I have one more question regarding translation of key (up/down) events.
How should I know when to send some key press as ascii value and when as K_* value?
For example when I call Ctrl::DoKeyFB with key 'a' as ascii code it is shown in Uword editor, but Ctrl+a won't work.
When I translate key 'a' to K_A, Ctrl+a works, but letter 'a' won't show in the editor.
Maybe I should call Ctrl::DoKeyFB twice? One call with ascii code and second one with K_* value?

In the SDL backend there are two separated paths SDL_TEXTINPUT and SDL_KEYDOWN/SDL_KEYUP in HandleSDLEvent.
But from libinput I receive just key up/down events