qt - Turning WA_TranslucentBackground off stops window repainting

Question

I have a PyQt4.9 window where I would like to toggle the translucency on or off. The reason being is that it sometimes shows a full size phonon video control which doesn't work when the WA_TranslucentBackground attribute is set. (Due to a Qt bug https://bugreports.qt.io/browse/QTBUG-8119)

The problem I have is, after I turn WA_TranslucentBackground attribute back to false, after it has been true, the Window will no longer redraw, so it remains stuck showing the same thing from that point on. Interestingly, click events still respond.

Some example code follows. Click the increment button, and it will update the button text. Click the toggle button and then click the increment button again, and updates no longer show. Clicking the exit button closes the window, showing the events are still responding.

If anyone has any solutions, workarounds or fixes I'd appreciate them. Thanks.

import sys

from PyQt4.QtCore import *
from PyQt4.QtGui import *

class Settings(QWidget):

    def __init__(self, desktop):    
        QWidget.__init__(self)
        self.setAttribute(Qt.WA_TranslucentBackground, True)
        self.setWindowFlags(Qt.FramelessWindowHint)
        self.istransparent = True
        self.count = 0
        self.setWindowTitle("Transparent")
        self.resize(300, 150)
        self.incr_button = QPushButton("Increment")
        toggle_button = QPushButton("Toggle Transparency")
        exit_button = QPushButton("Exit")
        grid = QGridLayout()
        grid.addWidget(self.incr_button, 0, 0)
        grid.addWidget(toggle_button, 1, 0)
        grid.addWidget(exit_button, 2, 0)
        self.setLayout(grid)        
        self.connect(toggle_button, SIGNAL("clicked()"), self.toggle)
        self.connect(self.incr_button, SIGNAL("clicked()"), self.increment)
        self.connect(exit_button, SIGNAL("clicked()"), self.close)

    def increment(self):
        self.count = self.count + 1
        self.incr_button.setText("Increment (%i)" % self.count)

    def toggle(self):
        self.istransparent = not self.istransparent
        self.setAttribute(Qt.WA_TranslucentBackground, self.istransparent)

if __name__ == "__main__":
    app = QApplication(sys.argv)
    s = Settings(app.desktop())
    s.show()
    sys.exit(app.exec_())

Answer 1

Try to replace self.setAttribute(Qt.WA_TranslucentBackground, ...) calls in __init__ and toggle with following method.

def set_transparency(self, enabled):
    if enabled:
        self.setAutoFillBackground(False)
    else:
        self.setAttribute(Qt.WA_NoSystemBackground, False)

    self.setAttribute(Qt.WA_TranslucentBackground, enabled)
    self.repaint()

Tested on PyQt-Py2.7-x86-gpl-4.9-1 (Windows 7)