put the altKey into keyState
if the altKey is down then exit mouseUp
repeat until altKey() = up
Use the altKey function(control structure) to check whether the [[Alt key]], Meta key, or Option key is being pressed. You can use altKey to add alternative capabilities to user actions such as clicking.
The altKey, optionKey, and metaKey functions all return the same value. Which one to use is a matter of preference. The terminology varies depending on platform. Users of different operating systems may know this key as the Option key (Mac OS systems), Meta key (Unix systems), or Alt key (Windows systems).