Using Qpainter in qglwidget paintGL function

hi,

i have problem with overpainting in qglwidget, when i create QPainter p(this) in paintG,L swapbuffers() dont work and my widget blinked during animation using updateGL and give me this error:
QOpenGlContext::swapBuffers called without corresponding makecurrent()
and when i using paintEvent() and i use update() i havent see smooth swap buffer too but if i dont use QPainter its work so good,

How can i use QPainter beside using swapbuffers()? do we have any function fer getting current context painter device?

this is my code

Code:

---

paintGL()
{
     glClearColor(0,0,0,1);
     glClear(GL_COLOR_BUFFER_BIT);
 
     QPainter p(this);
     drawBackground(&p);
     drawForeground();
}

---

sorry for bad english and thanks.