TL;DR
Stop wasting CPU time and making noise when nobody is watching.What ?
When factorio is minimized in the main menu then all background simulations should stop. When in a single player game the game should be put on pause, just like when opening research. For multiplayer games it should just go mute as leaving and joining the game would be too inconvenient and pausing would affect all players, if the player even has the right for it.Why ?
There is no point in running those mini simulations for the wallpaper if there is nothing there to display them on and nobody is watching. There is no simple way to pause factorio while in main menu. It always consumes cpu time and always makes noise. The game could run the current simulation till completion and simply not start another while minimized.For games it would be a convenience to have the game pause and go silent when minimized. Together with the option to minimize the game when loosing focus this would make alt-tab a "boss key". It would be possible to just accept an incoming voice or video call and the game would go quite automatically. As is any interruption of game time requires more actions.