[FIXED] How to overlay QKeyEvents

Issue

This dialog inherits from QMainWindow. Its keyPressEvent() method prints out a message when a combination of Alt + A keys are pressed.

The blue square is QLabel. By an intention it should print the message too but only when Alt + Z keys are pressed. But QMainWindow blocks QLabel's KeyEvents. Even if after the mouse cursor is placed over the blue QLabel hitting Alt + Z triggers no response. Is there a way to overlay or to sum up both widget's events together? So both Alt + Z and Alt + A work?

import sys
from PyQt4 import QtCore, QtGui

class CustomMain(QtGui.QMainWindow):
    def __init__(self, *args, **kwargs):
        QtGui.QMainWindow.__init__(self, *args, **kwargs)
        p = self.palette()
        p.setColor(self.backgroundRole(), QtCore.Qt.red)
        self.setPalette(p)
    def keyPressEvent(self, event):
        if event.modifiers() == QtCore.Qt.AltModifier:
            if event.key() == QtCore.Qt.Key_A:
                print 'QMainWindow: Alt + a'

class Custom(QtGui.QLabel):
    def __init__(self, *args, **kwargs):
        QtGui.QLabel.__init__(self, *args, **kwargs)
        img=QtGui.QImage(64, 64, QtGui.QImage.Format_RGB32)
        img.fill(QtCore.Qt.blue)
        pixmap=QtGui.QPixmap(img)
        self.setPixmap(pixmap)

    def keyPressEvent(self, event):
        if event.modifiers() == QtCore.Qt.AltModifier:
            if event.key() == QtCore.Qt.Key_Z:
                print 'QLabel: Alt + z'

class App(CustomMain):
    def __init__(self, *args, **kwargs):
        CustomMain.__init__(self, *args, **kwargs)
        mainWidget = QtGui.QWidget()

        self.setCentralWidget(mainWidget)
        mainLayout=QtGui.QVBoxLayout()
        mainWidget.setLayout(mainLayout)

        custom=Custom()
        mainLayout.addWidget(custom)

if __name__ == "__main__":
    app = QtGui.QApplication(sys.argv)
    w = App()
    w.show()
    sys.exit(app.exec_())

Solution

You need to propagate the event from QMainWindow to the QLabel:

def keyPressEvent(self, event):
    if event.modifiers() == QtCore.Qt.AltModifier:
        if event.key() == QtCore.Qt.Key_A:
            print 'QMainWindow: Alt + a'
    QtGui.QMainWindow.keyPressEvent(self, event)

Answered By - Daniele Pantaleone