Print contents of X11 events
xev creates a window and then asks the X server to send it events whenever anything happens to the window (such as it being moved, resized, typed in, clicked in, etc.). You can also attach it to an existing window. It is useful for seeing what causes events to occur and to display the information that they contain. It is essentially a debugging and development tool, and should not be needed in normal usage.
To install xev, paste this in macOS terminal after installing MacPorts
sudo port install xev