Events/Q

This event fires when an escort quest is started by another player. A dialog appears asking if the player also wants to start the quest.

arg1 

Name of player who is starting escort quest.

arg2 

Title of escort quest. Eg. "Protecting the Shipment"

Fired after the player hits the "Continue" button in the quest-information page, before the "Complete Quest" button.

In other words it fires when you are given the option to complete a quest, but just before you actually complete the quest (as stated above).

Fired when the player is given a more detailed view of his quest.

Fired whenever the quest frame changes (Detail to Progress to Reward, etc.) or is closed.

arg1 

mousebutton (LeftButton)

Fired when talking to an NPC that offers or accepts more than one quest, i.e. has more than one active or available quest.

Fired when the quest items are updated

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; (once for each quest?) 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 quest. It also fires whenever the player (or addon using the CollapseQuestHeader or ExpandQuestHeader() functions) collapses or expands any zone header in the quest log.

Fired when a player is talking to an NPC about the status of a quest and has not yet clicked the complete button.

Fired just before a quest goal was completed. At this point the game client's quest data is not yet updated, but will be after a subsequent QUEST_LOG_UPDATE event.

arg1 

questIndex (not watch index)