I run this example in a jupyter-notebook (python3 with opencv2 version 4.5.3; Firefox under OSX)
import numpy as np
import cv2
img=np.zeros((512,512,3),np.uint8)
img1 = cv2.circle(img,(256,256),63, (0,0,255), -1)
cv2.imshow("Circle",img1)
cv2.waitKey(0)
cv2.destroyAllWindows()
When I select the created popup window and type "0" the window is not destroyed and seems to be freezed (the small colored OSX wheel appears). Any idea ? Thanks