Event of SAP controls

Dear All expert,

I am confused with event register function. For example , for example event 'Hotspot' only need code

'Set handler....' to register, then it will be triggerred.But for event 'data changed' , It is need call method 'REGISTER_EDIT_EVENT'.

addtional to registerred.

Is there any regulaion for the event register ? Or only case by case ?

Thanks for your reply in advance !