QMessageBox icon

[penny]

I have a QMessageBox,

MessageBox loadMsgBox;
loadMsgBox.setText("Loading file...");
loadMsgBox.setWindowTitle(" ");
loadMsgBox.setIconPixmap(QPixmap("./icons/icon_loading.gif"));
loadMsgBox.exec();

MessageBox loadMsgBox;
loadMsgBox.setText("Loading file...");
loadMsgBox.setWindowTitle(" ");
loadMsgBox.setIconPixmap(QPixmap("./icons/icon_loading.gif"));
loadMsgBox.exec();

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I want to set the main icon on the title bar, by default it shows a white rectangle. How do i change that?