January 19th 2020
Notifies the core that the input currently being handled by a view context thread should be treated as if it were not handled
the standard custom layer context pointer
When events are handled, future handlers for them are skipped. This is especially important because text input is passed as a seperate event after key stroke events, and if a key stroke event is marked as handled, then the text event that would have been generated by the key stroke is skipped.