Qt MainWindow Position in Linux

I have a situation where my main window opens in the upper left of the monitor, only under linux. It looks quite strange, especially when a informational popup appears at program start, that is properly centered where mainwindow is on Mac and Windows! Screenshot below:

How can I fix this Linux issue?

You can use setGeometry to position the window in center. It can be like :

#include <QStyle>
#include <QDesktopWidget>

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

    w.setGeometry(QStyle::alignedRect(Qt::LeftToRight, Qt::AlignCenter, w.size(), qApp->desktop()->availableGeometry()));

    w.show();

    return a.exec();
}

An other way :

MainWindow w;

QDesktopWidget *desktop = QApplication::desktop();

int screenWidth = desktop->width();
int screenHeight = desktop->height();

int x = (screenWidth - w.width()) / 2;
int y = (screenHeight - w.height()) / 2;

w.move(x, y);
w.show();