Labels:text | font | screenshot | handwriting OCR: Note Callback names are shared by a class, i.e. referenced by the class's action methods. But callback name/function pairs are instance data and are recorded in a contact's callbacks slot. In our example, every blinker is expected to have a :blink call- back function, but each blinker usually has a different :blink callback function. That is, each blinker usually has different application semantics.
