LabVIEW
animaiton of 2D graph
By the way, here's an expansion on that guess, using an analogy from LVOOP, which might make it easier to understand:
I've posted an idea here for allowing property node support in LVOOP:
As you can see from the mock-up on the left, this is accomplished by a special kind of VI, which is guaranteed to have a single input. I'm assuming NI uses an equivalent mechanism for the properties - something which allows you to generate a member function which will write the value into one of the class data members.
There is another option, although that seems less likely - in C++, you can define a data member of a class as public. The parallel in LabVIEW would be to extend my idea - allow us to mark some of the elements in the cluster as public, which would expose them in the property node without us having to write any code. The reason I didn't suggest this and why I'm guessing NI didn't do this in the C++ code is that this is generally considered bad form - if you allow outside users to directly manipulate data in your class you have two problems - first, they can give you bad data and second, this prevents you from being able to modify your class later on.
