First defined in: FKiSS4
The letheight action sets the value of variable to the
total height of object target, counting only cels which are mapped
and present in the current set (page).
variable
variable must be a variable name.
target
target may be an object number or a variable
representing an object number.
Example:
;@ letheight(H, #5) ; Set H to the overall height of all cels in object #5.
;@ letheight(H, VarObj) ; Set H to the overall height of all cels in the object identified by variable VarObj.