Use case example for https://codereview.qt-project.org/#/c/236219/

qt-codereview-236219-use-case.cpp

#include <QApplication>

#include <QWidget>
#include <QLineEdit>

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

    QWidget w;
    w.setStyleSheet("background: grey");
    w.setFixedSize(200, 200);

    QLineEdit edit(&w);
    edit.setEchoMode(QLineEdit::Password);
    edit.move(w.rect().center() - edit.rect().center());

    edit.setStyleSheet("background: rgba(255, 255, 255, 0.2); color: white; border: none");

    w.show();

    return a.exec();
}