Disable X close button of cv2.window

edit

Do u meant close window or grayed out X button?

I want to grey out or disable or make disappear the X button in the right corner of the window when the video is displaying

Not in OpenCV. U can do in GUI such as python, Qt, etc.

but if I try to close the window with the button the window will remain always open? it can be only closed with keys via waitkey?

This will close window. Put this at the bottomcv2.destroyAllWindows()

Example, When u press q on keyboard. It will close window.:

    cv2.imshow('frame',gray)
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

# When everything done, release the capture
cap.release()
cv2.destroyAllWindows()