Issue with Frameless Window and createWindowContainer Causing UI Not to Refresh on Qt 5.15 (Windows)

yami

I am encountering a problem using Qt 5.15 on the Windows platform. I have created a minimum reproducible example to demonstrate the issue.

The issue arises when I use Qt::FramelessWindowHint and Qt::WA_TranslucentBackground for a frameless window, and then wrap this window with QWidget::createWindowContainer. After doing so, the UI of the frameless window becomes unresponsive and does not refresh properly.|

Here is the code snippet:

#include <QApplication>
#include <QWidget>
#include <QLabel>
#include <QVBoxLayout>
#include <QPalette>
#include <QWindow>
#include <QPushButton>
#include <QDateTime>

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

    QWidget* mainWindow = new QWidget();
    mainWindow->setWindowTitle("Main Window");
    mainWindow->resize(300, 400);

    QPalette pal1;
    pal1.setColor(QPalette::Window, QColor(200, 230, 255));  // Light blue
    mainWindow->setAutoFillBackground(true);
    mainWindow->setPalette(pal1);

    QVBoxLayout* layout1 = new QVBoxLayout(mainWindow);

    QLabel* label1 = new QLabel("Hello, yaminet1024!");
    label1->setAlignment(Qt::AlignCenter);
    layout1->addWidget(label1);

    QWidget* framelessWindow = new QWidget();
    framelessWindow->setWindowFlags(Qt::FramelessWindowHint);
    framelessWindow->setAttribute(Qt::WA_TranslucentBackground);
    framelessWindow->resize(200, 150);

    QVBoxLayout* layout2 = new QVBoxLayout(framelessWindow);
    QLabel* label2 = new QLabel("2025-04-17 17:23:07");
    label2->setAlignment(Qt::AlignCenter);
    layout2->addWidget(label2);

    // Add refresh button
    QPushButton* refreshBtn = new QPushButton("Refresh");
    refreshBtn->setFixedSize(80, 30);
    refreshBtn->setStyleSheet(
        "QPushButton { background: #FFB6C1; border: 1px solid #FF69B4; border-radius: 5px; }"
        "QPushButton:hover { background: #FFC0CB; }"
        "QPushButton:pressed { background: #FF1493; }"
    );

    // Connect button click to update text
    QObject::connect(refreshBtn, &QPushButton::clicked, [label2](){
        QDateTime currentTime = QDateTime::currentDateTime();
        label2->setText(currentTime.toString("yyyy-MM-dd hh:mm:ss"));
    });

    layout2->addWidget(refreshBtn, 0, Qt::AlignHCenter);

    framelessWindow->show();

    QWindow* window = QWindow::fromWinId(framelessWindow->winId());

    QWidget* container = QWidget::createWindowContainer(window, mainWindow);
    container->setMinimumSize(200, 150);
    layout1->addWidget(container);

    mainWindow->show();

    return a.exec();
}

In this example:

The framelessWindow is set with the Qt::FramelessWindowHint and Qt::WA_TranslucentBackground flags.
The frameless window is then wrapped with QWidget::createWindowContainer.
The Refresh button is supposed to update the timestamp shown in the framelessWindow. However, after wrapping the frameless window in createWindowContainer, the UI becomes unresponsive and fails to refresh properly.

I suspect this might be a limitation or a bug related to the use of createWindowContainer with frameless windows using these specific flags.

Has anyone encountered a similar issue or knows of a workaround? Any help is greatly appreciated!

Thank you!

Christian Ehrlicher

I tested it with a recent Qt6 version and could not see any pushbutton at all.