One feature that's to be introduced in World of Warcraft's game patch 2.4 is a heavily improved combat log. While this change isn't going to be as visible as some of the new tweaks, its effects on your gaming will be considerable. For one, as Vaneras explained, WoW's improved Combat log will feature easier AddOn maintenance.

Another new innovation that Vaneras discussed is the combat log's filters:

The combat log stores the last five minutes worth of raw combat events. Filters can be setup on multiple criteria, affiliation, ownership, etc. Any events that match the current filter are passed through the client via the COMBAT_LOG_EVENT message. The combat log filter is global. However, AddOns which want to parse all events the moment they happen can register for the COMBAT_LOG_EVENT_UNFILTERED message. This should allow all existing AddOns to still respond to combat events without a complicated middle-manager AddOn.


Another new feature you'll notice is that the log will come in two text formats. The first is the standard text you're familiar with. The new text in question is in terse format, which contains the source, target, spell, action and result. Vaneras explained that this format will make for easier to write to AddOns which are going to be re-written for patch 2.4 compatibility.

That's just a quick glance of some of the new features being discussed regarding WoW's new combat log. You can view Vaneras' full guide over in the source link.