Thanks a lot for your answer.
In the real application there will be no pushbuttons I described. All input events will be delivered by UART (through qextserialport lib). So basically I want to implement a sort of mouseless device driven by external buttons and it looks like those fake key events are all I need.

My thoughts were like that: If I can control my application run on my PC without mouse - why don't implement the same behavior in the embedded device by fake keys.

Maybe my real problem now is those buttons (which are supposed to be on the external device) I click by my mouse. So when I click one of them something happens with focus (my target widget looses it for a moment for example).

Anyway I'll try to send some events through UART to the my application and fire the same fake key events. I hope it will work.