QtWebEngine flashes when the frameless window is maximized

[myxingkong]

I have a frameless QtWebEngine program that flashes when the focus changes after running on a screen without a taskbar and maximizing the window.

It works fine on a screen with a taskbar.

Following is my test code:

#include <QWidget>
#include <QHBoxLayout>
#include <QApplication>
#include <QWebEngineView>

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QWidget* widget = new QWidget(0);
    widget->setWindowFlags(Qt::FramelessWindowHint);
    QHBoxLayout* lay_parent = new QHBoxLayout;
    QWebEngineView *webView = new QWebEngineView;
    webView->load(QUrl("https://qt.io"));
    widget->show();
    lay_parent->addWidget(webView);
    widget->setLayout(lay_parent);
    widget->showMaximized();
    return app.exec();
}

I tried setting up OpenGL, and it works.
But on some machines the program will fails to run.

QCoreApplication::setAttribute(Qt::AA_UseOpenGLES);

or

QCoreApplication::setAttribute(Qt::AA_UseSoftwareOpenGL);

Is there a better way to stop it from flickering?

This is my test environment:

Operating System: Windows 7, Windows 10

Qt: 5.9.6, 5.12.1

I have two screens, there's no taskbar on the home screen, the taskbar is expanding the screen, and when I run the program on the home screen it's going to trigger a flicker