I tested textinput with windowns phone 8 xaml. I press key enter on virtual keypad to close IME, it working fine. but if touch outside or press keyback of device to close IME, it have been missed event detach and it will return event detach when IME show on next time
I have not tested for other devices.
this is log of textinput into testcpp
TEXTFIELD_EVENT_ATTACH_WITH_IME TEXTFIELD_EVENT_ATTACH_WITH_IME TEXTFIELD_EVENT_DETACH_WITH_IME