SR20 pilot on short final reported a critical ground conflict with another aircraft taking off.

Narrative

At about XA:30-XA:45PM; I entered ZZZ airspace; Class C; on a right downwind (via a 45) for Runway XX. I made several downwind calls; a base call; and a short final call with long landing kilo (the glide slope I was flying would put me about halfway down the runway). As I am about to pass the threshold and go over the numbers; a plane that was previously holding short on [Taxiway] 1 suddenly pulls out in front of me and calls 'IFR flight taking Runway XX;' I immediately pull my power and adjust my glide slope accordingly so I can hopefully land behind the now accelerating plane; and I ask them to expedite; as I had already called that I was on short final.Luckily; they managed to get in the air; and I landed behind them. I did not have to go around and pull hard to offset to the left or to the right. However; to do so; I had to slow to a dangerously low speed. If I had been a faster aircraft; or if the offending aircraft had been slower (and if I wasn't paying attention and adjusted accordingly); things might not have ended the same way.My suspicion is that they were receiving an IFR clearance; were not monitoring CTAF until the last minute; and/or did not visually check for traffic on final before departing; or perhaps they saw me and thought they could get out in time. In any case; it is a dangerous attitude in my opinion to not visually verify for traffic before taking a runway; even if it is Class C airspace.It is completely possible the pilot was not aware of me; and I understand just how busy IFR can be. I think it would be beneficial to contact the pilot and make him aware of this; so that any future near misses can be more likely to be avoided entirely.