QML animation blocked when integrating QQuickWidget(QML) and qwidget(VTK) in Python

[ColinZ]

I used QVTKRenderWindowInteractor to integrate VTK in QApplication.
I also use QQuickWidget to load a QML file, which contains few QtQuick Modules, in to the QApplication.
The application can run, and I can get the data from the slider in QML when slider moved.

However, the animation of all modules inside the QML is blocked at first.
I can get the animation back by click the QQuickWidget first, let it gets focus, and then resize the application window or click the screen area outside the application window.
The animation will block again once I click the VTK area.

I had a hard time identifing the problem, can any body help me?

This is the Python file

import sys

from PyQt5 import QtWidgets, QtGui
from vtk.qt.QVTKRenderWindowInteractor import QVTKRenderWindowInteractor
from vtkmodules.vtkFiltersSources import vtkSphereSource
from vtkmodules.vtkRenderingCore import (
    vtkActor,
    vtkPolyDataMapper,
    vtkRenderer
)
from PyQt5.QtQuickWidgets import QQuickWidget
from PyQt5.QtCore import QUrl, QObject, pyqtSlot


def getVTKWidget(parentFrame):
    # Create source
    source = vtkSphereSource()
    source.SetCenter(0, 0, 0)
    source.SetRadius(5.0)
    # Create a mapper
    mapper = vtkPolyDataMapper()
    mapper.SetInputConnection(source.GetOutputPort())
    # Create an actor
    actor = vtkActor()
    actor.SetMapper(mapper)
    ren = vtkRenderer()
    ren.AddActor(actor)
    ren.ResetCamera()

    vtkWidget = QVTKRenderWindowInteractor(parentFrame)
    vtkWidget.GetRenderWindow().AddRenderer(ren)
    vtkWidget.GetRenderWindow().GetInteractor().Initialize()
    vtkWidget.GetRenderWindow().Render()

    return vtkWidget, ren


class my_QQWidget(QQuickWidget):

    def __init__(self):
        super().__init__()
        self.setSource(QUrl.fromLocalFile('./Demo/rect.qml'))

    def focusOutEvent(self, event: QtGui.QFocusEvent) -> None:
        super().focusOutEvent(event)
        print('out')


    def focusInEvent(self, event: QtGui.QFocusEvent) -> None:
        super().focusInEvent(event)
        print('in')
        # print(self.rootObject().findChild(QObject, 'axisComboBox').isFocusScope())
        # print(self.rootObject().findChild(QObject, 'textDegree').isFocusScope())
        # print(self.rootObject().findChild(QObject, 'rectangle').isFocusScope())
        # print(self.rootObject().findChild(QObject, 'angleText').isFocusScope())
        # print(self.rootObject().findChild(QObject, 'resetBtn').isFocusScope())
        # print(self.rootObject().findChild(QObject, 'sliderContainer').isFocusScope())
        # print(self.rootObject().findChild(QObject, 'groove').isFocusScope())
        # print(self.rootObject().findChild(QObject, 'handle').isFocusScope())
        # print(self.rootObject().findChild(QObject, 'slider').isFocusScope())
        self.update()
        self.rootObject().update()
        self.rootObject().updatePolish()
        self.updateGeometry()
        # print(self.focusWidget())
        self.show()
        # print(self.rootObject().hasFocus())
        self.rootObject().polish()


def getQQWidget():
    # qqWidget = QQuickWidget()
    # qqWidget.setSource(QUrl.fromLocalFile('./Demo/rect.qml'))
    qqWidget = my_QQWidget()
    return qqWidget

if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    # main application window
    window = QtWidgets.QMainWindow()
    # QFrame that holds vtk
    vtkframe = QtWidgets.QFrame()
    vl = QtWidgets.QVBoxLayout()
    vtkframe.setLayout(vl)
    # add vtkWidget
    vtkWidget, ren = getVTKWidget(vtkframe)
    vl.addWidget(vtkWidget)

    # QFrame that holds QQuickWidget convert from QML file
    qmlFrame = QtWidgets.QFrame()
    ql = QtWidgets.QVBoxLayout()
    qmlFrame.setLayout(ql)
    # add QQuickWidget (QML file)
    qmlWidget = getQQWidget()
    ql.addWidget(qmlWidget)

    # a slider in QQuickWidget
    slider = qmlWidget.rootObject().findChild(QObject, 'slider')
    # slider moved event
    @pyqtSlot()
    def receive_angle():
        angle = slider.property("value")
        print(f"{angle} Degree")
        can = ren.GetActiveCamera()
        can.Azimuth(5)
        vtkWidget.GetRenderWindow().Render()
    slider.moved.connect(receive_angle)

    # place vtk frame and qml frame in QVBoxLayout
    mainFrame = QtWidgets.QFrame()
    ml = QtWidgets.QVBoxLayout()
    mainFrame.setLayout(ml)
    ml.addWidget(vtkframe)
    ml.addWidget(qmlFrame)

    window.setCentralWidget(mainFrame)
    window.show()

    sys.exit(app.exec_())

And this is the UI, qml file

import QtQuick 2.15
import QtQuick.Controls 2.15
import QtQuick.Timeline 1.0

Item {
    id: applicationwindow
    objectName: "applicationwindow"
    width: 1024
    height: 150

        ComboBox {
            id: comboBox
            objectName: "axisComboBox"
            x: 122
            y: 68
            font.pointSize: 20
            model: ["X Axis", 'Y Axis', 'Z Axis']
            currentIndex: 1
        }

        Text {
            id: text1
            objectName: "textDegree"
            x: 827
            y: 67
            width: 79
            height: 40
            text: qsTr("Degree")
            font.pixelSize: 25
            verticalAlignment: Text.AlignVCenter
        }

        Rectangle {
            id: rectangle
            objectName: "rectangle"
            x: 760
            y: 67
            width: 55
            height: 40
            color: "lightgrey"
            border.color: "grey"

            TextInput {
                id: textEdit
                objectName: "angleText"
                validator: IntValidator {
                    bottom: 0
                    top: 360
                }
                maximumLength: 3
                text: qsTr("0")
                anchors.fill: parent
                font.pixelSize: 26
                horizontalAlignment: Text.AlignRight
                verticalAlignment: Text.AlignVCenter
            }
        }

        Button {
            id: button
            objectName: "resetBtn"
            x: 462
            y: 19
            text: qsTr("Reset")
            font.pixelSize: 26
        }


    Item {
        id: sliderContainer
         objectName: "sliderContainer"
        x: 275
        y: 73
        width: 474
        height: 31
        Image {
            id: sliderContainerAsset
            source: "assets/sliderContainer.png"
        }

        Image {
            id: groove
            objectName: "groove"
            y: 0
            anchors.left: parent.left
            anchors.right: parent.right
            source: "assets/groove.png"
            anchors.leftMargin: 0
            anchors.rightMargin: 0
        }

        Image {
            id: handle
            objectName: "handle"
            x: 444
            y: 1
            anchors.verticalCenter: parent.verticalCenter
            anchors.bottom: parent.bottom
            source: "assets/handle.png"
            anchors.verticalCenterOffset: 0
            anchors.bottomMargin: 0
        }

        Slider {
            id: slider
            objectName: "slider"
            anchors.fill: parent
            value: 0
            stepSize: 1
            to: 180
        }
    }

    Timeline {
        id: timeline
        currentFrame: slider.value
        KeyframeGroup {
            target: handle
            property: "x"
            Keyframe {
                value: 444
                frame: 180
            }

            Keyframe {
                value: 0
                frame: 0
            }
        }
        endFrame: 180
        enabled: true
        startFrame: 0
    }
}

/*##^##
Designer {
    D{i:0;formeditorZoom:0.5}D{i:1}D{i:2}D{i:4}D{i:3}D{i:6}D{i:8}D{i:9}D{i:10}D{i:11}
D{i:7}D{i:12}
}
##^##*/