elm_gesture_layer_cb_add/del functions have been added to provide this
functionality.
elm_gesture_layer_cb_set provided only one callback and so was
overriding the callback with the new one.
For ABI compatibility, some rules were needed:
- when set function is called with NULL, all the callbacks of the state will be
removed (old behavior respect)
- try to use set or add/del exclusively with a preference to the new
APIs. This is because of the first rule and because it will be more correct.
- if you remove a callback, only one instance of this callback of this
type/state for this gesture will be removed, by comparing func and data.
It means that if you register twice the same callback/data, it will be added
twice and you will have to remove also twice too.
Yakov Goldberg
Daniel Zaoui