Using QPainter and OpenGL together issues

kloveridge

I have been having a moderate of amount of success understanding QT. But I've run into a problem with mixing QPainter and openGL.

I have written just a simple OpenGL renderer that compiles a simple vertex/fragment program. It draws a spinning textured cube. I then wanted to see some QPainter elements be drawn on top of the view and everything has stopped working.

So here's the main rendering code:

@void MainGL::paintEvent(QPaintEvent* event)
{
QPainter painter(this);
painter.beginNativePainting();

glEnable(GL_DEPTH_TEST);
glEnable(GL_CULL_FACE);

// Clear color and depth buffer
qglClearColor(m_bkcolor);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

// Calculate model view transformation
QMatrix4x4 viewMatrix;
viewMatrix.setToIdentity();
viewMatrix.translate(0.0, 0.0, -5.0);
viewMatrix.rotate(m_rotation);

m_program.bind();

m_program.setUniformValue("mvp_matrix", m_projection * viewMatrix);
m_program.setUniformValue("texture", 0);
m_cube.drawCubeGeometry(&m_program);

glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
painter.endNativePainting();

// painter.begin(this);
// painter.setPen(Qt::blue);
// painter.setFont(QFont("Arial", 30));
// painter.drawText(rect(), Qt::AlignCenter, "Hello World!");
// painter.end();
}
@

I've disabled the QPainter code except the painter.beginNativePainting() portion.

My guess is, when I wrap the OpenGL code between the painter.beginNativePainting()/painter.endNativePainting(); that something is happening to my openGL context that I'm not sure what to do.

You will notice I am binding the shader. I know that if this were a full-blown rendering pipeline, I would need to be sure my context was properly maintained. If I comment out the QPainter code, everything draws fine.

What am I missing here?