waitKeyEx

waitKeyEx is a function commonly found in computer vision libraries, most notably OpenCV. Its primary purpose is to introduce a delay into program execution and to capture keyboard input from the user during that delay.

The function typically takes a single argument, which is the duration of the delay in milliseconds. If the argument is set to 0, the function will wait indefinitely until a key is pressed. When a key is pressed, waitKeyEx returns the ASCII value of that key. If no key is pressed within the specified delay, it usually returns -1 or a similar indicator.

This function is frequently used in applications that display images or video streams. By incorporating waitKeyEx, developers can control the frame rate of the displayed content, allowing users to view each frame for a specific period before the next one is shown. It also provides a mechanism for user interaction, such as exiting the program or triggering certain actions based on key presses. For example, a common pattern is to use waitKeyEx(1) within a loop to display video frames, and then check if the pressed key corresponds to an exit command like 'q' or ESC. The "Ex" in waitKeyEx often signifies an extended or enhanced version of a simpler waitKey function, potentially offering additional features or handling different input devices.