Target markers placed automatically
 

I was doing some mythics earlier and it seems there is an addon, Weak Auras and something else, which would place a Moon over a particular target out of a pack of enemies (in this case the one with highest HP because of the Bolster affix).

I was trying to imagine how it might work.

I can only guess that when you go in combat, there will be events about enemies aggroing you or your party members ? And then the addon must be using some API to place a target marker over a specific target ? And even if there are multiple targets with the same name, eg "Crazed Disciple", I guess it still somehow works and can tell who is who and mark the right one ?

I mean DBM puts markets on players, so I presume an addon can place a marker over an enemy ? The clever bit is that the marker is placed on the pull before you even have the chance to hit anything or to be hit, so it works not off of your attacks, but on some kind of aggro message/event.

Am I right in all these assertions?

It's polling the combat log for events from enemies. Once it sees an enemy is engaged, it logs its unique guid and the health of that GUID. It then likely compares the players target, focus, or mouseover to that table constantly so that it can setraidtarget on any of those units if their health is lowest. This weak aura or add-on likely will not update correctly if the player doesn't mouseover or change targets enemies or their nameplates.

Addons can read nameplate units directly if nameplates are enabled. Bosses can also be read in fights that have boss UnitFrames, which are typically in raids.

Thanks for the replies, guys.