added proper timecodes in the timeline

ui/timelineheader.h

@@ -2,6 +2,8 @@
 #define TIMELINEHEADER_H
 
 #include <QWidget>
+#include <QFontMetrics>
+class QScrollArea;
 
 class TimelineHeader : public QWidget
 {
@@ -13,7 +15,7 @@ public:
 
 	bool snapping;
 
-	void update_header(double z);
+    void update_header(double z);
 
 protected:
     void paintEvent(QPaintEvent*);
@@ -36,6 +38,8 @@ private:
 
 	void set_playhead(int mouse_x);
 
+    QFontMetrics fm;
+
 signals:
 
 public slots: