Multiple Key Event Bindings in Tkinter - “Control + E” “Command (apple) + E” etc

Question

Mac OS X 10.6.6 - Tkinter

I want to bind multiple-key events, and while I have found an effbot article and the Tk man pages, I\'ve been unable to make this work corr

Answer 1

Option 1

Something like this:

# Status of control, shift and control+shift keys in Python
import tkinter as tk

ctrl = False
shift = False
ctrl_shift = False

def key(event):
    global ctrl, shift, ctrl_shift
    #print(event.keycode, event.keysym, event.state)
    if ctrl_shift:
        print('++{}'.format(event.keysym))
    elif ctrl:
        print('+{}'.format(event.keysym))
    elif shift:
        print('+{}'.format(event.keysym))
    ctrl = False
    shift = False
    ctrl_shift = False

def control_key(state, event=None):
    ''' Controll button is pressed or released '''
    global ctrl
    ctrl = state

def shift_key(state, event=None):
    ''' Controll button is pressed or released '''
    global shift
    shift = state
    control_shift(state)

def control_shift(state):
    ''' + buttons are pressed or released '''
    global ctrl, ctrl_shift
    if ctrl == True and state == True:
        ctrl_shift = True
    else:
        ctrl_shift = False

root = tk.Tk()
root.geometry('256x256+0+0')

root.event_add('<>',  '',   '')
root.event_add('<>', '', '')
root.event_add('<>',    '',     '')
root.event_add('<>',   '',   '')

root.bind('<>', lambda e: control_key(True))
root.bind('<>', lambda e: control_key(False))
root.bind('<>', lambda e: shift_key(True))
root.bind('<>', lambda e: shift_key(False))
root.bind('', key)

root.mainloop()

Option 2

However, in the end, I decided to process keystrokes manually. You can se the example in this file. First, I set keycodes and shortcuts in two dictionaries self.keycode and self.__shortcuts:

# List of shortcuts in the following format: [name, keycode, function]
self.keycode = {}  # init key codes
if os.name == 'nt':  # Windows OS
    self.keycode = {
        'o': 79,
        'w': 87,
        'r': 82,
        'q': 81,
        'h': 72,
        's': 83,
        'a': 65,
    }
else:  # Linux OS
    self.keycode = {
        'o': 32,
        'w': 25,
        'r': 27,
        'q': 24,
        'h': 43,
        's': 39,
        'a': 38,
     }
self.__shortcuts = [['Ctrl+O', self.keycode['o'], self.__open_image],   # 0 open image
                    ['Ctrl+W', self.keycode['w'], self.__close_image],  # 1 close image
                    ['Ctrl+R', self.keycode['r'], self.__roll],         # 2 rolling window
                    ['Ctrl+Q', self.keycode['q'], self.__toggle_poly],  # 3 toggle between roi/hole drawing
                    ['Ctrl+H', self.keycode['h'], self.__open_poly],    # 4 open polygons for the image
                    ['Ctrl+S', self.keycode['s'], self.__save_poly],    # 5 save polygons of the image
                    ['Ctrl+A', self.keycode['a'], self.__show_rect]]    # 6 show rolling window rectangle

Then added self.__keystroke function to monitor keystroke events. This function checks if key is pressed or not:

def __keystroke(self, event):
    """ Language independent handle events from the keyboard """
    #print(event.keycode, event.keysym, event.state)  # uncomment it for debug purposes
    if event.state - self.__previous_state == 4:  # check if  key is pressed
        for shortcut in self.__shortcuts:
            if event.keycode == shortcut[1]:
                shortcut[2]()
    else:  # remember previous state of the event
        self.__previous_state = event.state

Finally, bind the self.__keystroke function to the master GUI window. Note that this function is bonded in the idle mode, because multiple keystrokes slow down the program on weak computers:

# Handle keystrokes in the idle mode, because program slows down on a weak computers,
# when too many key stroke events in the same time.
self.master.bind('', lambda event: self.master.after_idle(self.__keystroke, event))