diff --git a/RedPandaIDE/compiler/compilerinfo.h b/RedPandaIDE/compiler/compilerinfo.h
index 1f0c3d53..56a7a289 100644
--- a/RedPandaIDE/compiler/compilerinfo.h
+++ b/RedPandaIDE/compiler/compilerinfo.h
@@ -4,7 +4,6 @@
 #include <QString>
 #include <QMap>
 #include <memory>
-#include <QMutex>
 #define COMPILER_CLANG "Clang"
 #define COMPILER_GCC "GCC"
 #define COMPILER_GCC_UTF8 "GCC_UTF8"
diff --git a/RedPandaIDE/parser/cppparser.cpp b/RedPandaIDE/parser/cppparser.cpp
index aed6dee4..39251297 100644
--- a/RedPandaIDE/parser/cppparser.cpp
+++ b/RedPandaIDE/parser/cppparser.cpp
@@ -142,7 +142,7 @@ void CppParser::clearProjectFiles()
     mProjectFiles.clear();
 }
 
-QList<PStatement> CppParser::getListOfFunctions(const QString &fileName, const QString &phrase, int line)
+QList<PStatement> CppParser::getListOfFunctions(const QString &fileName, const QString &phrase, int line) const
 {
     QMutexLocker locker(&mMutex);
     QList<PStatement> result;
@@ -185,7 +185,7 @@ QList<PStatement> CppParser::getListOfFunctions(const QString &fileName, const Q
     return result;
 }
 
-PStatement CppParser::findScopeStatement(const QString &filename, int line)
+PStatement CppParser::findScopeStatement(const QString &filename, int line) const
 {
     QMutexLocker locker(&mMutex);
     if (mParsing) {
@@ -203,13 +203,13 @@ PStatement CppParser::doFindScopeStatement(const QString &filename, int line) co
     return fileInfo->findScopeAtLine(line);
 }
 
-PParsedFileInfo CppParser::findFileInfo(const QString &filename)
+PParsedFileInfo CppParser::findFileInfo(const QString &filename) const
 {
     QMutexLocker locker(&mMutex);
     PParsedFileInfo fileInfo = mPreprocessor.findFileInfo(filename);
     return fileInfo;
 }
-QString CppParser::findFirstTemplateParamOf(const QString &fileName, const QString &phrase, const PStatement& currentScope)
+QString CppParser::findFirstTemplateParamOf(const QString &fileName, const QString &phrase, const PStatement& currentScope) const
 {
     QMutexLocker locker(&mMutex);
     if (mParsing)
@@ -217,7 +217,7 @@ QString CppParser::findFirstTemplateParamOf(const QString &fileName, const QStri
     return doFindFirstTemplateParamOf(fileName,phrase,currentScope);
 }
 
-QString CppParser::findTemplateParamOf(const QString &fileName, const QString &phrase, int index, const PStatement &currentScope)
+QString CppParser::findTemplateParamOf(const QString &fileName, const QString &phrase, int index, const PStatement &currentScope) const
 {
     QMutexLocker locker(&mMutex);
     if (mParsing)
@@ -225,7 +225,7 @@ QString CppParser::findTemplateParamOf(const QString &fileName, const QString &p
     return doFindTemplateParamOf(fileName,phrase,index,currentScope);
 }
 
-PStatement CppParser::findFunctionAt(const QString &fileName, int line)
+PStatement CppParser::findFunctionAt(const QString &fileName, int line) const
 {
     QMutexLocker locker(&mMutex);
     PParsedFileInfo fileInfo = mPreprocessor.findFileInfo(fileName);
@@ -262,7 +262,7 @@ int CppParser::findLastOperator(const QString &phrase) const
     return -1;
 }
 
-PStatementList CppParser::findNamespace(const QString &name)
+PStatementList CppParser::findNamespace(const QString &name) const
 {
     QMutexLocker locker(&mMutex);
     return doFindNamespace(name);
@@ -274,7 +274,7 @@ PStatementList CppParser::doFindNamespace(const QString &name) const
 }
 
 
-PStatement CppParser::findStatement(const QString &fullname)
+PStatement CppParser::findStatement(const QString &fullname) const
 {
     QMutexLocker locker(&mMutex);
     return doFindStatement(fullname);
@@ -309,7 +309,7 @@ PStatement CppParser::doFindStatement(const QString &fullname) const
     return statement;
 }
 
-PStatement CppParser::findStatementOf(const QString &fileName, const QString &phrase, int line)
+PStatement CppParser::findStatementOf(const QString &fileName, const QString &phrase, int line) const
 {
     QMutexLocker locker(&mMutex);
     if (mParsing)
@@ -324,7 +324,7 @@ PStatement CppParser::doFindStatementOf(const QString &fileName, const QString &
 PStatement CppParser::findStatementOf(const QString &fileName,
                                       const QString &phrase,
                                       const PStatement& currentScope,
-                                      PStatement &parentScopeType)
+                                      PStatement &parentScopeType) const
 {
     QMutexLocker locker(&mMutex);
     if (mParsing)
@@ -495,7 +495,7 @@ PStatement CppParser::doFindStatementOf(const QString &fileName,
 PEvalStatement CppParser::evalExpression(
         const QString &fileName,
         QStringList &phraseExpression,
-        const PStatement &currentScope)
+        const PStatement &currentScope) const
 {
     QMutexLocker locker(&mMutex);
     if (mParsing)
@@ -518,7 +518,7 @@ PStatement CppParser::doFindStatementOf(const QString &fileName, const QString &
 }
 
 
-PStatement CppParser::findStatementOf(const QString &fileName, const QStringList &expression, const PStatement &currentScope)
+PStatement CppParser::findStatementOf(const QString &fileName, const QStringList &expression, const PStatement &currentScope) const
 {
     QMutexLocker locker(&mMutex);
     if (mParsing)
@@ -588,7 +588,7 @@ PStatement CppParser::doFindStatementOf(const QString &fileName, const QStringLi
 
 }
 
-PStatement CppParser::findStatementOf(const QString &fileName, const QStringList &expression, int line)
+PStatement CppParser::findStatementOf(const QString &fileName, const QStringList &expression, int line) const
 {
     QMutexLocker locker(&mMutex);
     if (mParsing)
@@ -610,7 +610,7 @@ PStatement CppParser::doFindStatementOf(const QString &fileName, const QStringLi
     return statement;
 }
 
-PStatement CppParser::findAliasedStatement(const PStatement &statement)
+PStatement CppParser::findAliasedStatement(const PStatement &statement) const
 {
     QMutexLocker locker(&mMutex);
     if (mParsing)
@@ -618,7 +618,7 @@ PStatement CppParser::findAliasedStatement(const PStatement &statement)
     return doFindAliasedStatement(statement);
 }
 
-QList<PStatement> CppParser::listTypeStatements(const QString &fileName, int line)
+QList<PStatement> CppParser::listTypeStatements(const QString &fileName, int line) const
 {
     QMutexLocker locker(&mMutex);
     if (mParsing)
@@ -764,7 +764,7 @@ PStatement CppParser::findStatementStartingFrom(const QString &fileName, const Q
     return PStatement();
 }
 
-PStatement CppParser::findTypeDefinitionOf(const QString &fileName, const QString &aType, const PStatement& currentClass)
+PStatement CppParser::findTypeDefinitionOf(const QString &fileName, const QString &aType, const PStatement& currentClass) const
 {
     QMutexLocker locker(&mMutex);
 
@@ -774,7 +774,7 @@ PStatement CppParser::findTypeDefinitionOf(const QString &fileName, const QStrin
     return doFindTypeDefinitionOf(fileName,aType,currentClass);
 }
 
-PStatement CppParser::findTypeDef(const PStatement &statement, const QString &fileName)
+PStatement CppParser::findTypeDef(const PStatement &statement, const QString &fileName) const
 {
     QMutexLocker locker(&mMutex);
 
@@ -803,7 +803,7 @@ bool CppParser::freeze(const QString &serialId)
     return true;
 }
 
-QStringList CppParser::getClassesList()
+QStringList CppParser::getClassesList() const
 {
     QMutexLocker locker(&mMutex);
 
@@ -825,7 +825,7 @@ QStringList CppParser::getClassesList()
     return list;
 }
 
-QStringList CppParser::getFileDirectIncludes(const QString &filename)
+QStringList CppParser::getFileDirectIncludes(const QString &filename) const
 {
     QMutexLocker locker(&mMutex);
     if (mParsing)
@@ -858,13 +858,13 @@ QSet<QString> CppParser::internalGetIncludedFiles(const QString &filename) const
     return list;
 }
 
-QSet<QString> CppParser::getIncludedFiles(const QString &filename)
+QSet<QString> CppParser::getIncludedFiles(const QString &filename) const
 {
     QMutexLocker locker(&mMutex);
     return internalGetIncludedFiles(filename);
 }
 
-QSet<QString> CppParser::getFileUsings(const QString &filename)
+QSet<QString> CppParser::getFileUsings(const QString &filename) const
 {
     QMutexLocker locker(&mMutex);
     return internalGetFileUsings(filename);
@@ -894,7 +894,7 @@ QSet<QString> CppParser::internalGetFileUsings(const QString &filename) const
     return result;
 }
 
-QString CppParser::getHeaderFileName(const QString &relativeTo, const QString &headerName, bool fromNext)
+QString CppParser::getHeaderFileName(const QString &relativeTo, const QString &headerName, bool fromNext) const
 {
     QMutexLocker locker(&mMutex);
     QString currentDir = includeTrailingPathDelimiter(extractFileDir(relativeTo));
@@ -927,7 +927,7 @@ QString CppParser::getHeaderFileName(const QString &relativeTo, const QString &h
                                projectIncludes);
 }
 
-bool CppParser::isLineVisible(const QString &fileName, int line)
+bool CppParser::isLineVisible(const QString &fileName, int line) const
 {
     QMutexLocker locker(&mMutex);
     if (mParsing) {
@@ -955,7 +955,7 @@ void CppParser::invalidateFile(const QString &fileName)
     mParsing = false;
 }
 
-bool CppParser::isIncludeLine(const QString &line)
+bool CppParser::isIncludeLine(const QString &line) const
 {
     QString trimmedLine = line.trimmed();
     if ((trimmedLine.length() > 0)
@@ -966,7 +966,7 @@ bool CppParser::isIncludeLine(const QString &line)
     return false;
 }
 
-bool CppParser::isIncludeNextLine(const QString &line)
+bool CppParser::isIncludeNextLine(const QString &line) const
 {
     QString trimmedLine = line.trimmed();
     if ((trimmedLine.length() > 0)
@@ -977,13 +977,13 @@ bool CppParser::isIncludeNextLine(const QString &line)
     return false;
 }
 
-bool CppParser::isProjectHeaderFile(const QString &fileName)
+bool CppParser::isProjectHeaderFile(const QString &fileName) const
 {
     QMutexLocker locker(&mMutex);
     return ::isSystemHeaderFile(fileName,mPreprocessor.projectIncludePaths());
 }
 
-bool CppParser::isSystemHeaderFile(const QString &fileName)
+bool CppParser::isSystemHeaderFile(const QString &fileName) const
 {
     QMutexLocker locker(&mMutex);
     return ::isSystemHeaderFile(fileName,mPreprocessor.includePaths());
@@ -1188,7 +1188,7 @@ void CppParser::unFreeze()
     mLockCount--;
 }
 
-bool CppParser::fileScanned(const QString &fileName)
+bool CppParser::fileScanned(const QString &fileName) const
 {
     QMutexLocker locker(&mMutex);
     if (mParsing)
@@ -1196,7 +1196,7 @@ bool CppParser::fileScanned(const QString &fileName)
     return mPreprocessor.fileScanned(fileName);
 }
 
-bool CppParser::isFileParsed(const QString &filename)
+bool CppParser::isFileParsed(const QString &filename) const
 {
     return mPreprocessor.fileScanned(filename);
 }
@@ -1214,7 +1214,7 @@ QString CppParser::getScopePrefix(const PStatement& statement) const{
     }
 }
 
-QString CppParser::prettyPrintStatement(const PStatement& statement, const QString& filename, int line)
+QString CppParser::prettyPrintStatement(const PStatement& statement, const QString& filename, int line) const
 {
     QString result;
     switch(statement->kind) {
diff --git a/RedPandaIDE/parser/cppparser.h b/RedPandaIDE/parser/cppparser.h
index 99aba6d6..6c9d40c3 100644
--- a/RedPandaIDE/parser/cppparser.h
+++ b/RedPandaIDE/parser/cppparser.h
@@ -56,38 +56,38 @@ public:
     void clearProjectFiles();
     QList<PStatement> getListOfFunctions(const QString& fileName,
                              const QString& phrase,
-                             int line);
-    PStatement findScopeStatement(const QString& filename, int line);
-    PParsedFileInfo findFileInfo(const QString &filename);
+                             int line) const;
+    PStatement findScopeStatement(const QString& filename, int line) const;
+    PParsedFileInfo findFileInfo(const QString &filename) const;
     QString findFirstTemplateParamOf(const QString& fileName,
                                      const QString& phrase,
-                                     const PStatement& currentScope);
+                                     const PStatement& currentScope) const;
     QString findTemplateParamOf(const QString& fileName,
                                      const QString& phrase,
                                      int index,
-                                     const PStatement& currentScope);
+                                     const PStatement& currentScope) const;
     PStatement findFunctionAt(const QString& fileName,
-                            int line);
+                            int line) const;
     int findLastOperator(const QString& phrase) const;
-    PStatementList findNamespace(const QString& name); // return a list of PSTATEMENTS (of the namespace)
-    PStatement findStatement(const QString& fullname);
+    PStatementList findNamespace(const QString& name) const; // return a list of PSTATEMENTS (of the namespace)
+    PStatement findStatement(const QString& fullname) const;
     PStatement findStatementOf(const QString& fileName,
                                const QString& phrase,
-                               int line);
+                               int line) const;
     PStatement findStatementOf(const QString& fileName,
                                const QString& phrase,
                                const PStatement& currentScope,
-                               PStatement& parentScopeType);
+                               PStatement& parentScopeType) const;
 
     PStatement findStatementOf(const QString& fileName,
                                const QStringList& expression,
-                               const PStatement& currentScope);
+                               const PStatement& currentScope) const;
     PStatement findStatementOf(const QString& fileName,
                                const QStringList& expression,
-                               int line);
-    PStatement findAliasedStatement(const PStatement& statement);
+                               int line) const;
+    PStatement findAliasedStatement(const PStatement& statement) const;
 
-    QList<PStatement> listTypeStatements(const QString& fileName,int line);
+    QList<PStatement> listTypeStatements(const QString& fileName,int line) const;
 
     /**
      * @brief evaluate the expression
@@ -98,27 +98,27 @@ public:
      */
     PEvalStatement evalExpression(const QString& fileName,
                                QStringList& expression,
-                               const PStatement& currentScope);
+                               const PStatement& currentScope) const;
     PStatement findTypeDefinitionOf(const QString& fileName,
                                     const QString& aType,
-                                    const PStatement& currentClass);
+                                    const PStatement& currentClass) const;
     PStatement findTypeDef(const PStatement& statement,
-                          const QString& fileName);
+                          const QString& fileName) const;
     bool freeze();  // Freeze/Lock (stop reparse while searching)
     bool freeze(const QString& serialId);  // Freeze/Lock (stop reparse while searching)
-    QStringList getClassesList();
-    QStringList getFileDirectIncludes(const QString& filename);
-    QSet<QString> getIncludedFiles(const QString& filename);
-    QSet<QString> getFileUsings(const QString& filename);
+    QStringList getClassesList() const;
+    QStringList getFileDirectIncludes(const QString& filename) const;
+    QSet<QString> getIncludedFiles(const QString& filename) const;
+    QSet<QString> getFileUsings(const QString& filename) const;
 
-    QString getHeaderFileName(const QString& relativeTo, const QString& headerName, bool fromNext=false);// both
+    QString getHeaderFileName(const QString& relativeTo, const QString& headerName, bool fromNext=false) const;
 
     void invalidateFile(const QString& fileName);
-    bool isLineVisible(const QString& fileName, int line);
-    bool isIncludeLine(const QString &line);
-    bool isIncludeNextLine(const QString &line);
-    bool isProjectHeaderFile(const QString& fileName);
-    bool isSystemHeaderFile(const QString& fileName);
+    bool isLineVisible(const QString& fileName, int line) const;
+    bool isIncludeLine(const QString &line) const;
+    bool isIncludeNextLine(const QString &line) const;
+    bool isProjectHeaderFile(const QString& fileName) const;
+    bool isSystemHeaderFile(const QString& fileName) const;
     void parseFile(const QString& fileName, bool inProject,
                    bool onlyIfNotParsed = false, bool updateView = true,
                    std::shared_ptr<CppParser> parserPtr = nullptr);
@@ -127,11 +127,11 @@ public:
     bool parsing() const;
     void resetParser();
     void unFreeze(); // UnFree/UnLock (reparse while searching)
-    bool fileScanned(const QString& fileName);
+    bool fileScanned(const QString& fileName) const;
 
-    bool isFileParsed(const QString& filename);
+    bool isFileParsed(const QString& filename) const;
 
-    QString prettyPrintStatement(const PStatement& statement, const QString& filename, int line = -1);
+    QString prettyPrintStatement(const PStatement& statement, const QString& filename, int line = -1) const;
 
     bool enabled() const;
     void setEnabled(bool newEnabled);
@@ -742,7 +742,7 @@ private:
 #ifdef QT_DEBUG
     int mLastIndex;
 #endif
-    QRecursiveMutex mMutex;
+    mutable QRecursiveMutex mMutex;
     QMap<QString,KeywordType> mCppKeywords;
     QSet<QString> mCppTypeKeywords;
 
diff --git a/RedPandaIDE/parser/cpppreprocessor.h b/RedPandaIDE/parser/cpppreprocessor.h
index 1d2a0962..8cff9282 100644
--- a/RedPandaIDE/parser/cpppreprocessor.h
+++ b/RedPandaIDE/parser/cpppreprocessor.h
@@ -121,7 +121,7 @@ public:
         return mScannedFiles;
     }
 
-    const QSet<QString> &projectIncludePaths() {
+    const QSet<QString> &projectIncludePaths() const {
         return mProjectIncludePaths;
     }
 
diff --git a/RedPandaIDE/widgets/classbrowser.cpp b/RedPandaIDE/widgets/classbrowser.cpp
index 09a34236..068be8dc 100644
--- a/RedPandaIDE/widgets/classbrowser.cpp
+++ b/RedPandaIDE/widgets/classbrowser.cpp
@@ -463,7 +463,7 @@ bool ClassBrowserModel::isScopeStatement(const PStatement &statement)
     }
 }
 
-QModelIndex ClassBrowserModel::modelIndexForStatement(const QString &key)
+QModelIndex ClassBrowserModel::modelIndexForStatement(const QString &key) const
 {
     QMutexLocker locker(&mMutex);
     if (mUpdating)
diff --git a/RedPandaIDE/widgets/classbrowser.h b/RedPandaIDE/widgets/classbrowser.h
index 6ba9dc02..420b909b 100644
--- a/RedPandaIDE/widgets/classbrowser.h
+++ b/RedPandaIDE/widgets/classbrowser.h
@@ -62,7 +62,7 @@ public:
     ProjectClassBrowserType classBrowserType() const;
     void setClassBrowserType(ProjectClassBrowserType newClassBrowserType);
 
-    QModelIndex modelIndexForStatement(const QString& key);
+    QModelIndex modelIndexForStatement(const QString& key) const;
 signals:
     void refreshStarted();
     void refreshEnd();
@@ -86,7 +86,7 @@ private:
     PCppParser mParser;
     bool mUpdating;
     int mUpdateCount;
-    QRecursiveMutex mMutex;
+    mutable QRecursiveMutex mMutex;
     QString mCurrentFile;
     std::shared_ptr<QHash<StatementKind, std::shared_ptr<ColorSchemeItem> > > mColors;
     ProjectClassBrowserType mClassBrowserType;
diff --git a/RedPandaIDE/widgets/codecompletionpopup.h b/RedPandaIDE/widgets/codecompletionpopup.h
index 3ca8953a..331e6ace 100644
--- a/RedPandaIDE/widgets/codecompletionpopup.h
+++ b/RedPandaIDE/widgets/codecompletionpopup.h
@@ -183,7 +183,7 @@ private:
     QSet<QString> mAddedStatements;
     QString mMemberPhrase;
     QString mMemberOperator;
-    QRecursiveMutex mMutex;
+    mutable QRecursiveMutex mMutex;
     std::shared_ptr<QHash<StatementKind, std::shared_ptr<ColorSchemeItem> > > mColors;
     CodeCompletionListItemDelegate* mDelegate;
 
diff --git a/libs/qsynedit/qsynedit/document.cpp b/libs/qsynedit/qsynedit/document.cpp
index 9176a29d..9ebe2c47 100644
--- a/libs/qsynedit/qsynedit/document.cpp
+++ b/libs/qsynedit/qsynedit/document.cpp
@@ -54,7 +54,7 @@ static void listIndexOutOfBounds(int index) {
 
 
 
-int Document::parenthesisLevel(int line)
+int Document::parenthesisLevel(int line) const
 {
     QMutexLocker locker(&mMutex);
     if (line>=0 && line < mLines.size()) {
@@ -63,7 +63,7 @@ int Document::parenthesisLevel(int line)
         return 0;
 }
 
-int Document::bracketLevel(int line)
+int Document::bracketLevel(int line) const
 {
     QMutexLocker locker(&mMutex);
     if (line>=0 && line < mLines.size()) {
@@ -72,7 +72,7 @@ int Document::bracketLevel(int line)
         return 0;
 }
 
-int Document::braceLevel(int line)
+int Document::braceLevel(int line) const
 {
     QMutexLocker locker(&mMutex);
     if (line>=0 && line < mLines.size()) {
@@ -81,7 +81,7 @@ int Document::braceLevel(int line)
         return 0;
 }
 
-int Document::lineWidth(int line)
+int Document::lineWidth(int line) const
 {
     QMutexLocker locker(&mMutex);
     if (line>=0 && line < mLines.size()) {
@@ -92,7 +92,7 @@ int Document::lineWidth(int line)
         return 0;
 }
 
-int Document::lineWidth(int line, const QString &newText)
+int Document::lineWidth(int line, const QString &newText) const
 {
     QMutexLocker locker(&mMutex);
     if (line<0 || line >= mLines.size())
@@ -105,7 +105,7 @@ int Document::lineWidth(int line, const QString &newText)
     }
 }
 
-int Document::blockLevel(int line)
+int Document::blockLevel(int line) const
 {
     QMutexLocker locker(&mMutex);
     if (line>=0 && line < mLines.size()) {
@@ -114,7 +114,7 @@ int Document::blockLevel(int line)
         return 0;
 }
 
-int Document::blockStarted(int line)
+int Document::blockStarted(int line) const
 {
     QMutexLocker locker(&mMutex);
     if (line>=0 && line < mLines.size()) {
@@ -123,7 +123,7 @@ int Document::blockStarted(int line)
         return 0;
 }
 
-int Document::blockEnded(int line)
+int Document::blockEnded(int line) const
 {
     QMutexLocker locker(&mMutex);
     if (line>=0 && line < mLines.size()) {
@@ -135,7 +135,7 @@ int Document::blockEnded(int line)
         return 0;
 }
 
-int Document::maxLineWidth() {
+int Document::maxLineWidth() const {
     QMutexLocker locker(&mMutex);
     if (mIndexOfLongestLine >= 0) {
         return mLines[mIndexOfLongestLine]->width();
@@ -158,7 +158,7 @@ QString Document::lineBreak() const
     return "\n";
 }
 
-SyntaxState Document::getSyntaxState(int line)
+SyntaxState Document::getSyntaxState(int line) const
 {
     QMutexLocker locker(&mMutex);
     if (line>=0 && line < mLines.size()) {
@@ -189,7 +189,7 @@ void Document::addItem(const QString &s)
     endUpdate();
 }
 
-bool Document::getAppendNewLineAtEOF()
+bool Document::getAppendNewLineAtEOF() const
 {
     QMutexLocker locker(&mMutex);
     return mAppendNewLineAtEOF;
@@ -210,7 +210,7 @@ void Document::setSyntaxState(int line, const SyntaxState& state)
     mLines[line]->setSyntaxState(state);
 }
 
-QString Document::getLine(int line)
+QString Document::getLine(int line) const
 {
     QMutexLocker locker(&mMutex);
     if (line<0 || line>=mLines.count()) {
@@ -219,7 +219,7 @@ QString Document::getLine(int line)
     return mLines[line]->lineText();
 }
 
-int Document::getLineGlyphsCount(int line)
+int Document::getLineGlyphsCount(int line) const
 {
     QMutexLocker locker(&mMutex);
     if (line<0 || line>=mLines.count()) {
@@ -237,13 +237,13 @@ int Document::getLineGlyphsCount(int line)
 //     return mLines[index]->glyphStartCharList();
 // }
 
-int Document::count()
+int Document::count() const
 {
     QMutexLocker locker(&mMutex);
     return mLines.count();
 }
 
-QString Document::text()
+QString Document::text() const
 {
     QMutexLocker locker(&mMutex);
     return getTextStr();
@@ -274,7 +274,7 @@ void Document::setContents(const QStringList &text)
     }
 }
 
-QStringList Document::contents()
+QStringList Document::contents() const
 {
     QMutexLocker locker(&mMutex);
     QStringList result;
@@ -332,7 +332,7 @@ void Document::addLines(const QStringList &strings)
     }
 }
 
-int Document::getTextLength()
+int Document::getTextLength() const
 {
     QMutexLocker locker(&mMutex);
     int Result = 0;
@@ -790,13 +790,13 @@ void Document::saveToFile(QFile &file, const QByteArray& encoding,
     }
 }
 
-QString Document::glyph(int line, int glyphIdx)
+QString Document::glyph(int line, int glyphIdx) const
 {
     QMutexLocker locker(&mMutex);
     return mLines[line]->glyph(glyphIdx);
 }
 
-QString Document::glyphAt(int line, int charPos)
+QString Document::glyphAt(int line, int charPos) const
 {
     QMutexLocker locker(&mMutex);
     if (line<0 || line>=count())
@@ -806,7 +806,7 @@ QString Document::glyphAt(int line, int charPos)
     return mLines[line]->glyph(glyphIdx);
 }
 
-int Document::charToGlyphStartChar(int line, int charPos)
+int Document::charToGlyphStartChar(int line, int charPos) const
 {
     QMutexLocker locker(&mMutex);
     if (line<0 || line>=count())
@@ -889,7 +889,7 @@ int GlyphCalculator::stringWidth(const QString &str, int left, const QFontMetric
     return right - left;
 }
 
-int Document::glyphCount(int line)
+int Document::glyphCount(int line) const
 {
     QMutexLocker locker(&mMutex);
     if (line<0 || line>=count())
@@ -897,7 +897,7 @@ int Document::glyphCount(int line)
     return mLines[line]->glyphsCount();
 }
 
-int Document::glyphStartChar(int line, int glyphIdx)
+int Document::glyphStartChar(int line, int glyphIdx) const
 {
     QMutexLocker locker(&mMutex);
     if (line<0 || line>=count())
@@ -905,7 +905,7 @@ int Document::glyphStartChar(int line, int glyphIdx)
     return mLines[line]->glyphStartChar(glyphIdx);
 }
 
-int Document::glyphLength(int line, int glyphIdx)
+int Document::glyphLength(int line, int glyphIdx) const
 {
     QMutexLocker locker(&mMutex);
     if (line<0 || line>=count())
@@ -913,7 +913,7 @@ int Document::glyphLength(int line, int glyphIdx)
     return mLines[line]->glyphLength(glyphIdx);
 }
 
-int Document::glyphStartPostion(int line, int glyphIdx)
+int Document::glyphStartPostion(int line, int glyphIdx) const
 {
     QMutexLocker locker(&mMutex);
     if (line<0 || line>=count())
@@ -921,7 +921,7 @@ int Document::glyphStartPostion(int line, int glyphIdx)
     return mLines[line]->glyphStartPosition(glyphIdx);
 }
 
-int Document::glyphWidth(int line, int glyphIdx)
+int Document::glyphWidth(int line, int glyphIdx) const
 {
     QMutexLocker locker(&mMutex);
     if (line<0 || line>=count())
@@ -929,7 +929,7 @@ int Document::glyphWidth(int line, int glyphIdx)
     return mLines[line]->glyphWidth(glyphIdx);
 }
 
-int Document::charToGlyphIndex(int line, int charIdx)
+int Document::charToGlyphIndex(int line, int charIdx) const
 {
     QMutexLocker locker(&mMutex);
     if (line<0 || line>=count())
@@ -974,7 +974,7 @@ QList<int> GlyphCalculator::calcGlyphPositionList(const QString &lineText, const
     return glyphPostionList;
 }
 
-int Document::xposToGlyphIndex(int line, int xpos)
+int Document::xposToGlyphIndex(int line, int xpos) const
 {
     QMutexLocker locker(&mMutex);
     if (line<0 || line>=count())
@@ -996,7 +996,7 @@ int Document::xposToGlyphIndex(int strWidth, QList<int> glyphPositionList, int x
     // return glyphPositionList.length()-1;
 }
 
-int Document::charToGlyphStartPosition(int line, int charPos)
+int Document::charToGlyphStartPosition(int line, int charPos) const
 {
     QMutexLocker locker(&mMutex);
     if (line<0 || line>=count())
@@ -1006,7 +1006,7 @@ int Document::charToGlyphStartPosition(int line, int charPos)
     return mLines[line]->glyphStartPosition(glyphIdx);
 }
 
-int Document::xposToGlyphStartChar(int line, int xpos)
+int Document::xposToGlyphStartChar(int line, int xpos) const
 {
     QMutexLocker locker(&mMutex);
     if (line<0 || line>=count())
@@ -1016,7 +1016,7 @@ int Document::xposToGlyphStartChar(int line, int xpos)
     return mLines[line]->glyphStartChar(glyphIdx);
 }
 
-int Document::charToGlyphStartPosition(int line, const QString newStr, int charPos)
+int Document::charToGlyphStartPosition(int line, const QString newStr, int charPos) const
 {
     QMutexLocker locker(&mMutex);
     if (line>=0 && line<count() && mLines[line]->lineText() == newStr) {
@@ -1033,7 +1033,7 @@ int Document::charToGlyphStartPosition(int line, const QString newStr, int charP
     }
 }
 
-int Document::xposToGlyphStartChar(int line, const QString newStr, int xpos)
+int Document::xposToGlyphStartChar(int line, const QString newStr, int xpos) const
 {
     QMutexLocker locker(&mMutex);
     if (line<0 || line>=count())
@@ -1233,7 +1233,7 @@ int Document::getLineWidth(int line)
     return mLines[line]->mWidth;
 }
 
-NewlineType Document::getNewlineType()
+NewlineType Document::getNewlineType() const
 {
     QMutexLocker locker(&mMutex);
     return mNewlineType;
@@ -1245,7 +1245,7 @@ void Document::setNewlineType(const NewlineType &fileEndingType)
     mNewlineType = fileEndingType;
 }
 
-bool Document::empty()
+bool Document::empty() const
 {
     QMutexLocker locker(&mMutex);
     return mLines.count()==0;
diff --git a/libs/qsynedit/qsynedit/document.h b/libs/qsynedit/qsynedit/document.h
index df2b0ba0..cb4ae6df 100644
--- a/libs/qsynedit/qsynedit/document.h
+++ b/libs/qsynedit/qsynedit/document.h
@@ -295,7 +295,7 @@ public:
      * @param line line index (starts from 0)
      * @return
      */
-    int parenthesisLevel(int line);
+    int parenthesisLevel(int line) const;
 
     /**
      * @brief get nesting level of brackets at the end of the specified line
@@ -305,7 +305,7 @@ public:
      * @param line line index (starts from 0)
      * @return
      */
-    int bracketLevel(int line);
+    int bracketLevel(int line) const;
 
     /**
      * @brief get nesting level of braces at the end of the specified line
@@ -315,7 +315,7 @@ public:
      * @param line line index (starts from 0)
      * @return
      */
-    int braceLevel(int line);
+    int braceLevel(int line) const;
 
     /**
      * @brief get width of the specified line
@@ -325,7 +325,7 @@ public:
      * @param line line index (starts frome 0)
      * @return
      */
-    int lineWidth(int line);
+    int lineWidth(int line) const;
 
     /**
      * @brief get width of the specified text / line
@@ -340,7 +340,7 @@ public:
      * @param newText the new text
      * @return
      */
-    int lineWidth(int line, const QString &newText);
+    int lineWidth(int line, const QString &newText) const;
 
     /**
      * @brief get block (indent) level of the specified line
@@ -350,21 +350,21 @@ public:
      * @param line line index (starts frome 0)
      * @return
      */
-    int blockLevel(int line);
+    int blockLevel(int line) const;
 
     /**
      * @brief get count of new blocks (indent) started on the specified line
      * @param line line index (starts frome 0)
      * @return
      */
-    int blockStarted(int line);
+    int blockStarted(int line) const;
 
     /**
      * @brief get count of blocks (indent) ended on the specified line
      * @param line line index (starts frome 0)
      * @return
      */
-    int blockEnded(int line);
+    int blockEnded(int line) const;
 
     /**
      * @brief get index of the longest line (has the max width)
@@ -373,7 +373,7 @@ public:
      *
      * @return
      */
-    int maxLineWidth();
+    int maxLineWidth() const;
 
     /**
      * @brief get line break of the current document
@@ -390,7 +390,7 @@ public:
      * @param line line index (starts frome 0)
      * @return
      */
-    SyntaxState getSyntaxState(int line);
+    SyntaxState getSyntaxState(int line) const;
 
     /**
      * @brief set state of the syntax highlighter after parsing the specified line.
@@ -410,7 +410,7 @@ public:
      * @param line line index (starts frome 0)
      * @return
      */
-    QString getLine(int line);
+    QString getLine(int line) const;
 
     /**
      * @brief get count of the glyphs on the specified line.
@@ -420,7 +420,7 @@ public:
      * @param line line index (starts frome 0)
      * @return
      */
-    int getLineGlyphsCount(int line);
+    int getLineGlyphsCount(int line) const;
 
     // /**
     //  * @brief get position list of the glyphs on the specified line.
@@ -440,7 +440,7 @@ public:
      *
      * @return
      */
-    int count();
+    int count() const;
 
     /**
      * @brief get all the text in the document.
@@ -450,7 +450,7 @@ public:
      *
      * @return
      */
-    QString text();
+    QString text() const;
 
     /**
      * @brief set the text of the document
@@ -478,7 +478,7 @@ public:
      *
      * @return
      */
-    QStringList contents();
+    QStringList contents() const;
 
     void putLine(int index, const QString& s, bool notify=true);
 
@@ -488,7 +488,7 @@ public:
     int addLine(const QString& s);
     void addLines(const QStringList& strings);
 
-    int getTextLength();
+    int getTextLength() const;
     void clear();
     void deleteAt(int index);
     void deleteLines(int index, int numLines);
@@ -500,17 +500,17 @@ public:
     void saveToFile(QFile& file, const QByteArray& encoding,
                     const QByteArray& defaultEncoding, QByteArray& realEncoding);
 
-    QString glyph(int line, int glyphIdx);
-    QString glyphAt(int line, int charPos);
+    QString glyph(int line, int glyphIdx) const;
+    QString glyphAt(int line, int charPos) const;
 
     int stringWidth(const QString &str, int left) const {
         return mGlyphCalculator.stringWidth(str, left);
     }
 
-    int charToGlyphStartChar(int line, int charPos);
+    int charToGlyphStartChar(int line, int charPos) const;
     //int columnToGlyphStartColumn(int line, int charPos);
 
-    int glyphCount(int line);
+    int glyphCount(int line) const;
     /**
      * @brief get start index of the chars representing the specified glyph in the specified line.
      *
@@ -520,7 +520,7 @@ public:
      * @param glyphIdx index of the glyph in the line (starting from 0)
      * @return char index in the line text (start from 0)
      */
-    int glyphStartChar(int line, int glyphIdx);
+    int glyphStartChar(int line, int glyphIdx) const;
 
     /**
      * @brief get count of the chars representing the specified glyph in the specified line.
@@ -531,7 +531,7 @@ public:
      * @param glyphIdx index of the glyph in the line (starting from 0)
      * @return
      */
-    int glyphLength(int line, int glyphIdx);
+    int glyphLength(int line, int glyphIdx) const;
 
     /**
      * @brief get start column of the specified glyph in the specified line.
@@ -542,7 +542,7 @@ public:
      * @param glyphIdx index of the glyph in the line (starting from 0)
      * @return the column (starting from 1)
      */
-    int glyphStartPostion(int line, int glyphIdx);
+    int glyphStartPostion(int line, int glyphIdx) const;
 
     /**
      * @brief get width (in columns) of the specified glyph in the specified line.
@@ -553,7 +553,7 @@ public:
      * @param glyphIdx index of the glyph in the line (starting from 0)
      * @return
      */
-    int glyphWidth(int line, int glyphIdx);
+    int glyphWidth(int line, int glyphIdx) const;
 
     int glyphWidth(const QString &glyph, int left) const {
         return mGlyphCalculator.glyphWidth(glyph,left);
@@ -568,7 +568,7 @@ public:
      * @param charIdx position of the char in the line text (starting from 0)
      * @return glyph index in the line (starting from 0)
      */
-    int charToGlyphIndex(int line, int charPos);
+    int charToGlyphIndex(int line, int charPos) const;
 
     /**
      * @brief get index of the glyph displayed on the specified column
@@ -579,20 +579,20 @@ public:
      * @param column the column (starting from 1)
      * @return glyph index in the line (starting from 0)
      */
-    int xposToGlyphIndex(int line, int xpos);
+    int xposToGlyphIndex(int line, int xpos) const;
 
-    int charToGlyphStartPosition(int line, int charPos);
-    int xposToGlyphStartChar(int line, int xpos);
-    int charToGlyphStartPosition(int line, const QString newStr, int charPos);
-    int xposToGlyphStartChar(int line, const QString newStr, int xpos);
+    int charToGlyphStartPosition(int line, int charPos) const;
+    int xposToGlyphStartChar(int line, int xpos) const;
+    int charToGlyphStartPosition(int line, const QString newStr, int charPos) const;
+    int xposToGlyphStartChar(int line, const QString newStr, int xpos) const;
 
-    bool getAppendNewLineAtEOF();
+    bool getAppendNewLineAtEOF() const;
     void setAppendNewLineAtEOF(bool appendNewLineAtEOF);
 
-    NewlineType getNewlineType();
+    NewlineType getNewlineType() const;
     void setNewlineType(const NewlineType &fileEndingType);
 
-    bool empty();
+    bool empty() const;
 
     int tabSize() const { return mGlyphCalculator.tabSize(); }
 
@@ -662,7 +662,7 @@ private:
 
     int mSetLineWidthLockCount;
     bool mMaxLineChangedInSetLinesWidth;
-    QRecursiveMutex mMutex;
+    mutable QRecursiveMutex mMutex;
 
     GlyphCalculator mGlyphCalculator;