Не переносится контент layout

layout->addWidget(&plotzone, 4 );

layout->addWidget(&mpanel, Qt::AlignRight);

void QBoxLayout::addWidget ( QWidget * widget, int stretch = 0, Qt::Alignment alignment = 0 )

layout->addWidget(&plotzone, 4 );

this->setLayout(layout);

    QHBoxLayout * layout = new QHBoxLayout();

    plotzone.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    layout->addWidget(&plotzone, 4);
    layout->addWidget(&mpanel, Qt::AlignRight);
    layout->setMargin(0);

    this->setLayout(layout);

    QPalette Pal(palette());
    Pal.setColor(QPalette::Background, Qt::blue);
    setAutoFillBackground(true);
    setPalette(Pal);

QMainWindow mw;

    NPlotWidget nplot(16);

    mw.setMinimumSize(600, 600);
    mw.setCentralWidget(&nplot);

    mw.show();

 layout->addWidget(&mpanel, Qt::AlignRight);

#include <QApplication>

#include <QWidget>
#include <QHBoxLayout>

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

    QWidget* w1 = new QWidget();
    QWidget* w2 = new QWidget();
    QWidget* w3 = new QWidget();

    w1->setStyleSheet("background-color:red;");
    w2->setStyleSheet("background-color:green;");
    w3->setStyleSheet("background-color:blue;");

    QHBoxLayout *lay = new QHBoxLayout();
    w1->setLayout(lay);
    lay->addWidget(w2);
    lay->addWidget(w3);

    w3->setMinimumSize(100,0);
    w3->setMaximumSize(100,QWIDGETSIZE_MAX);

    w1->show();

    return a.exec();
}