MainLoop

MainLoop is a term used to describe the central control flow that drives many interactive applications. It refers to the repetitive cycle that governs input processing, state updates, and output rendering. The loop is a core component in software ranging from desktop and mobile applications to games and certain embedded systems. It typically runs from program start until termination, continuously performing its cycle.

A common structure involves initialization, followed by a loop that repeats until a termination condition is met. Each cycle may include: processing input events or messages; updating the application state, physics, or AI; rendering a frame or producing output; and handling timing to regulate performance, such as calculating delta time or sleeping to cap the frame rate. The exact arrangement varies by domain. Game loops often employ fixed time steps for physics with rendering tied to the display rate. GUI event loops are frequently more event-driven, waking in response to user input, timers, or other events and rendering as needed.

Contexts and variants: in game engines, the MainLoop synchronizes simulation with rendering and often implements timing and interpolation strategies. In graphical user interfaces, the loop serves as the event dispatcher, ensuring responsiveness. In embedded systems, a “superloop” may cycle through tasks in a cooperative manner without a separate scheduler. In asynchronous programming, an event loop processes tasks from queues and handles non-blocking I/O.

Key considerations include responsiveness, determinism, latency, and frame pacing. Proper time management and, when applicable, safe concurrency are important for reliable and smooth operation.