Why QSplashscreen does not always work?

Question

I\'ve just coded splash screen in my PyQt application, to show an image before start. I\'ve used QSplashscreen. The problem is the image is displayed, let\'s say, once in a

Answer 1

It's because of the sleep(1) line. For QSplashScreen to work properly, there should be an event loop running. However, sleep is blocking. So you don't get to app.exec_() (event loop) part before sleep finishes (for a whole second). That 'gray rectangle' is the case where you enter sleep before QSplashScreen could even paint itself.

For the normal case, you won't have this problem because you'll be waiting within Qt and the event loop will be running. If you want to 'simulate' a wait, sleep for small intervals and force the app to do its job with .processEvents():

# -*- coding: utf-8 -*-
import sys
from time import time, sleep
from PyQt4.QtGui import QApplication, QSplashScreen, QPixmap

from gui.gui import MainWindow

def main():
    app = QApplication(sys.argv)
    start = time() 
    splash = QSplashScreen(QPixmap("aquaticon/images/splash_screen.jpg"))
    splash.show()
    while time() - start < 1:
        sleep(0.001)
        app.processEvents()
    win = MainWindow()
    splash.finish(win)
    win.show()
    app.exec_()

if __name__ == "__main__":
    main()