I am looking for any open source implementations that allow for a creation of rendered objects like World of Warcrafts addon system. I am interested in recreating something similar in my own projects that make use of Direct3D8 and Direct3D9 but have not seen any similar projects to what WoW's addon system can handle.
I have a home-brewed method that can do partially what WoW does but nothing anywhere close to as advanced as their system(s).
Attempting to Google anything WoW related with programming gives nothing useful but addon websites for the game itself and nothing towards open source things for use in other projects.
The current method I am doing is by using primitive objects rendered via vertices and allowing sprites to override the primitive and be rendered instead. As-is, I can create UI elements like this:
This is made up of 6 different 'objects' that parent to one another. Another example would be:
This one is made up of 3 objects, with two being overridden with a sprite.
I'm interested in seeing similar projects to compare and learn from to extend my system or start a new one from the ground up with better implementation ideas in mind.