QOpenGLPaintDevice/QPainter doesn't paint in webassembly

#include <memory>
#include <QGuiApplication>
#include <QSurfaceFormat>
#include <QOpenGLContext>
#include <QOpenGLWindow>
#include <QOpenGLPaintDevice>
#include <QPainter>

class GLWindow : public QOpenGLWindow
{
    std::unique_ptr<QOpenGLPaintDevice> m_gl_paint_device;
public:
    void initializeGL() { m_gl_paint_device = std::make_unique<QOpenGLPaintDevice>(); }
    void resizeGL(int w, int h) { m_gl_paint_device->setSize({ w, h }); }
    void paintGL() {
        QPainter painter(m_gl_paint_device.get());
        // QPainter painter(this);  // also does not work and gives the same java script console errors
        painter.setBrush(QBrush(QColor(0xFF0088)));
        painter.drawRect(5, 8, 120, 120);
    }
};

int main(int argc, char *argv[]) {
    QGuiApplication app(argc, argv);
    QSurfaceFormat fmt;
    fmt.setDepthBufferSize(24);

    bool webassembly = false;
    if (QOpenGLContext::openGLModuleType() == QOpenGLContext::LibGL) {
        fmt.setVersion(3, 3);
        fmt.setProfile(QSurfaceFormat::CoreProfile);
    } else {
        fmt.setVersion(3, 0);
        webassembly = true;
    }
    QSurfaceFormat::setDefaultFormat(fmt);

    GLWindow glWindow;
    if (webassembly) glWindow.showFullScreen();
    else glWindow.showMaximized();
    return app.exec();
}