,12 @@ void QHexEdit::setBytesPerLine(int count)
     viewport()->update();
 }
 
-int QHexEdit::bytesPerLine()
+int QHexEdit::bytesPerLine() const
 {
     return _bytesPerLine;
 }
 
-char QHexEdit::defaultChar()
+char QHexEdit::defaultChar() const
 {
     return _defaultChar;
 }
@@ -254,7 +254,7 @@ qint64 QHexEdit::cursorPosition(QPoint pos)
     return result;
 }
 
-qint64 QHexEdit::cursorPosition()
+qint64 QHexEdit::cursorPosition() const
 {
     return _cursorPosition;
 }
@@ -277,7 +277,7 @@ void QHexEdit::setHighlighting(bool highlighting)
     viewport()->update();
 }
 
-bool QHexEdit::highlighting()
+bool QHexEdit::highlighting() const
 {
     return _highlighting;
 }
@@ -288,7 +288,7 @@ void QHexEdit::setHighlightingColor(const QColor &color)
     viewport()->update();
 }
 
-QColor QHexEdit::highlightingColor()
+QColor QHexEdit::highlightingColor() const
 {
     return _colorManager->highlighting().areaColor();
 }
@@ -299,12 +299,12 @@ void QHexEdit::setOverwriteMode(bool overwriteMode)
     emit overwriteModeChanged(overwriteMode);
 }
 
-bool QHexEdit::overwriteMode()
+bool QHexEdit::overwriteMode() const
 {
     return _overwriteMode;
 }
 
-bool QHexEdit::isReadOnly()
+bool QHexEdit::isReadOnly() const
 {
     return _readOnly;
 }
@@ -320,7 +320,7 @@ void QHexEdit::setHexCaps(const bool isCaps)
     viewport()->update();
 }
 
-bool QHexEdit::hexCaps()
+bool QHexEdit::hexCaps() const
 {
     return _hexCaps;
 }
@@ -331,7 +331,7 @@ void QHexEdit::setDynamicBytesPerLine(const bool isDynamic)
     resizeEvent(nullptr);
 }
 
-bool QHexEdit::dynamicBytesPerLine()
+bool QHexEdit::dynamicBytesPerLine() const
 {
     return _dynamicBytesPerLine;
 }
@@ -344,12 +344,12 @@ bool QHexEdit::setData(QIODevice &iODevice)
     return ok;
 }
 
-QByteArray QHexEdit::dataAt(qint64 pos, qint64 count)
+QByteArray QHexEdit::dataAt(qint64 pos, qint64 count) const
 {
     return _chunks->data(pos, count);
 }
 
-bool QHexEdit::write(QIODevice &iODevice, qint64 pos, qint64 count)
+bool QHexEdit::write(QIODevice &iODevice, qint64 pos, qint64 count) const
 {
     return _chunks->write(iODevice, pos, count);
 }
@@ -427,7 +427,7 @@ qint64 QHexEdit::indexOf(const QByteArray &ba, qint64 from)
     return pos;
 }
 
-bool QHexEdit::isModified()
+bool QHexEdit::isModified() const
 {
     return _modified;
 }
@@ -453,7 +453,7 @@ void QHexEdit::redo()
     refresh();
 }
 
-QString QHexEdit::selectionToReadableString()
+QString QHexEdit::selectionToReadableString() const
 {
     QByteArray ba = _chunks->data(getSelectionBegin(), getSelectionEnd() - getSelectionBegin());
     return toReadable(ba);
@@ -1094,12 +1094,12 @@ void QHexEdit::setSelection(qint64 pos)
     _colorManager->selection().setRange(_bSelectionBegin, _bSelectionEnd);
 }
 
-qint64 QHexEdit::getSelectionBegin()
+qint64 QHexEdit::getSelectionBegin() const
 {
     return _bSelectionBegin;
 }
 
-qint64 QHexEdit::getSelectionEnd()
+qint64 QHexEdit::getSelectionEnd() const
 {
     return _bSelectionEnd;
 }
@@ -1179,7 +1179,7 @@ void QHexEdit::readBuffers()
     _hexDataShown = QByteArray(_dataShown.toHex());
 }
 
-QString QHexEdit::toReadable(const QByteArray &ba)
+QString QHexEdit::toReadable(const QByteArray &ba) const
 {
     QString result;
 
diff --git a/src/qhexedit.h b/src/qhexedit.h
index fadaba2..94d4cd7 100644
--- a/src/qhexedit.h
+++ b/src/qhexedit.h
@@ -174,12 +174,12 @@ class QHEXEDIT_API QHexEdit : public QAbstractScrollArea
     /*! Gives back the data as a QByteArray starting at position \param pos and
     delivering \param count bytes.
     */
-    QByteArray dataAt(qint64 pos, qint64 count=-1);
+    QByteArray dataAt(qint64 pos, qint64 count=-1) const;
 
     /*! Gives back the data into a \param iODevice starting at position \param pos
     and delivering \param count bytes.
     */
-    bool write(QIODevice &iODevice, qint64 pos=0, qint64 count=-1);
+    bool write(QIODevice &iODevice, qint64 pos=0, qint64 count=-1) const;
 
 
     // Char handling
@@ -262,18 +262,18 @@ class QHEXEDIT_API QHexEdit : public QAbstractScrollArea
     /*! Returns if any changes where done on document
      * \return true when document is modified else false
      */
-    bool isModified();
+    bool isModified() const;
 
     /*! Find last occurrence of ba in QHexEdit data
      * \param ba Data to find
      * \param from Point where the search starts
-     * \return pos if fond, else -1
+     * \return pos if found, else -1
      */
     qint64 lastIndexOf(const QByteArray &ba, qint64 from);
 
     /*! Gives back a formatted image of the selected content of QHexEdit
     */
-    QString selectionToReadableString();
+    QString selectionToReadableString() const;
 
     /*! Return the selected content of QHexEdit as QByteArray
     */
@@ -319,46 +319,46 @@ public slots:
     ~QHexEdit();
 
     // Properties
-    bool addressArea();
+    bool addressArea() const;
     void setAddressArea(bool addressArea);
 
-    qint64 addressOffset();
+    qint64 addressOffset() const;
     void setAddressOffset(qint64 addressArea);
 
-    int addressWidth();
+    int addressWidth() const;
     void setAddressWidth(int addressWidth);
 
-    bool asciiArea();
+    bool asciiArea() const;
     void setAsciiArea(bool asciiArea);
 
-    int bytesPerLine();
+    int bytesPerLine() const;
     void setBytesPerLine(int count);
 
-    char defaultChar();
+    char defaultChar() const;
     void setDefaultChar(char defaultChar);
 
-    qint64 cursorPosition();
+    qint64 cursorPosition() const;
     void setCursorPosition(qint64 position);
 
     QByteArray data();
     void setData(const QByteArray &ba);
 
     void setHexCaps(const bool isCaps);
-    bool hexCaps();
+    bool hexCaps() const;
 
     void setDynamicBytesPerLine(const bool isDynamic);
-    bool dynamicBytesPerLine();
+    bool dynamicBytesPerLine() const;
 
-    bool highlighting();
+    bool highlighting() const;
     void setHighlighting(bool mode);
 
-    QColor highlightingColor();
+    QColor highlightingColor() const;
     void setHighlightingColor(const QColor &color);
 
-    bool overwriteMode();
+    bool overwriteMode() const;
     void setOverwriteMode(bool overwriteMode);
 
-    bool isReadOnly();
+    bool isReadOnly() const;
     void setReadOnly(bool readOnly);
 
 protected:
@@ -375,13 +375,13 @@ public slots:
     void resetSelection(qint64 pos);            // set selectionStart and selectionEnd to pos
     void resetSelection();                      // set selectionEnd to selectionStart
     void setSelection(qint64 pos);              // set min (if below init) or max (if greater init)
-    qint64 getSelectionBegin();
-    qint64 getSelectionEnd();
+    qint64 getSelectionBegin() const;
+    qint64 getSelectionEnd() const;
 
     // Private utility functions
     void init();
     void readBuffers();
-    QString toReadable(const QByteArray &ba);
+    QString toReadable(const QByteArray &ba) const;
 
 private slots:
     void adjust();                              // recalc pixel positions