GtkIMContext needs to forward key events without key codes
Seems gtk_im_context_filter_key() calculate keyval from keycode. But most IME sends keyval only and don't know how to calculate keycode. Creating GdkEventKey with keycode = 0 has worked in Xorg.
Could you provide the argument of keyval in gtk_im_context_filter_key() and calculate keycode from keyval if keycode is zero?
ibus-hangul:
https://github.com/libhangul/ibus-hangul/blob/master/src/engine.c#L1582
ibus-bogo:
https://github.com/BoGoEngine/ibus-bogo/blob/master/ibus_engine/surrounding_text_backend.py#L129