自定义笔类型和绘图字体

该程序在单独的窗口中绘制和弦和铭文，我需要添加选择字体和阴影样式以绘制和弦的功能，我使用通过按键调用的对话框来执行此操作，我从字体，但在绘制自身时出现错误

这是代码：

import sys
from PyQt5.QtWidgets import QWidget, QApplication, QMainWindow, QPushButton, QLabel, QFontDialog
from PyQt5.QtGui import QPainter, QColor, QPen, QFont
from PyQt5.QtCore import Qt, QRect

class Example(QWidget):

    def __init__(self, mainwindow):
        super().__init__()
        self.mainwindow = mainwindow
        self.initUI()

    def initUI(self):
        self.text = '\u0412\u0020\u043b\u0435\u0432\u043e\u043c\u0020\u043d\u0438\u0436\u043d\u0435\u043c\u0020\u0443\u0433\u043b\u0443\u0020\u043d\u0430\u0440\u0438\u0441\u043e\u0432\u0430\u043d\u0430\u0020\u0445\u043e\u0440\u0434\u0430\u002e'
        self.setGeometry(100, 100, 380, 270)
        self.setWindowTitle('ЛР №3')
        self.show()

    def paintEvent(self, event):
        qp = QPainter()
        qp.begin(self)
        self.drawText(event,qp)
        self.drawChord(qp)
        qp.end()

    def drawText(self, event, qp):
        qp.setPen(QColor(168, 34, 3))
        self.font = self.mainwindow.draw_font
        qp.setFont(self.font)
        qp.drawText(event.rect(), Qt.AlignRight, self.text)

    def drawChord(self, qp):
        pen = QPen(Qt.black, 6, Qt.SolidLine)
        qp.setPen(pen)
        qp.drawChord(0, 200, 320, 140, 30 * 16, 120 * 16)

class window(QMainWindow):
    def __init__(self):
        super().__init__()
        self.resize(565, 232)
        font = QFont()
        font.setPointSize(16)
        self.centralwidget = QWidget()
        self.centralwidget.setObjectName("centralwidget")
        self.label = QLabel(self.centralwidget)
        self.label.setGeometry(QRect(120, 10, 351, 31))
        self.label.setObjectName("label")
        self.label_2 = QLabel(self.centralwidget)
        self.label_2.setGeometry(QRect(120, 55, 391, 25))
        self.label_2.setObjectName("label_2")
        self.label_3 = QLabel(self.centralwidget)
        self.label_3.setGeometry(QRect(120, 90, 361, 31))
        self.label_3.setObjectName("label_3")
        self.pushButton = QPushButton(self.centralwidget)
        self.pushButton.setGeometry(QRect(180, 170, 211, 31))
        self.pushButton.setObjectName("pushButton")
        self.label.setText("Нажмите F1 чтобы выбрать кисть")
        self.label_2.setText("Нажмите F2 чтобы выбрать .txt файл")
        self.label_3.setText("Нажмите F3 чтобы выбрать шрифт")
        self.pushButton.setText("Нарисовать")
        self.label.setFont(font)
        self.label_2.setFont(font)
        self.label_3.setFont(font)
        self.pushButton.setFont(font)
        self.setCentralWidget(self.centralwidget)

        self.pushButton.clicked.connect(self.draw)

        self.draw_font = QFont('Decorative', 10)


    def draw(self):
        self.ex = Example(mainwindow = self)

    def keyPressEvent(self, press):
        if press.key() == Qt.Key_F1:
            pass
        elif press.key() == Qt.Key_F2:
            pass
        elif press.key() == Qt.Key_F3:
            self.draw_font = QFontDialog.getFont()
            print(self.draw_font)

if __name__ == '__main__':

    app = QApplication(sys.argv)
    window = window()
    window.show()
    sys.exit(app.exec_())