How do I toggle 'always on top' for a QMainWindow in Qt without causing a flicker or a flash?

Question

void MainWindow::on_actionAlways_on_Top_triggered(bool checked)
{
    Qt::WindowFlags flags = this->windowFlags();
    if (checked)
    {
        this->setWind         


        

Answer 1

Well, for a solution I figured I'd look in the Mono sources, since I know the .NET Form class (System.Windows.Forms) has a TopMost property.

The solution I found for my Qt program was:

void MainWindow::on_actionAlways_on_Top_triggered(bool checked)
{
#ifdef Q_OS_WIN
    // #include 
    if (checked)
    {
        SetWindowPos(this->winId(), HWND_TOPMOST, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE | SWP_NOACTIVATE);
    }
    else
    {
        SetWindowPos(this->winId(), HWND_NOTOPMOST, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE | SWP_NOACTIVATE);
    }
#else
    Qt::WindowFlags flags = this->windowFlags();
    if (checked)
    {
        this->setWindowFlags(flags | Qt::CustomizeWindowHint | Qt::WindowStaysOnTopHint);
        this->show();
    }
    else
    {
        this->setWindowFlags(flags ^ (Qt::CustomizeWindowHint | Qt::WindowStaysOnTopHint));
        this->show();
    }
#endif
}