Struggles with callbacks between c++ objects

In my plan to have an object for the open effects box as a whole, including the firmware and the overall structure of the user interface, and another to wrap the physical object including the pin assignments, switch handling, etc., I wanted to have the hardware wrapper able to call back to the overall object when a switch changes state or is held to auto-repeat. The callback cannot be a static function, as it needs to modify member variables.

While it is apparently possible for an object to set a callback to one of its own methods, that callback has to include some way to refer to the object itself, so that the object structure and variables are available. However, that requires the hardware wrapper’s setCallback method to know about the calling class. Thus the hardware wrapper class has to include the calling class’ header file; but the calling class has to include the hardware wrapper class’ header file, since it’s instantiating that class for part of its functionality.

Seems like an infinite loop of inclusion; this can be protected in the usual way, but I haven’t been able to make it work.

Thus I’m going to abandon this line of attack and send a bunch of pointers to the hardware wrapper so it can set flags “thisThingyHasChangedState” for the calling class to poll. Ugh.