flecs: A C repository from AlexMog

Flecs is a fast and lightweight Entity Component System for C89 / C99 / C++11 that packs a lot of punch in a small footprint:

Blazing fast iteration speeds with direct access to raw C arrays across multiple components
Support for hierarchies, prefabs, traits, state machines, snapshots and more
An efficient lock-free architecture allows for modifying entities across multiple threads
Queries with builtin support for sorting, change tracking, read-write permissions and more
Systems that are time triggered, rate triggered, run every frame or run only when needed
A customizable core that lets you include only the features you need

This is Flecs v2, which is a breaking change from v1. For the last v1 release, see: https://github.com/SanderMertens/flecs/releases/tag/v1.3

If you have questions, suggestions or a Flecs project you'd like to show off, join the Flecs Discord!

What is an Entity Component System?

ECS (Entity Component System) is a design pattern often found in gaming and simulation which produces code that is fast and reusable. Dynamic omposition is a first-class citizen in ECS, and there is a strict separation between data and behavior. A framework is an Entity Component System if it:

Has entities that are unique identifiers
Has components that are plain data types
Has systems which are behavior matched with entities based on their components

Documentation

See Docsforge for a more readable version of the documentation.

Example

This is a simple flecs example in the C++11 API:

struct Position {
    float x;
    float y;
};

struct Velocity {
    float x;
    float y;
};

int main(int argc, char *argv[]) {
    flecs::world ecs;

    ecs.system<Position, const Velocity>()
        .each([](flecs::entity e, Position& p, const Velocity& v) {
            p.x += v.x * e.delta_time();
            p.y += v.y * e.delta_time();
            std::cout << "Entity " << e.name() << " moved!" << std::endl;
        });

    ecs.entity("MyEntity")
        .set<Position>({0, 0})
        .set<Velocity>({1, 1});

    while (ecs.progress()) { }
}

Building

The easiest way to add Flecs to a project is to add flecs.c and flecs.h to your source code. These files can be added to both C and C++ projects (the C++ API is embedded in flecs.h). Alternatively you can also build Flecs as a library by using the cmake, meson, bazel or bake buildfiles.

Custom builds

The Flecs source has a modular design which makes it easy to strip out code you don't need. At its core, Flecs is a minimalistic ECS library with a lot of optional features that you can choose to include or not. This section of the manual describes how to customize which features to include.

Modules

The following modules are available in flecs-hub and are compatible with v2: