For the borderless window to work on X11, flags must be reset first

[Hellzed]

Before this, main window title bar still appears on some window managers (eg. GNOME). From what I gather, we need to reset the full set of flags to something customizable with self.setWindowFlags(QtCore.Qt.CustomizeWindowHint) first before setting an individual flag with self.setWindowFlag().
At the moment, I don't have a PC or Mac to check this doesn't cause a regression elsewhere.

[ngld]

Hm... does this work with self.setWindowFlag(QtCore.Qt.CustomizeWindowHint, enabled)?
I think the way you implemented it breaks if a user deactivates the custom titlebar.
Also, please disable your automated error reports if you change anything code related. Receiving those errors only makes sifting through the error reports harder.

[Hellzed]

Sorry for the spam, I nuked my .knossos and forgot it was the default crash report upload.
Actually deactivating the custom title bar was broken before... Qt window flags are weird, but manually resetting the QtCore.Qt.Window works for me when disabling the custom title bar.

[ngld]

Sorry for the later reply. Unfortunately, I can't accept the PyQt5 update since it breaks stuff on Windows for several reasons: a) It has weird bugs in QtWebEngine (selects open in the wrong place) and b) The 32bit version of it no longer ships with 32bit builds.

Can you tell me more about the crash?

[Hellzed]

Here's the bug: https://bugreports.qt.io/browse/QTBUG-66346
It affects series 5.9.4 and 5.10.1... It was fixed in 5.9.5 and 5.11, but not in 5.10 series.
With PyQt, instead of broken rendering, it just crashes.
Workarounds mentioned in the bug comments do help.