pyqt marquee text hangs after few hours - python-2.7

Question

I am using following code for creating scrolling text using pyqt. Also I am creating rectangular box in my UI using QPainter. The problem is that the code as such works fine but after sometime it hangs. The message stops scrolling while other part UI is functioning. I used code from earlier stack overflow question for scrolling text Marquee effect. Following is the some part of my code
class MarqueeLabel(QtGui.QLabel):
def __init__(self, parent=None):
QtGui.QLabel.__init__(self, parent)
self.px = 0
self.py = 15
self._direction = Qt.RightToLeft #Qt.LeftToRight
self.setWordWrap(True)
self.timer = QTimer(self)
self.timer.timeout.connect(self.update)
self.timer.start(20)
self._speed = 2
self.textLength = 0
self.fontPointSize = 0
self.setAlignment(Qt.AlignVCenter)
self.setFixedHeight(self.fontMetrics().height())
def setFont(self, font, size):
newfont = QtGui.QFont(font, size, QtGui.QFont.Bold)
QtGui.QLabel.setFont(self, newfont)
self.setFixedHeight(self.fontMetrics().height())
def updateCoordinates(self):
align = self.alignment()
if align == Qt.AlignTop:
self.py = 10
elif align == Qt.AlignBottom:
self.py = self.height() - 10
elif align == Qt.AlignVCenter:
self.py = self.height() / 2
self.fontPointSize = self.font().pointSize() / 2
self.textLength = self.fontMetrics().width(self.text())
def setAlignment(self, alignment):
self.updateCoordinates()
QtGui.QLabel.setAlignment(self, alignment)
def resizeEvent(self, event):
self.updateCoordinates()
QtGui.QLabel.resizeEvent(self, event)
def paintEvent(self, event):
painter = QPainter(self)
if self._direction == Qt.RightToLeft:
self.px -= self.speed()
if self.px <= -self.textLength:
self.px = self.width()
else:
self.px += self.speed()
if self.px >= self.width():
self.px = -self.textLength
painter.drawText(self.px, self.py + self.fontPointSize, self.text())
painter.translate(self.px, 0)
def speed(self):
return self._speed
def setSpeed(self, speed):
self._speed = speed
def setDirection(self, direction):
self._direction = direction
if self._direction == Qt.RightToLeft:
self.px = self.width() - self.textLength
else:
self.px = 0
self.update()
def pause(self):
self.timer.stop()
def unpause(self):
self.timer.start()
class MainWindow(QMainWindow):
def __init__(self, parent=None):
self.signalUpdateUI()
def signalUpdateUI(self):
updateUIThread = Thread(target=self.updateUI)
updateUIThread.daemon = True
updateUIThread.start()
def updateUI(self):
while(1==1):
#update some text color and contents
#update marquee label contents
self.update()
sleep(2)
def paintEvent(self, event):
QWidget.paintEvent(self, event)
painter = QPainter(self)
pen = QtGui.QPen(QtCore.Qt.black, 2, QtCore.Qt.SolidLine)
painter.setPen(pen)
painter.drawLine(0,190, 1920,190)
painter.drawLine(0,300, 1920,300)
painter.drawLine(0,840, 1920,840)
painter.drawLine(0,930, 1920,930)
# Reactangle Box Settings
painter.setPen(self._rectBoxLine_color)
painter.setBrush(self._rectBox_color)
rect = QRect(1430,300,470,535)
painter.drawRect(rect)
painter.setFont(QtGui.QFont('Consolas', 60, QtGui.QFont.Bold))
painter.setPen(QtGui.QColor(0, 0, 0))
painter.drawText(QRect(1430,300,470,535), QtCore.Qt.AlignCenter, self._rect_text)
I don't know why the scrolling message stops after few hours even though the other part UI is functioning.

Answer 1

The implementation of the marqueLabel is efficient so I do not think that is the cause of the error, on the other hand the code that shows is also not executable but what it shows you can notice the misuse of threads for periodic tasks, in the case of the GUI is forbidden to directly modify the GUI from another thread, in addition to the task that is performed is not heavy so you must use a QTimer instead.
from PyQt4 import QtCore, QtGui
class MarqueeLabel(QtGui.QLabel):
def __init__(self, parent=None):
super(MarqueeLabel, self).__init__(parent)
self.px = 0
self.py = 15
self._direction = QtCore.Qt.RightToLeft #Qt.LeftToRight
self.setWordWrap(True)
self.timer = QtCore.QTimer(self, interval=20)
self.timer.timeout.connect(self.update)
self.timer.start()
self._speed = 2
self.textLength = 0
self.fontPointSize = 0
self.setAlignment(QtCore.Qt.AlignVCenter)
self.setFixedHeight(self.fontMetrics().height())
def setFont(self, font, size):
newfont = QtGui.QFont(font, size, QtGui.QFont.Bold)
QtGui.QLabel.setFont(self, newfont)
self.setFixedHeight(self.fontMetrics().height())
def updateCoordinates(self):
align = self.alignment()
if align == QtCore.Qt.AlignTop:
self.py = 10
elif align == QtCore.Qt.AlignBottom:
self.py = self.height() - 10
elif align == QtCore.Qt.AlignVCenter:
self.py = self.height() / 2
self.fontPointSize = self.font().pointSize() / 2
self.textLength = self.fontMetrics().width(self.text())
def setAlignment(self, alignment):
self.updateCoordinates()
QtGui.QLabel.setAlignment(self, alignment)
def resizeEvent(self, event):
self.updateCoordinates()
QtGui.QLabel.resizeEvent(self, event)
def paintEvent(self, event):
painter = QtGui.QPainter(self)
if self._direction == QtCore.Qt.RightToLeft:
self.px -= self.speed()
if self.px <= -self.textLength:
self.px = self.width()
else:
self.px += self.speed()
if self.px >= self.width():
self.px = -self.textLength
painter.drawText(self.px, self.py + self.fontPointSize, self.text())
painter.translate(self.px, 0)
def speed(self):
return self._speed
def setSpeed(self, speed):
self._speed = speed
def setDirection(self, direction):
self._direction = direction
if self._direction == Qt.RightToLeft:
self.px = self.width() - self.textLength
else:
self.px = 0
self.update()
def pause(self):
self.timer.stop()
def unpause(self):
self.timer.start()
class MainWindow(QtGui.QMainWindow):
def __init__(self, parent=None):
super(MainWindow, self).__init__(parent)
self._rectBoxLine_color = QtGui.QColor(QtCore.Qt.green)
self._rectBox_color = QtGui.QBrush(QtCore.Qt.blue)
self._rect_text = "_rect_text"
self.marquee = MarqueeLabel(self)
self.signalUpdateUI()
def signalUpdateUI(self):
timer = QtCore.QTimer(self, interval=2000)
timer.timeout.connect(self.updateUI)
timer.start()
self.updateUI()
def updateUI(self):
#update some text color and contents
#update marquee label contents
self.marquee.setText(QtCore.QDateTime.currentDateTime().toString())
self.update()
def paintEvent(self, event):
super(MainWindow, self).paintEvent(event)
painter = QtGui.QPainter(self)
pen = QtGui.QPen(QtCore.Qt.black, 2, QtCore.Qt.SolidLine)
painter.setPen(pen)
painter.drawLine(0,190, 1920,190)
painter.drawLine(0,300, 1920,300)
painter.drawLine(0,840, 1920,840)
painter.drawLine(0,930, 1920,930)
# Reactangle Box Settings
painter.setPen(self._rectBoxLine_color)
painter.setBrush(self._rectBox_color)
rect = QtCore.QRect(1430,300,470,535)
painter.drawRect(rect)
painter.setFont(QtGui.QFont('Consolas', 60, QtGui.QFont.Bold))
painter.setPen(QtGui.QColor(0, 0, 0))
painter.drawText(QtCore.QRect(1430,300,470,535), QtCore.Qt.AlignCenter, self._rect_text)
if __name__ == '__main__':
import sys
app = QtGui.QApplication(sys.argv)
w = MainWindow()
w.show()
sys.exit(app.exec_())