Fires when the quest log updates.
This event is fired very often. This includes, but is not limited to:
- viewing a quest for the first time in a session in the Quest Log
- every time the player changes zones across an instance boundary
- every time the player picks up a non-grey item; every time after the player completes a quest goal, such as killing a mob for a ques
- It also fires whenever the player (or addon using the CollapseQuestHeader or ExpandQuestHeader functions) collapses or expands any zone header in the quest log.