I am trying to write my own QQuickItems that use the SceneGraph to draw shapes as if it the parent Item was a Canvas. I am using PySide6 and Python. During my attempts I found a bug in PySide6, which was earlier reported. I downloaded the patch that fixed it and it seems to be ok now (https://bugreports.qt.io/browse/PYSIDE-1345).
My program now compiles and runs, but the node is not painted. If I understand the documentation correctly, I need to do three things to have a custom QQuickItem painted:
- Inherit from QQuickItem
- Override updatePaintNode
- Set the ItemHasContents flag
I did all that, registered my type, added it in QML and made sure it has non-zero dimensions. Unfortunately, it still does not get paited. I do not know what to do next.
Here's the minimal working example:
main.py
# This Python file uses the following encoding: utf-8
import os
from pathlib import Path
import sys
from PySide6.QtGui import QGuiApplication, QColor
from PySide6.QtQml import QQmlApplicationEngine, qmlRegisterType
from PySide6.QtQuick import QQuickItem, QSGGeometryNode, QSGGeometry, QSGFlatColorMaterial
class JustItem(QQuickItem):
def __init__(self, parent=None):
super().__init__(parent)
self.setFlag(QQuickItem.ItemHasContents)
def updatePaintNode(self, node, update_data):
if node is None:
node = QSGGeometryNode()
geometry = QSGGeometry(QSGGeometry.defaultAttributes_Point2D(), 4)
geometry.setDrawingMode(QSGGeometry.DrawTriangles)
vertex_data = geometry.vertexDataAsPoint2D()
vertex_data[0].set(10, 10)
vertex_data[1].set(100, 10)
vertex_data[2].set(100, 100)
vertex_data[3].set(10, 100)
material = QSGFlatColorMaterial()
material.setColor(QColor(255, 0, 0, 127))
node.setGeometry(geometry)
node.setMaterial(material)
return node
if __name__ == "__main__":
qmlRegisterType(JustItem, "PythonTypes", 1, 0, "JustItem")
app = QGuiApplication(sys.argv)
engine = QQmlApplicationEngine()
engine.load(os.fspath(Path(__file__).resolve().parent / "main.qml"))
if not engine.rootObjects():
sys.exit(-1)
sys.exit(app.exec())
And QML:
import QtQuick
import QtQuick.Window
import PythonTypes 1.0
Window {
width: 640
height: 480
visible: true
title: qsTr("Hello World")
JustItem {
}
}
The result is an empty white window. When I resize it, it segfaults.
