|closest player to sprite
|sprite being damaged
EVENT_PREACTORDAMAGE is a Game Event.
RETURN is initially set to 0. If nonzero, damage will not be applied for this run of the damage calculation -- however, htextra will also not be set to -1, meaning that without doing anything else, the next execution of ifhitweapon may still apply the damage.
Altering htextra in this state allows you to change the accumulated damage that is applied to the actor's health.