The IUP GUI

The latter GUI that I added to the engine was IUP. It was natural to choose it because its authors are the same of the Lua language, so it was very easy to embed it in the engine.
You may ask why I needed another GUI, when I was already so satisfied by GLGooey. The answer is simple: while GLGooey lives in the OpenGL window, IUP is a native GUI that acts outside the game window. It is very useful when a programmer needs to manage the objects rendered in the scene with a complete set of components at hand. For example, one can create an editor to control the world, like in the simplified example of the “NativeGui” demo included in DemoPack3 (see the screenshot).
In conclusion, APOCALYX users can program in Lua three different GUIs: one very easy to use and useful in the desing phase of the game (TweakBar), another to create in-game interfaces (GLGooey) and, finally, one (IUP) to build very complex tools, such as editors around the rendered world. This way, I think that almost all the possible needs are covered.