Set display brightness using a slider that works on touch

brightness.py

#!/usr/bin/env python3
# Mostly stolen from https://www.youtube.com/watch?v=ZA_PxLuofV4 / https://learndataanalysis.org/control-lcd-number-widget-with-a-slider-pyqt5-tutorial/
import sys

from PyQt5.QtWidgets import (QApplication, QWidget, QSlider, QHBoxLayout, QDesktopWidget)
from PyQt5.QtCore import Qt

from gi.repository import Gio
from gi.repository import GLib

settings = Gio.Settings('org.mate.power-manager')

b = 0

class AppDemo(QWidget):
    def __init__(self):
        super().__init__()
        self.setWindowFlags(Qt.FramelessWindowHint | Qt.WindowStaysOnTopHint)
        self.resize(50, 50)
        self.setWindowTitle('Brightness control')
        screen = QApplication.primaryScreen()
        availableGeometry = screen.geometry()
        self.setGeometry(availableGeometry.right() - 50, availableGeometry.top(), 50, availableGeometry.height())
        self.setFixedSize(50, availableGeometry.height() )

        sliderB = QSlider(Qt.Vertical)
        sliderB.setMaximum(100)
        sliderB.setMinimum(0)
        sliderB.valueChanged.connect(self.updateB)
        #mouseReleaseEvent = self.slider.mouseReleaseEven
        sliderB.mouseReleaseEvent = self.quit
        style = """
QSlider {
    width: 50px;
}
QSlider::groove:vertical {
    background: #ccc;
    position: absolute;
    left: 0; 
    right: 0;
    top: 0;
}

QSlider::handle:vertical {
    height: 50px;
    width: 50px;
    background: #666;
    margin: 0 -0px;
}
/*
QSlider::add-page:vertical {
    background: #ccc;
}

QSlider::sub-page:vertical {
    background: white;
}
*/
"""
        sliderB.setStyleSheet(style)

        layout = QHBoxLayout()
        layout.addWidget(sliderB)

        sliderB.setValue( int( settings.get_double('brightness-ac' ) ) )
        self.setLayout(layout)

    def updateB(self, event):
        print( "B:" + str( event ) )

        #onAC_Power=comands.getstatus("on_ac_power") == 0 
        settings.set_double('brightness-ac', event )

    def quit(self, event):
        print( "done" )
        sys.exit(0)
        #sys.exit(app.exec_())

if __name__ == '__main__':
    app = QApplication(sys.argv)

    demo = AppDemo()
    demo.show()

    sys.exit(app.exec_())