Interferences by using QQuickFramebufferObject and QQuickPaintedItem

PowerNow

Hi,
I'm using Qml with e.g two items. The first consists a QQuickFramebufferObject and the second a QQuickPaintedItem. The QQuickFramebufferObject renders a terrain and by pressing on it the perspective angle is changing.

...
Item {
     id: iFrameBuffer
      anchors.fill: parent
              
      Render {
         anchors.fill: parent
         mirrorVertically: true

         MouseArea {
             anchors.fill: parent

             onClicked: parent.setAngle(0)
         }
     }
}

DCross {
   id: iCross
   width: parent.width * 0.28
   height: width
   anchors.centerIn: parent

}
...

If I set in DCross in C++

setRenderTarget(QQuickPaintedItem::FramebufferObject);

it comes to undesirable behavior.

win10: the app crashes
android:
After pressing multiple times on it to recalculate the terrain with different perspective angles the QQuickFramebufferObject does not correctly display the terrain (looks like visually disorders/flickers).

Using

setRenderTarget(QQuickPaintedItem::Image);

everything works fine.

My question is now, is it possible that both items interfere because they maybe use the same framebuffer? Is there a special command for the QQuickFramebufferObject?

Here a short version of the C++ part of the QQuickFramebufferObject

Rend::Rend()
{
    m_func = QOpenGLContext::currentContext()->functions();
    m_func->initializeOpenGLFunctions();

    m_func->glEnable(GL_DEPTH_TEST);
    m_func->glEnable(GL_CULL_FACE);
    m_func->glFrontFace(GL_CCW);
    m_func->glClearColor(0, 0, 0, 1);

    m_shaderProgram.addShaderFromSourceFile(QOpenGLShader::Vertex, ":/shd/vert.vsh");
    m_shaderProgram.addShaderFromSourceFile(QOpenGLShader::Fragment, ":/shd/frag.fsh");
    m_shaderProgram.link();
    m_shaderProgram.bind();

    ...
}

QOpenGLFramebufferObject* Rend::createFramebufferObject(const QSize &size) 
{   
    QOpenGLFramebufferObjectFormat format;
    format.setAttachment(QOpenGLFramebufferObject::CombinedDepthStencil);
    format.setSamples(0);
    
    return new QOpenGLFramebufferObject(size, format);
}

void Rend::render()
{
    ...

    m_shaderProgram.bind();

    int mvpMatrixLoc = m_shaderProgram.uniformLocation("mvpMatrix");
    int colorLoc = m_shaderProgram.uniformLocation("color");
    m_shaderProgram.setUniformValue(mvpMatrixLoc, m_pMatrix * vMatrix * mMatrix);
    m_shaderProgram.setUniformValue(colorLoc, QColor(Qt::white));

    m_func->glClearColor(0, 0, 0, 1);
    m_func->glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    m_geom->draw(&m_shaderProgram);

    m_shaderProgram.release();

    m_window->resetOpenGLState();
}

void Rend::synchronize(QQuickFramebufferObject *item)

{
    m_fbo = static_cast<Fbo *>(item);

    m_window = m_fbo->window();

    m_alpha = m_fbo->angle();
}

Thxs in andvance...