在PyQt中重写QPaintEvents

我正在尝试创建一个文本编辑小部件，它将有一个分隔线。首先，我创建了一个

MyTextEdit

类（作为

QTextEdit

的子类），并重写了它的

paintEvent（）

方法：

import sys
from PyQt4.QtGui import QApplication, QTextEdit, QPainter

class MyTextEdit(QTextEdit):
    """A TextEdit widget derived from QTextEdit and implementing its
       own paintEvent"""

    def paintEvent(self, event):
        painter = QPainter(self)
        painter.drawLine(0, 10, 10, 10)
        QTextEdit.paintEvent(self, event)

app = QApplication(sys.argv)
textEdit = MyTextEdit()
textEdit.show()

sys.exit(app.exec_())

尝试执行此代码时，我收到大量以下错误：

QPainter::begin: Widget painting can only begin as a result of a paintEvent
QPainter::begin: Widget painting can only begin as a result of a paintEvent
...

我做错了什么？

如果一个小部件有一个

painter = QPainter(self.viewport())

---

有趣的是，我不明白为什么那不起作用。那个视口总是把我搞砸。谢谢