Screen Tearing QOpenGLWidget for 2D Images Drawn with QPainter

Zates

Hi,

I am trying to develop a QT Widgets app, by which I need to rotate large 2D images in real time. When doing so, I see some flickering/tearing of the images when they are moving quickly across the screen.

Currently, I am using a QOpenGLWidget and drawing all the resources in the paintEvent method, and using a timer to call update() to refresh the screen

MyWidget::MyWidget(QWidget *parent) :
    QOpenGLWidget(parent),
    background(":/images/background.png"),
    img1(":/images/resource1.png"),
    img2(":/images/resource2.png")
{
    QTimer *timer = new QTimer(this);
    connect(timer, SIGNAL(timeout()), this, SLOT(update()));
    timer->start(0);
}
void MyWidget::paintEvent(QPaintEvent *event)
{
    if (m_frameCount  == 0) {
         m_time.start();
     }
     m_frameCount++;
     QPainter painter(this);
     painter.drawPixmap(0,0,background);
     painter.setRenderHints(QPainter::Antialiasing | QPainter::SmoothPixmapTransform, true);
     painter.drawPixmap(QPoint(464.0, 20.0), img1);
     QTransform trans;
     trans.translate(960,546);
     trans.rotate(240.0 / 8.0 * m_framecount / 1000.0 % 8000);
     trans.translate(-960, -546);
     painter.setTransform(trans);
     painter.drawImage(QPoint(714,450), img2);
     painter.resetTransform();
     painter.end();
}

I am getting around 30 FPS, I suppose the artifacts are from the refresh rate, is there any way to enable VSync?

I am only drawing many 2D images with a lot of rotations and translations in a from a fixed viewpoint with a fixed background, is there a more efficient way to display these items utilizing OpenGL that will mitigate the artifacts?

Is there a way to cache the background to increase performance?

Thanks for the help!