How can I check if a keyboard modifier is pressed (Shift, Ctrl, or Alt)?

Question

I am building a UI with Qt Creator and I want buttons to perform different actions with different modifiers. So I thought I could call functions with dynamic string properties that would perform the action depending on the modifier.

Is there a simpler way to do this?

Answer 1

It looks like all you need to do is check the keyboardModifiers in your button handler, and select a different action as appropriate. The various modifiers can be OR'd together in order to check for multi-key combinations:

PyQt5:

import sys
from PyQt5 import QtCore, QtWidgets

class Window(QtWidgets.QWidget):
    def __init__(self):
        super().__init__()
        self.button = QtWidgets.QPushButton('Test')
        self.button.clicked.connect(self.handleButton)
        layout = QtWidgets.QVBoxLayout(self)
        layout.addWidget(self.button)

    def handleButton(self):
        modifiers = QtWidgets.QApplication.keyboardModifiers()
        if modifiers == QtCore.Qt.ShiftModifier:
            print('Shift+Click')
        elif modifiers == QtCore.Qt.ControlModifier:
            print('Control+Click')
        elif modifiers == (QtCore.Qt.ControlModifier |
                           QtCore.Qt.ShiftModifier):
            print('Control+Shift+Click')
        else:
            print('Click')

if __name__ == '__main__':

    app = QtWidgets.QApplication(sys.argv)
    window = Window()
    window.show()
    sys.exit(app.exec())

PyQt4:

import sys
from PyQt4 import QtGui, QtCore

class Window(QtGui.QWidget):
    def __init__(self):
        super(Window, self).__init__()
        self.button = QtGui.QPushButton('Test')
        self.button.clicked.connect(self.handleButton)
        layout = QtGui.QVBoxLayout(self)
        layout.addWidget(self.button)

    def handleButton(self):
        modifiers = QtGui.QApplication.keyboardModifiers()
        if modifiers == QtCore.Qt.ShiftModifier:
            print('Shift+Click')
        elif modifiers == QtCore.Qt.ControlModifier:
            print('Control+Click')
        elif modifiers == (QtCore.Qt.ControlModifier |
                           QtCore.Qt.ShiftModifier):
            print('Control+Shift+Click')
        else:
            print('Click')

if __name__ == '__main__':

    app = QtGui.QApplication(sys.argv)
    window = Window()
    window.show()
    sys.exit(app.exec_())

Answer 2

I was trying to handle multiple keys pressed at the same time (e.g. A and W or W and D). The solution below works with multiple keys being pressed at the same time (including Ctrl, Shift, Alt, etc.).

def keyPressEvent(self, event):
    self.firstrelease = True
    astr = "pressed: " + str(event.key())
    self.keylist.append(astr)

def keyReleaseEvent(self, event):
    if self.firstrelease == True:
        self.processmultikeys(self.keylist)

    self.firstrelease = False
    del self.keylist[-1]

def processmultikeys(self, keyspressed):
    # Your logic here
    print keyspressed

Go here for the original discussion of this solution: How to get multiple key presses in single event?

Answer 3

Here's another approach using bit operators, that avoids getting into many combinations.

@classmethod
def get_key_modifiers(cls):
    QModifiers = Qt.QtWidgets.QApplication.keyboardModifiers()
    modifiers = []
    if (QModifiers & Qt.QtCore.Qt.ShiftModifier) == Qt.QtCore.Qt.ShiftModifier:
        modifiers.append('shift')
    if (QModifiers & Qt.QtCore.Qt.ControlModifier) == Qt.QtCore.Qt.ControlModifier:
        modifiers.append('control')
    if (QModifiers & Qt.QtCore.Qt.AltModifier) == Qt.QtCore.Qt.AltModifier:
        modifiers.append('alt')
    return modifiers