Waits until {condition} evaluates to TRUE, where {condition} is a Funcref or string containing an expression.

{timeout} is the maximum waiting time in milliseconds, -1 means forever.

Condition is evaluated on user events, internal events, and every {interval} milliseconds (default: 200).

Returns a status integer: 0 if the condition was satisfied before timeout -1 if the timeout was exceeded -2 if the function was interrupted (by CTRL-C) -3 if an error occurred