v3_draft.c

// Draft for low-level macro-less API
// 
// The goal of this draft is to explore a full-featured minimal API that does not rely on macro's. That should make it easier to port 
// flecs to other languages, and allow for more straightforward integration with other frameworks / engines. This is not meant as a
// full replacement for an application-facing API, though should be able to coexist with one.
//
// Inspiration for naming conventions & declarative design comes from Sokol Gfx

// Create world as usual
ecs_world_t *world = ecs_init();

// Set world parameters
ecs_update_world(world, &(ecs_world_desc){
  .target_fps = 60,
  .thread_count = 4,
  .trace_level = 3
});

// Register component
ecs_entity_t ecs_typeid(Position) = ecs_make_entity(world, &(ecs_entity_desc){
  .name = "Position",
  .components = {ecs_typeid(EcsComponent)},
  .values = {
    &(EcsComponent){sizeof(Position), alignof(Position)}
  }
});

// Register tag, which is equivalent to an empty entity
ecs_entity_t Dirty = ecs_make_entity(world, &(ecs_entity_desc){
  .name = "Dirty"
});

// Create a prefab entity, by adding the Prefab tag
ecs_entity_t base = ecs_make_entity(world, &(ecs_entity_desc){
  .name = "myPrefab",
  .components = {EcsPrefab, ecs_typeid(Mass)},
  .values = {
    NULL,
    &(Mass){10}
  }
});

// Create regular entity & initialize components
ecs_entity_t e1 = ecs_make_entity(world, &(ecs_entity_desc){
  .name = "e1",
  .components = {ecs_typeid(Position), ecs_typeid(Velocity), ECS_INSTANCEOF | base}
  .values = {
    &(Position){10, 20},
    &(Velocity){1, 2},
  }
});

// Add & set component
ecs_update_entity(world, e1, &(ecs_entity_desc){
  .add = {ecs_typeid(Mass), Dirty},
  .values = {
    &(Mass){10}
  }
});

// Create system, which is a query + a callback
ecs_make_query(world, &(ecs_query_desc){
  .name = "Move",
  .callback = Move,
  .components = {EcsOnUpdate},
  .signature = {
    {EcsInOut, ecs_typeid(Position)},
    {EcsIn,    ecs_typeid(Velocity)}
  }
});