Use keycode for Print Screen(`KC_PSCREEN` or `KC_PSCR`) instead of `KC_SYSREQ`. Key combination of 'Alt + Print Screen' is recognized as 'System request'.
Solves my personal 'the' problem. I often got 'the' or 'THe' wrongly instead of 'The'. Oneshot Shift mitgates this for me.
https://github.com/tmk/tmk_keyboard/issues/67
## Modifier/Layer stuck
Modifier keys or layers can be stuck unless layer switching is configured properly.
For Modifier keys and layer actions you have to place `KC_TRANS` on same position of destination layer to unregister the modifier key or return to previous layer on release event.
This feature is for *mechanical lock switch* like this Alps one.
http://deskthority.net/wiki/Alps_SKCL_Lock
Using enabling this feature and using keycodes `LCAP`, `LNUM` or `LSCR` in keymap you can use physical locking CapsLock, NumLock or ScrollLock keys as you expected.
Old vintage mechanical keyboards occasionally have lock switches but modern ones don't have. ***You don't need this feature in most case and just use keycodes `CAPS`, `NLCK` and `SLCK`.***
Apple keyboard sends keycode for Fn unlike most of other keyboards.
I think you can send Apple Fn key using Apple venter specific Page 0xff00 and usage 0x0003. But you have to change HID Report Descriptor for this, of course.
Japanese JIS keyboard specific keys like `無変換(Muhenkan)`, `変換(Henkan)`, `ひらがな(hiragana)` are not recognized on OSX. You can use **Seil** to enable those keys, try following options.
Karabiner - Keymapping tool on Mac OSX - ignores inputs from RN-42 module by default. You have to enable this option to make Karabiner working with your keyboard.