-- Supports lists, property lists, images, script instances and scalar values (integer, float, string, symbol).
on deepcopy (var, cycleCheck)
  case ilk(var) of
  #list, #propList, #image:
    return var.duplicate()
  #instance:
    if string(var) starts "<Xtra " then return var -- deep copy makes no sense for Xtra instances
    if voidP(cycleCheck) then cycleCheck = [:]
    if not voidP(cycleCheck[var]) then return cycleCheck[var]
    copy = var.script.rawNew()
    cycleCheck[var] = copy
    repeat with i = 1 to var.count
      copy.setProp(var.getPropAt(i), deepcopy(var[i], cycleCheck))
    end repeat
    return copy
  otherwise:
    return var
  end case
end