Splashscreen doesn't show on Linux

[DmitryArefiev]

Issue type

UI bug

Steps to reproduce

1. Run MS

Screenshots/Screen recordings

In 4.0.2

MuseScore Version

4.2.0 master

Regression

Yes, this used to work in of MuseScore 4.0.2

Operating system

Linux Ubuntu 22.04.3 LTS

Additional context

Splash screen didn't show always in 4.0.2 too, but in 4.1 (and after) it never appears

[pschnittke]

It seems that this bug occurs because Qt does not always immediately issue a paint event after a call is made to show the splash screen:

MuseScore/src/app/app.cpp

Lines 187 to 189 in 88ac0af

	if (splashScreen) {
	splashScreen->show();
	}

Instead, Qt usually issues a paint event only after the splash screen has been deleted, and hence it never appears. I've tried to force Qt to issue a paint event using QWidget::repaint and QCoreApplication::sendEvent with no success, so it seems that the simplest way to fix this would be to add a short delay after splashScreen->show() and follow it up with a call to QCoreApplication::processEvents, like so:

splashScreen->show();
QThread::msleep(100); // Can perhaps be shorter, just need to give the event scheduler some time
app->processEvents(QEventLoop::ExcludeUserInputEvents);

This fix worked on my machine running Fedora 39.

[MarcSabatella]

FWIW, the splash screen works fine in all versions for me on Debian. That's running in a container within ChromeOS, so a non-typical window manager, but still - it indicates the problem isn't as simple as just not working on Linux.