1.2

Bug fixes

• Fixed 1lu being interpreted as 32-bit on MSVC and breaking buckets
• Fixed unwanted min and max defines on MSVC
• Allow lambda functions as event listeners

1.1

General

• Various performance improvements through a new custom data structure utilizing hierarchical bitmasks and low complexity jump-counting
• The "registry" is renamed from ecs to scene, better reflecting how it ought to be used
• Added unit tests and synthetic benchmark

Events & systems

• Systems are no longer contained in the scene; create them separately and connect them to the scene with scene::add_receiver()
  • Removed scene::add_system(), scene::ensure_system(), scene::clear_systems(), class dependency_systems
  • Added scene::add_receiver() for making the scene route requested event types to the receiver (= a system)
  • Added scene::get_handler_count() for getting the number of parties receiving events of the given type
  • Added scene::add_event_handler() for adding a callback function for events
  • Added scene::bind_event_handler() for adding member function callbacks for events
  • Added scene::remove_event_handler() for removing event callbacks
  • Added scene::subscribe() and class event_subscription for automatic RAII handling of event handler addition and removal
• emitter has been removed; you can now emit with scene::emit() without having to declare emittable types ahead of time

Search index

• New feature! Allows for quick searching of entities based on the values of their components (e.g. find an entity by its name component in constant time)
• Added class search_index that can be specialized to implement a search index for your component type
• Added scene::find_component() to find components with the search index
• Added scene::find() to find entities with the search index
• Added scene::update_search_index() to force a search index refresh (needed if a component's indexed content changes after creation)
• Added scene::update_search_indices() to force a search index refresh for all known component types

Components & entities

• Pointer stability is now always guaranteed for every component type (ptr_component has been removed)
• scene::reserve() has been removed
• scene::emplace() has been added for creating a component in-place
• scene::concat() has been added for copying all entities from one scene to another
• scene::copy() has been added for copying one entity from one scene to another

Initial release

It should be ready to use in its current state, but no guarantees. The code is originally from a couple years old game engine codebase which is somewhat tested.