Project – CosmosUI

CosmosUI is an open source interface modification of World of Warcraft. Many of the CosmosUI additions were later implemented by Blizzard on the default interface.

I had been doing Warcraft III map making for more than a year when World of Warcraft has been leaked. This was really exciting to hack into the game and being able to modify it. Since I had no real programming knowledge at the time, I could not help people making a server for the game. However, I found the interface in XML and Lua really interesting and spent some time tweaking it.

There was nothing real to do in the sandbox servers at the time, I spent some time programming MiniGames (TicTacToe, Connect 4) in the interface. I have been remarked by Thott ( that gave me a Beta key in order to work on the open source interface modification project he took part: CosmosUI.

I have been working on CosmosUI during the whole beta and these are my notable additions.


During the Beta of World of Warcraft, the only way to see your quest progression was to open the quest log and search for the quest you were doing. I made an addon that would show a summary of the quest you wanted in a small movable box located under the minimap by default.

Since I did not want to maintain a standalone version people started making addons with this concept. The most successful is MonkeyQuest downloaded 1 million times. Blizzard added later a Quest Tracker functionality to the World of Warcraft default interface that is a nearly exact copy of QuestMinion. The game Warhammer Online made the same choice for its interface.

Quest Minion

Quest Minion

World of Warcraft

World of Warcraft

Warhammer Online

Warhammer Online


At the beginning, CosmosUI was just modifications of the World of Warcraft interface files. This was good for small modifications but once CosmosUI grew, we had to make some tricky diff every time a World of Warcraft patch was released. CosmosUI was the only interface modification at the time, so people would be without interface for about 12-24 hours while we were merging everything.

I found a solution to this problem. Instead of modifying the actual code, we can hook the specified function and put our custom code in another file of our own.

local thefunction_backup = thefunction
thefunction = function (args)
  -- Do what we want before
  -- Do what we want after

I first moved my modifications out of the Blizzard code and everyone started to do so. Then a few weeks later Blizzard implemented an addon manager into the game. With the preliminary work we did, it was really easy to transform CosmosUI into an addon without any file dependency.


When I started working on CosmosUI, it was only available in English. Since I am French, I wanted my fellows to be able to use it in their native language.

CosmosUI being a compilation of multiple addons, I first started to make a translation template and applied it to my own addons. Then I put all the strings of all the CosmosUI addons into their respective English translation file. And finally, I formed a translation team composed of French and German people.

Once everything was translated, I started to advertise CosmosUI in the French community and made the technical support.

Sky - Communication Library

In order to make my MiniGames multiplayer, i had to transfert data between the two players. The only way at the time to achieve it was by text messages. However, they are visible to the user. My work on Sky was to automatically join a channel, hide all messages from this channel, make it invisible to the user and finally intercept the incoming messages.

Since channels were only available with command lines, they weren't used that much and their internal API was really buggy. Most of the job was to find workarounds for these bugs. Sometimes channels weren't saved across sessions, they would be joined there but not listed or not joinable at all. For more information you can read the description on WoWWiki


Christopher was one of our top contributors on the Cosmos project, overseeing both community relationships in the French community as well as developing several mods within the community. The most revolutionary of these was the Quest Helper addon, which became so infamous and popular that Blizzard added it into their base UI. Christopher was a major contributor to the project's culture, content and community. It would not have been the success it was without his direct contribution and passionate commitment.” April 27, 2009 -- Alexander Brazie, Cosmos UI Team Leader. (LinkedIn)

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