bug of QMdiArea showing scrollbar ?

QtTester

Hei, guys.
I have a MainWindow project from 'new project wizard'.
VS2019+5.15.2+Win7
Here is my code:

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    m_mdiArea = new QMdiArea(this);
    m_mdiArea->setHorizontalScrollBarPolicy(Qt::ScrollBarAsNeeded);
    m_mdiArea->setVerticalScrollBarPolicy(Qt::ScrollBarAsNeeded);
    setCentralWidget(m_mdiArea);

    QMenu *mu = new QMenu("test");
    QAction *a = new QAction("add widget1");

    mu->addAction(a);
    connect(a,&QAction::triggered,this,[&](){
        auto *w1 = new QWidget;
        auto *b1 = new QPushButton("btn1-1");
        auto *b2 = new QPushButton("btn1-2");
        auto *vlay = new QVBoxLayout;
        auto *sw = new QMdiSubWindow;

        vlay->addWidget(b1);
        vlay->addSpacerItem(new QSpacerItem(20,40,QSizePolicy::Minimum,QSizePolicy::Expanding));
        vlay->addWidget(b2);
        w1->setLayout(vlay);
        w1->resize(500,400);
        w1->setMinimumHeight(400);
        sw->setWidget(w1);
        sw->resize(w1->size());
        m_mdiArea->addSubWindow(sw);
        w1->show();
    });
    a = new QAction("add widget2");
    mu->addAction(a);
    connect(a,&QAction::triggered,this,[&](){
        QWidget *w2 = new QWidget;
        auto *b1 = new QPushButton("btn2-1");
        auto *b2 = new QPushButton("btn2-2");
        auto *vlay = new QVBoxLayout;
        QMdiSubWindow *sw = new QMdiSubWindow;

        vlay->addWidget(b1);
        vlay->addSpacerItem(new QSpacerItem(20,40,QSizePolicy::Minimum,QSizePolicy::Expanding));
        vlay->addWidget(b2);
        w2->setLayout(vlay);
        w2->resize(500,400);
        w2->setMinimumHeight(400);
        sw->setWidget(w2);
        sw->resize(w2->size());
        m_mdiArea->addSubWindow(sw);
        w2->show();
    });
    menuBar()->addMenu(mu);
    resize(650,380);
}

when add a widget, not showing horizon scrollbar from mdiarea(Step1), then click subwindow to show max,the vertical scrollbar shows fine(Step3).
but, if add a widget, and showing horizon scrllbar from mdiarea(Step1), then click subwindow to show max,the vertical scrollbar Will NOT show anymore(Step3).

here is the picture, vbar shows fine:

vbar will not show anymore if we have horizon bar on start:

why? any tips will be appreciated.

Christian Ehrlicher

I can confirm this issue and think it's fixable. For now set the minimum size to sw too.

Christian Ehrlicher

Created a bug report: https://bugreports.qt.io/browse/QTBUG-100494

QtTester

This post is deleted!

Christian Ehrlicher

Merged, will be fixed in Qt6.4.