QSystemTrayIcon does not go into system tray.

#include <QtGui>
#include <QtWidgets>

int main(int argc, char **argv) {
	QApplication app(argc, argv);
	QIcon icon("/path/to/icon.png");
	QSystemTrayIcon tray(icon);
	QWidget widget;
	widget.setWindowIcon(icon);
	widget.show();
	tray.show();
	return app.exec();
}