KeyPressEvent without Focus

Question

I am programming a simple GUI, that will open a opencv window at a specific point. This window has some very basic keyEvents to control it. I want to advance this with a few fun

Answer 1

The keyPressEvent method is only invoked if the widget has the focus so if the focus has another application then it will not be notified, so if you want to detect keyboard events then you must handle the OS libraries, but in python they already exist libraries that report those changes as pyinput(python -m pip install pyinput):

import sys

from PyQt5 import QtCore, QtWidgets

from pynput.keyboard import Key, Listener, KeyCode


class KeyMonitor(QtCore.QObject):
    keyPressed = QtCore.pyqtSignal(KeyCode)

    def __init__(self, parent=None):
        super().__init__(parent)
        self.listener = Listener(on_release=self.on_release)

    def on_release(self, key):
        self.keyPressed.emit(key)

    def stop_monitoring(self):
        self.listener.stop()

    def start_monitoring(self):
        self.listener.start()


class MainWindow(QtWidgets.QWidget):
    pass


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

    monitor = KeyMonitor()
    monitor.keyPressed.connect(print)
    monitor.start_monitoring()

    window = MainWindow()
    window.show()

    sys.exit(app.exec_())