QQuickFramebufferObject

main.qml

import QtQuick 2.3
import Renderer 1.0

Item {
    width: 500
    height: 600

    FBORenderer{
        id: fboRenderItem
        anchors.fill: parent
    }

    Text {
        anchors.bottom: fboRenderItem.bottom
        x: 20
        wrapMode: Text.WordWrap

        text: "This is an openGl rendering with QQuickFrameBufferObject"
    }
}

opengl.py

from PyQt5.QtCore import QUrl, qDebug, QObject
from PyQt5.QtGui import QGuiApplication, QOpenGLFramebufferObjectFormat, QOpenGLFramebufferObject
from PyQt5.QtQml import qmlRegisterType
from PyQt5.QtQuick import QQuickItem, QQuickView, QQuickFramebufferObject


class FbItemRenderer(QQuickFramebufferObject.Renderer):
    def __init__(self, parent=None):
        super(FbItemRenderer, self).__init__()
        qDebug("Creating FbItemRenderer")

    def createFrameBufferObject(self, size):
        qDebug("Creating FrameBufferObject")
        format = QOpenGLFramebufferObjectFormat()
        format.setAttachment(QOpenGLFramebufferObject.Depth)
        return QOpenGLFramebufferObject(size, format)

    def synchronize(self, item):
        qDebug("Synchronizing")

    def render(self):
        qDebug("Render")
        # Called with the FBO bound and the viewport set.
        # ... Issue OpenGL commands.


class FBORenderItem(QQuickFramebufferObject):
    def __init__(self, parent=None):
        qDebug("Create fborenderitem")
        super(FBORenderItem, self).__init__(parent)

    def createRenderer(self):
        qDebug("Create renderer")
        return FbItemRenderer()


if __name__ == '__main__':
    import sys

    app = QGuiApplication(sys.argv)

    qmlRegisterType(FBORenderItem, "Renderer", 1, 0, "FBORenderer")

    view = QQuickView()
    view.setSource(QUrl("main.qml"))
    view.show()

    sys.exit(app.exec_())

Based on the instructions here: Integrating custom OpenGL rendering with Qt Quick via QQuickFramebufferObject

"QQuickFramebufferObject follows the well-known split: subclasses are expected to reimplement a createRenderer() virtual function. This factory function is always called on the scenegraph’s render thread (which is either the main (GUI) thread, or a separate, dedicated one)."

In c++:

• createFrameBufferObject() is called
• render() is called() when something changes in the Item
• synchronize() function called as a result of result of QQuickFramebufferObject::update()