When a window is maximized and I repeatedly go to full screen and back, after the first or second time the full screen shows some kind of glitch. Suddenly you can see windows 7 window decorations at the side of the window (I'm on windows 10).

The code to reproduce it is attached below. It is just the default QMainWindow application with a function to toggle full screen when the key 'F' is pressed.

The issue can be reproduced as follows:

• Maximize the MainWindow (the maximize button on the top right)
• press F, F, F, F, F to go to full screen, back, and to full screen again and back and to full screen

A screen shot of how it looks on my maschine is attached.

#include "mainwindow.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();

    return a.exec();
}

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QKeyEvent>

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0) : QMainWindow(parent) {}
    ~MainWindow() {}

protected:
    virtual void keyPressEvent( QKeyEvent * event )
    {
        if (event->key() == Qt::Key_F)
        {
            setWindowState(windowState() ^ Qt::WindowFullScreen);
        }
    }
};

#endif // MAINWINDOW_H