#if QT_VERSION >= 0x050000
#include <QtWidgets>
#else
#include <QtGui>
#endif

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

    QWidget *w = new QWidget;
    QLineEdit *l = new QLineEdit("", w);
    l->setPlaceholderText("type here");
    QPushButton *b = new QPushButton("Ok", w);
    QVBoxLayout *o = new QVBoxLayout(w);
    o->addWidget(l);
    o->addWidget(b);
    w->setLayout(o);
    w->show();
    
    return a.exec();
}