How to make a tkinter window Fullscreen on all Displays?

Question

I am working on a program with a window that needs to be fullscreen on all plugged-in Monitors and/or external displays. Is there any way I can do this in Tkinter or do I have to use a different library? So far I have managed to get the window in Fullscreen on my main display but I also need it on the other one(s). This is my code so far:

def create_screencanvas():
    global master_screen
    master_screen = Toplevel(mywindow)
    picture_frame = Frame(master_screen, background = "blue")
    picture_frame.pack(fill=BOTH, expand=YES)

    global screenCanvas
    screenCanvas = Canvas(picture_frame, cursor="cross", bg="grey5")
    screenCanvas.pack(fill=BOTH, expand=YES)

    master_screen.attributes('-fullscreen', True)#Fullscreen on main display but not others
    master_screen.attributes('-alpha', .3)
    master_screen.lift()
    master_screen.attributes("-topmost", True)

mywindow = Tk()
mywindow.title("New Project") 
mywindow.geometry("780x640") 
mywindow.minsize(540, 420) 
mywindow.configure(bg="blue") 

mybtn = Button(text="activate", command=create_screencanvas, cursor="cross")
mybtn.pack() #Button opens the fullscrean window

mywindow.mainloop()

Answer 1

For screenshot taking purposes, you can make your Toplevel window cover all the displays by changing manually its geometry instead of making it fullscreen. So, remove

master_screen.attributes('-fullscreen', True)

and replace it with

w = master_screen.winfo_screenwidth()
h = master_screen.winfo_screenheight()
master_screen.geometry(f"{w}x{h}+0+0")

However, your window now has unwanted decorations. Depending on the OS you are using, you can either use

master_screen.overrideredirect(True)

or, if you are using Linux (in which case, overrideredirect might not allow you to have window transparency),

master_screen.attributes('-type', 'dock')

In both cases, you no longer need

master_screen.attributes("-topmost", True)