qtrangeslider doesn't respond to drag properly on macOS 12 with Qt5.15

[sfhbarnett]

Describe the bug
Qtrangeslider is not behaving properly. Dragging one of the handles causes the other handle to disappear (It looks like the slider thinks I have grabbed the top slider when I grab the bottom one). I've attached a video of the behaviour.

To Reproduce
Steps to reproduce the behavior:
The code below can reproduce the behaviour on my computer

    import sys
    from PyQt5 import QtCore, QtWidgets
    from superqt import QRangeSlider
    
    
    class MainWindow(QtWidgets.QMainWindow):
    
        def __init__(self, *args, **kwargs):
            super(MainWindow, self).__init__(*args, **kwargs)
    
            vlayout2 = QtWidgets.QHBoxLayout()
            self.qtr = QRangeSlider(QtCore.Qt.Orientation.Vertical)
            vlayout2.addWidget(self.qtr)
            widget = QtWidgets.QWidget()
            widget.setLayout(vlayout2)
            self.setCentralWidget(widget)
    
    
    def main():
        if not QtWidgets.QApplication.instance():
            app = QtWidgets.QApplication(sys.argv)
        else:
            app = QtWidgets.QApplication.instance()
        app.setQuitOnLastWindowClosed(True)
        main = MainWindow()
        main.show()
        sys.exit(app.exec_())
    
    if __name__ == '__main__':
        m = main()

Expected behavior
Normal slider behaviour

Screenshots

Screen.Recording.2022-03-21.at.09.48.18.mov

Desktop (please complete the following information):

• macOS 12.1
• PyQt5 5.15.6
• superqt 0.3.1
• Python 3.9.7

[tlambert03]

Thanks, I was able to reproduce this on PyQt5-5.15.6 and pyside2-5.15.2.1, but interestingly it works fine on PyQt6-Qt6-6.2.3 and pyside6-6.2.4 ... I went back and this has been there since at least v0.2.0, which is very surprising!
I also happened to be on macOS 12.3 this time, so want to check some other machines to see if this depends on os version too.

thanks for the report!

[tlambert03]

Was not able to reproduce on macOS 10.15 (catalina), so at this point, it appears to be specific to macos >= 11 and Qt < 6

[sfhbarnett]

Ok thanks for the updates! I don't have an issue moving to PyQt6 so that counts as a fix to me.

[tlambert03]

doing some more research on this...
it appears to be a bug with Qt itself on monterey: https://bugreports.qt.io/browse/QTBUG-98093

also described here: https://stackoverflow.com/questions/69890284/qslider-in-qt-misbehaves-in-new-macos-monterey-v12-0-1-any-workaround/69890285#69890285

it also looks like using a custom style sheet can solve it (for example, the styled sliders in the demo widget work fine)... so perhaps we can find a "cheat" solution similar to the SO post above