Recently I have posted this question:
I searched MSE and MO sites for related questions before asking, but didn't succeed, my bad. After few days, I encountered this old question, a little less specific than mine, but asking about same things:
The OP has been inactive for 4 years and hasn't accepted any answer. He's probably left the site forever.
Answers the question already had seemed somehow incomplete to me. But them helped me develop my own solution which, in my opinion, completely does for my question.
What should I do: answer my own question and mark the old one as duplicate or, conversely, answer (and edit) the old question and close the new?
UPDATE. I've posted answer to the new question and a comment to the old, as was suggested here. Other opinions and comments on subject are still welcome.