Add ability to set param of stretch

stretchpanel.h

@@ -3,18 +3,24 @@
 
 #include <QWidget>
 #include <QSlider>
+#include <QComboBox>
 
 class StretchPanel : public QWidget
 {
     Q_OBJECT
     QSlider *m_lowSlider;
     QSlider *m_highSlider;
+    QSlider *m_paramSlider;
+    QComboBox *m_stretchSelect;
 public:
     explicit StretchPanel(QWidget *parent = nullptr);
 signals:
     void lowChanged(int low);
     void highChanged(int high);
     void stretchChanged(int stretch);
+    void paramChanged(float param);
+private slots:
+    void calculateParam();
 };
 
 #endif // STRETCHPANEL_H