Actually, the trigger mechanism in European firearms evolved from something that beared no Resemblance from the crossbow trigger mechanism in Chinese crossbows. The original European trigger was simply a lever that held a piece of burning rope. Pulling on the lever puts the burning end of the rope against the touchhole on the barrel. That's called match lock. Later it evolved into clockwork mechanism that spun a wheel that struck a spark to light the powder in the barrel. That's called a wheel lock. Only finally did it evolve independently into something that very vaguely resembled Chinese crossbow trigger. That's flint lock.