waitKey function
waits for a pressed key. This function is the only method in OpenCV's HighGUI that can fetch and handle events, so it needs to be called periodically for normal event processing
For further details, please see: http://docs.opencv.org/master/d7/dfc/group__highgui.html#ga5628525ad33f52eab17feebcfba38bd7
Implementation
int waitKey(int delay) => chighgui.cv_waitKey(delay);