Qt keeping mouse centered

Question

I'm wondering if anyone has a trick to keep the mouse position centered in a (QGL)widget for Qt. I read that one could set the mouseposition after finding the delta, but this way works very buggy for me. Mouse events are not properly registered, any if they do, very jumpy.

void World::mouseMoveEvent(QMouseEvent *event)
{
    if (event->buttons() & Qt::LeftButton) {

        GLfloat dx = GLfloat(event->x() - lastPos.x()) / width();
        GLfloat dy = GLfloat(event->y() - lastPos.y()) / height();

        player->rotHorizontal += 360.0 * dx;
        if(player->rotHorizontal < 0.0)
            player->rotHorizontal += 360.0;
        else if(player->rotHorizontal > +360.0)
            player->rotHorizontal -= 360.0;

        player->rotVertical += 360.0 * dy;

        if (player->rotVertical > MAX_ROTATION_UP) {
            player->rotVertical = MAX_ROTATION_UP;
        } else if (player->rotVertical < -MAX_ROTATION_UP) {
            player->rotVertical = -MAX_ROTATION_UP;
        }

    }
//    int diffX = event->pos().x() - lastPos.x() % 20;
//    int diffY = event->pos().y() - lastPos.y() % 20;
//    if (diffY > 10 || diffX > 10 || diffY < -10 || diffX < -10) {
//        QPoint glob = mapToGlobal(QPoint(this->pos().x() + width()/2, this->pos().y() + height()/2));
//        QCursor::setPos(glob);
//    }
    lastPos = event->pos();
    QGLWidget::mouseMoveEvent(event);
}

I commented out the code which would keep the mouse centered. If this would work, I would place it in the leftclick area.

Answer 1

Fixed:

void World::mouseMoveEvent(QMouseEvent *event)
{
    if (event->buttons() & Qt::LeftButton) {

        GLfloat dx = GLfloat(event->x() - lastPos.x()) / width();
        GLfloat dy = GLfloat(event->y() - lastPos.y()) / height();

        player->rotHorizontal += 360.0 * dx;
        if(player->rotHorizontal < 0.0)
            player->rotHorizontal += 360.0;
        else if(player->rotHorizontal > +360.0)
            player->rotHorizontal -= 360.0;

        player->rotVertical += 360.0 * dy;

        if (player->rotVertical > MAX_ROTATION_UP) {
            player->rotVertical = MAX_ROTATION_UP;
        } else if (player->rotVertical < -MAX_ROTATION_UP) {
            player->rotVertical = -MAX_ROTATION_UP;
        }

    }
    QPoint glob = mapToGlobal(QPoint(width()/2,height()/2));
    QCursor::setPos(glob);
    lastPos = QPoint(width()/2,height()/2);
    QGLWidget::mouseMoveEvent(event);
}