When showing a maximized frameless window on Windows it covers the full screen. It would be expected that it did not cover the start menu bar.

On Mac it does not cover the dock and it would be expected that the behaviour would be similar on Mac and Windows.

Reproducible with the following example:

#include <QtGui>
#include <QDebug>

int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QWidget w(0, Qt::Window | Qt::FramelessWindowHint );
w.showMaximized();
return app.exec();
}