问如何用网格正确跟踪tkinter中的鼠标事件

EN

import Tkinter as tk

SIZE = 2
root = tk.Tk()

def motion(event):
    x, y = event.x, event.y
    print('{}, {}'.format(x, y))

def create_labels():
    for r in range(SIZE):
        for c in range(SIZE):
            label = tk.Label(root,
                             text="",
                             bg="gray",
                             width=100,
                             height=50,
                             borderwidth=1,
                             font=("Helvetica", 1))

            label.grid(row=r, column=c)

create_labels()
root.bind('<Motion>', motion)
root.mainloop()