videocapture window 未关闭 - OpenCV

Question

Am trying to capture a live video using my webcam.
And the code i learnt from the internet works like a charm.
But there's an issue after i updated my opencv to 4.2.0 that the videoCapture window is not at all closing no matter how many times i try.

Source Code

import numpy as np
import cv2 as cv
cap = cv.VideoCapture(0)
if not cap.isOpened():
    print("Cannot open camera")
    exit()
while True:
    # Capture frame-by-frame
    ret, frame = cap.read()
    frame = cv.flip(frame,1)
    # if frame is read correctly ret is True
    if not ret:
        print("Can't receive frame (stream end?). Exiting ...")
        break
    # Our operations on the frame come here
    gray = cv.cvtColor(frame, cv.COLOR_BGR2GRAY)
    # Display the resulting frame
    cv.imshow('frame', gray)
    if cv.waitKey(1) == ord('q'):
        break
# When everything done, release the capture
cap.release()
cv.destroyAllWindows()

Answer 1

You can add the following at the end of the while loop to detect if the window was closed and terminate the loop:

    if cv.getWindowProperty('frame', cv.WND_PROP_VISIBLE) < 1:
        break

The getWindowProperty will return 0 if the window frame no longer exists.