Any idea what a game loop would look like for an ECS engine that only renders a new frame when some animation is running or when the user is manipulating the camera, but not otherwise?
Let's not argue "why". Most obvious would be saving battery.
The bevy engine (ECS based) has an `UpdateMode` that specifies "Continuous" vs "Reactive" https://docs.rs/bevy/0.10.1/bevy/winit/enum.UpdateMode.html.
Here's an example using it, it's well suited for "desktop applications", the shorthand to use it is `desktop_app()` https://github.com/bevyengine/bevy/blob/1c5c94715cb17cda5ae2....