User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:41.0) Gecko/20100101 Firefox/41.0 Build ID: 20150628030215 Steps to reproduce: 1. A device with both built-in qwerty and built-in 12keys 2. A device with HID keyboard feature. 3. A device with HID keyboard feature and a built-in hardware keyboard. 4. OEM Keyboard app downloaded from marketplace, it's possible because IME API has a privileged permission. In those cases, how can keyboard app select a proper IME state machine exactly for the keyboard events without knowledge of the currently installed hardware keyboards? Actual results: Keyboard apps might have the IME state machines for the various hardware keyboard types, because it's needed to handle a keyboard event from each hardware keyboard in a different way. However, keyboard apps can not select a proper IME state machine for each keyboard event because keyboard apps do not have any knowledge of the currently installed hardware keyboards. Expected results: Keyboard app should be able to select a proper IME state machine for each keyboard event using the knowledge of the currently installed hardware keyboards.

As we discussed in Bug 1161424, in my opinion, the knowledge of the types of hardware keyboards is needed in keyboard app. Summary for new requirement ============================= 1. Info of which hardware keyboard a keyboard event is fired from? => Once keyboard app receives a hardware keyboard event, it can select a proper IME state machine using this info. 2. Info of which hardware keyboard is installed to device. => Keyboard app can prepare UI or state machine on initialization using this info. 3. Notification to keyboard app, which contains hardware keyboard is attached or detached newly. => Once keyboard app receives this event, it calls hardwareinput.addEventListener or hardwareinput.removeEventListener for the updated hardware keyboard. About 2, I'm not sure it's needed or not. If I have misunderstandings, let me know please. And if those are really needed, give me your opinion please.

Is there any usecase that we may use a qwerty hardware keyboard from HID and a built-in 12 keys hardware keyboard at the same time? If not, then we can just set the proper IME by the hardware keyboard used.