set gl attributes before creating the window, or some of them might be ignored (like vsync on osx); also don't skip some reloads when switching to fullscreen and back; finally did a little code re-organisation
#include <QScrollArea>
#include <QMainWindow>
#include <QLabel>
#include <QListWidget>
#include <QPushButton>
#include "pixlabel.h"
class MyWindow : public QMainWindow
{
Q_OBJECT
public:
MyWindow(QWidget * parent = 0, Qt::WFlags flags = 0);
private:
QScrollArea * sa_xy;
PixLabel * xy;
QPushButton * buttAdd;
QPushButton * buttCode;
QPushButton * buttSave;
QPushButton * buttLoad;
private slots:
void Code();
void Save();
void Load();
};