Canvas (or Control) Subclass empty Events ?

General
1

I do not understand the meaning of an empty event in a Subclass:

Event ObjectMoved(co As CanvasObject) Sub ()

Event ObjectSelected(co As CanvasObject) Sub ()

These comes from the example:
Examples>Graphics and Multimedia>ObjectsInCanvas>ObjectsInCanvas.xojo_binary_project

2

Look in the parent class.

BOTH the ParentClass and the SubClass might like to use the same event, for example the SuperClass does something that all sub controls should do, and the subclasses do something specific.

If the ParentClass uses the event ObjectMoved then the event ObjectMoved is not available in the subclass.

To make that event ALSO available in the subclass the ParentClass adds an EventDefinition and creates an event with the SAME name and parameters, in this case ObjectMoved. Now all the ParentClass has to do is call that new SubClass event in its own ObjectMoved event, otherwise the code in the subclass will never be called.

3

Thank you Markus for the explanation (the light in the dark).