[TazeTSchnitzel]

I think 1, 2 and maybe 3 could all be done with a traditional retained mode GUI, and indeed there are retained mode GUI systems for games. The big traditional UI frameworks just have not been made to work well with games. Which is fair, game engines are alien environments that may as well be considered their own platforms.

> It's worth pointing out that the immediate/retained split doesn't apply only to the GUI

Indeed. Modern game engines, and in particular almost all 3D games, use what could be described as a “retained mode” system for the rendering of the game itself — the scene graph — so it is interesting that the UI doesn't always match that.

[seanmcdirmid]

Generic retained mode is dead, but creating a scene graph driven by something other than imperative updates (eg constraint satisfaction via a physics engine) is alive and well. The problem is that you can’t overlay the former very well in the latter, so things like OGL retained mode are never used anymore.