add of overline function

mainwindow.h

@@ -30,6 +30,7 @@ public:
     void setItalic();
     void setUnderline();
     void setColor();
+    void setOverline();
 
 private slots:
     void on_pushButton_clicked();
@@ -55,6 +56,8 @@ private slots:
 
     void on_actionColor_triggered();
 
+    void on_actionOverline_triggered();
+
 private:
     Ui::MainWindow *ui;
     QString currentFile;