The callback gets AnimationState* state which has a void* rendererObject field. You can use this to have context for the event. Eg, you could put your instance in rendererObject, then in the callback cast rendererObject to your instance and call a method on in.
A similar approach can be used when setting a callback for spTrackEntry. If the spTrackEntry owns the data, eg if you allocate a struct for the entry to store various pointers, then you need to set the disposeTrackEntry function for the spAnimationState, shown here.
Both approaches are used by spine-cocos2d-iphone and spine-cocos2dx:
https://github.com/EsotericSoftware/spi ... on.cpp#L43
spine-cocos2dx uses C++11 lambas to make spAnimaitonState event callbacks easier. The end result looks like this:
https://github.com/EsotericSoftware/spi ... le.cpp#L52
Note how the spTrackEntry callback is done on line 73.
Probably you'd want to build a small system for however you choose to do callbacks, then use that in your game.
