execute-with-interface-if-alive applies the function
to the arguments
in the process of the interface
, if the interface is "alive". An interface become alive during the creation process before interface-display is called (and before display returns). It stops being alive once it is destroyed, either programmatically or by the user.
If interface is not alive, function is not applied. This is in contrast to execute-with-interface, which in this case applies the function in the current process.
execute-with-interface-if-alive on the dead interface. It should be checked only when the caller knows that the interface is already displayed (display returned, or interface-display was called on it), otherwise it may be
nil because it is not displayed yet.
execute-with-interface-if-alive is one way of ensuring this.
CAPI User Guide and Reference Manual (Macintosh version) - 25 Feb 2015