Fix link in README and some whitespace

README.md

@@ -1,10 +1,8 @@
 # gaemstone.ECS
 
-.. is a medium-level managed wrapper library around the [flecs-cs] bindings
-for the amazing [Entity Component System (ECS)][ECS] framework [Flecs]. It is
-used as part of the [gæmstone] game engine, but may be used in other projects
-as well. To efficiently use this library, a thorough understanding of [Flecs]
-is required.
+.. is a medium-level managed wrapper library around the [flecs-cs] bindings for the amazing [Entity Component System (ECS)][ECS] framework [Flecs]. It is used as part of the [gæmstone] game engine, but may be used in other projects as well. To efficiently use this library, a thorough understanding of [Flecs] is required.
+
+These classes have been split from the main [gæmstone] project. It is still a little unclear what functionality belongs where, and structural changes may occur. In its current state, I recommend to use this repository simply as a reference for building similar projects.
 
 [ECS]: https://en.wikipedia.org/wiki/Entity_component_system
 [Flecs]: https://github.com/SanderMertens/flecs
@@ -13,20 +11,18 @@ is required.
 
 ## Features
 
-These classes have only recently been split from the main **gæmstone** project. It is currently unclear what functionality belongs where, and structural changes are still very likely. In its current state, feel free to use **gæmstone.ECS** as a reference for building similar projects, or be aware that things are in flux, and in general nowhere near stable.
-
-- Simple wrapper structs such as [Entity] and [Identifier].
-- Classes with convenience functions like [EntityRef] and [EntityType].
+- Convenient wrapper types such as [Id], [Entity] and [EntityType].
 - [EntityPath] uses a unix-like path, for example `/Game/Players/copygirl`.
+- Fast type-to-entity lookup using generic context on [World]. (See below.)
 - Define your own [Components] as both value or reference types.
 - Query the ECS with [Iterators], [Filters], [Queries] and [Rules].
 - Create [Systems] for game logic and [Observers] to act on changes.
 
+[Id]:         ./src/gaemstone.ECS/Id.cs
 [Entity]:     ./src/gaemstone.ECS/Entity.cs
-[Identifier]: ./src/gaemstone.ECS/Identifier.cs
-[EntityRef]:  ./src/gaemstone.ECS/EntityRef.cs
 [EntityType]: ./src/gaemstone.ECS/EntityType.cs
 [EntityPath]: ./src/gaemstone.ECS/EntityPath.cs
+[World]:      ./src/gaemstone.ECS/World.cs
 [Components]: ./src/gaemstone.ECS/Component.cs
 [Iterators]:  ./src/gaemstone.ECS/Iterator.cs
 [Filters]:    ./src/gaemstone.ECS/Filter.cs
@@ -38,7 +34,7 @@ These classes have only recently been split from the main **gæmstone** project.
 ## Example
 
 ```cs
-var world = new World();
+var world = new World<Program>();
 
 var position = world
 	.New("Position")    // Create a new EntityBuilder, and set its name.
@@ -55,26 +51,31 @@ entities.NewChild("Two").Set(new Position(10, 20)).Build();
 
 // Changed my mind: Let's multiply each entity's position by 10.
 foreach (var child in entities.GetChildren()) {
-  ref var pos = ref child.GetRefOrThrow<Position>();
-  pos = new(pos.X * 10, pos.Y * 10);
+	ref var pos = ref child.GetRefOrThrow<Position>();
+	pos = new(pos.X * 10, pos.Y * 10);
 }
 
-var onUpdate = world.LookupByPathOrThrow("/flecs/pipeline/OnUpdate");
+// The following systems run in the "OnUpdate"
+// phase of the default pipeline provided by Flecs.
+var dependsOn = world.LookupPathOrThrow("/flecs/core/DependsOn");
+var onUpdate  = world.LookupPathOrThrow("/flecs/pipeline/OnUpdate");
 
 // Create a system that will move all entities with
 // the "Position" component downwards by 2 every frame.
-world.New("FallSystem").Build()
-	.InitSystem(onUpdate, new("Position"), iter => {
+world.New("FallSystem")
+	.Add(dependsOn, onUpdate)
+	.Build().InitSystem(new("Position"), iter => {
 		var posColumn = iter.Field<Position>(1);
 		for (var i = 0; i < iter.Count; i++) {
 			ref var pos = ref posColumn[i];
-			pos = new(pos.X, pos.Y + 2);
+			pos = new(pos.X, pos.Y - 2);
 		}
 	});
 
 // Create a system that will print out entities' positions.
 world.New("PrintPositionSystem").Build()
-	.InitSystem(onUpdate, new("[in] Position"), iter => {
+	.Add(dependsOn, onUpdate)
+	.InitSystem(new("[in] Position"), iter => {
 		var posColumn = iter.Field<Position>(1);
 		for (var i = 0; i < iter.Count; i++) {
 			var entity = iter.Entity(i);
@@ -109,3 +110,21 @@ dotnet add reference gaemstone.ECS/gaemstone.ECS.csproj
 # To generate flecs-cs' bindings:
 ./gaemstone.ECS/src/flecs-cs/library.sh
 ```
+
+## On the `TContext` type parameter
+
+Entities may be looked up simply by their type, once they're registered with `CreateLookup` or `InitComponent`. Under the hood, this is made possible using a nested static generic class that hold onto an `Entity` field. Theoretically this could be compiled into a simple field lookup and therefore be faster than dictionary lookups.
+
+To support scenarios where multiple worlds may be used simultaneously, each with their own unique type lookups, we specify a generic type as that context.
+
+In cases where only a single world is used, the amount of typing can be reduced by including a file similar to the following, defining global aliases:
+
+```cs
+global using Entity   = gaemstone.ECS.Entity<Context>;
+global using Id       = gaemstone.ECS.Id<Context>;
+global using Iterator = gaemstone.ECS.Iterator<Context>;
+global using World    = gaemstone.ECS.World<Context>;
+// Add more aliases as you feel they are needed.
+
+public struct Context {  }
+```

src/flecs-cs

@@ -1 +1 @@
-Subproject commit fcce5620d21fcd14c79d73a4406db8ce85f53dad
+Subproject commit 1ae8ffade56a279d450dbf42545afbf873bdbafe

src/gaemstone.ECS/Entity.cs

@@ -21,7 +21,7 @@ public unsafe readonly partial struct Entity<TContext>
 	public bool IsValid => EntityAccess.IsValid(World, this);
 	public bool IsAlive => IsSome && EntityAccess.IsAlive(World, this);
 
-	public string? Name	  { get => EntityAccess.GetName(World, this);   set => EntityAccess.SetName(World, this, value); }
+	public string? Name   { get => EntityAccess.GetName(World, this);   set => EntityAccess.SetName(World, this, value); }
 	public string? Symbol { get => EntityAccess.GetSymbol(World, this); set => EntityAccess.SetSymbol(World, this, value); }
 
 	public EntityPath Path => EntityPath.From(World, this);
@@ -30,7 +30,7 @@ public unsafe readonly partial struct Entity<TContext>
 	public Entity<TContext>? Parent
 		=> GetOrNull(World, GetTargets(FlecsBuiltIn.ChildOf).FirstOrDefault());
 	public IEnumerable<Entity<TContext>> Children
-		=> Iterator<TContext>.FromTerm(World, new(FlecsBuiltIn.ChildOf, this)).GetAllEntities();
+		=> World.Term(new(FlecsBuiltIn.ChildOf, this)).GetAllEntities();
 
 
 	private Entity(World<TContext> world, Entity value)
@@ -76,7 +76,8 @@ public unsafe readonly partial struct Entity<TContext>
 	public Entity<TContext> ChildOf(Entity parent)
 		=> Add(FlecsBuiltIn.ChildOf, parent);
 
-	public bool IsDisabled => Has(FlecsBuiltIn.Disabled);
+	public bool IsDisabled =>  Has(FlecsBuiltIn.Disabled);
+	public bool IsEnabled  => !Has(FlecsBuiltIn.Disabled);
 	public Entity<TContext> Disable() => Add(FlecsBuiltIn.Disabled);
 	public Entity<TContext> Enable()  => Remove(FlecsBuiltIn.Disabled);
 

src/gaemstone.ECS/EntityBuilder.cs

@@ -109,11 +109,11 @@ public class EntityBuilder<TContext>
 		using var alloc = TempAllocator.Use();
 		var desc = new ecs_entity_desc_t {
 			id         = Id,
-			name       = (Path != null) ? alloc.AllocateCString(Path.Name.AsSpan()) : default,
-			symbol     = alloc.AllocateCString(_symbol),
-			add_expr   = alloc.AllocateCString(Expression),
+			_name      = (Path != null) ? alloc.AllocateCString(Path.Name.AsSpan()) : default,
+			_symbol    = alloc.AllocateCString(_symbol),
+			_add_expr  = alloc.AllocateCString(Expression),
 			use_low_id = UseLowId,
-			sep        = CStringExtensions.ETX,
+			_sep       = CStringExtensions.Empty,
 		};
 
 		var add = desc.add; var index = 0;

src/gaemstone.ECS/EntityPath.cs

@@ -197,7 +197,7 @@ public class EntityPath
 		foreach (var part in path)
 			fixed (byte* ptr = part.AsSpan())
 				if (skipLookup || (parent = new(ecs_lookup_child(world, parent, ptr))).IsNone) {
-					var desc = new ecs_entity_desc_t { name = ptr, sep = CStringExtensions.ETX };
+					var desc = new ecs_entity_desc_t { _name = ptr, _sep = CStringExtensions.Empty };
 					if (parent.IsSome) desc.add[0] = Id.Pair(FlecsBuiltIn.ChildOf, parent);
 					parent = new(ecs_entity_init(world, &desc));
 					skipLookup = true;

src/gaemstone.ECS/Filter.cs

@@ -77,7 +77,7 @@ public class FilterDesc
 	public unsafe ecs_filter_desc_t ToFlecs(IAllocator allocator)
 	{
 		var desc = new ecs_filter_desc_t {
-			expr      = allocator.AllocateCString(Expression),
+			_expr     = allocator.AllocateCString(Expression),
 			instanced = Instanced,
 			entity    = Entity,
 		};

src/gaemstone.ECS/Internal/Iterator.cs

@@ -58,6 +58,9 @@ public unsafe class Iterator
 	public Entity First()
 		=> new(ecs_iter_first(Handle));
 
+	public bool Any()
+		=> ecs_iter_is_true(Handle);
+
 	public IEnumerable<Entity> GetAllEntities()
 	{
 		while (Next())

src/gaemstone.ECS/Iterator.cs

@@ -29,6 +29,8 @@ public unsafe class Iterator<TContext> : Iterator
 	public new Iterator<TContext> SetVar(Variable var, Entity entity)
 		=> (Iterator<TContext>)base.SetVar(var, entity);
 
+	public new Entity<TContext>? First()
+		=> Entity<TContext>.GetOrNull(World, base.First());
 	public new IEnumerable<Entity<TContext>> GetAllEntities()
 		=> base.GetAllEntities().Select(e => Entity<TContext>.GetOrInvalid(World, e));
 

src/gaemstone.ECS/Rule.cs

@@ -52,9 +52,9 @@ public unsafe class Rule<TContext>
 
 		internal VariableCollection(ecs_rule_t* handle)
 		{
-			// Find the $This variable, if the rule has one.
+			// Find the $this variable, if the rule has one.
 			var thisIndex = ecs_filter_find_this_var(ecs_rule_get_filter(handle));
-			if (thisIndex >= 0) _variables.Add(new(thisIndex, "This"));
+			if (thisIndex >= 0) _variables.Add(new(thisIndex, "this"));
 
 			// Find all the other "accessible" variables.
 			var count = ecs_rule_var_count(handle);

src/gaemstone.ECS/Term.cs

@@ -61,7 +61,7 @@ public enum TermOperKind
 
 public class TermId
 {
-	public static TermId This { get; } = new("$This");
+	public static TermId This { get; } = new("$this");
 
 	public Entity Id { get; }
 	public string? Name { get; }
@@ -80,7 +80,7 @@ public class TermId
 
 	public ecs_term_id_t ToFlecs(IAllocator allocator) => new() {
 		id    = Id,
-		name  = allocator.AllocateCString(Name),
+		_name = allocator.AllocateCString(Name),
 		trav  = Traverse,
 		flags = (ecs_flags32_t)(uint)Flags
 	};

src/gaemstone.ECS/Utility/CStringExtensions.cs

@@ -8,7 +8,6 @@ namespace gaemstone.ECS.Utility;
 public unsafe static class CStringExtensions
 {
 	public static CString Empty { get; } = (CString)"";
-	public static CString ETX { get; } = (CString)"\x3"; // TODO: Temporary, until flecs supports Empty.
 
 	public static unsafe byte[]? FlecsToBytes(this CString str)
 	{

src/gaemstone.ECS/World+Bare.cs

@@ -17,7 +17,9 @@ public unsafe struct World
 	public World(ecs_world_t* handle)
 		=> Handle = handle;
 
-	public World(params string[] args)
+	/// <summary> Initializes a new Flecs world. </summary>
+	/// <param name="minimal"> If true, doesn't automatically import built-in modules. </param>
+	public World(bool minimal = false)
 	{
 		[UnmanagedCallersOnly]
 		static void Abort() => throw new FlecsAbortException();
@@ -27,7 +29,7 @@ public unsafe struct World
 		api.abort_ = new FnPtr_Void { Pointer = &Abort };
 		ecs_os_set_api(&api);
 
-		Handle = ecs_init_w_args(args.Length, null);
+		Handle = minimal ? ecs_mini() : ecs_init();
 	}
 
 	public bool Progress(TimeSpan delta)

src/gaemstone.ECS/World.cs

@@ -15,8 +15,11 @@ public unsafe struct World<TContext>
 
 	public World(World value)
 		=> Value = value;
-	public World(params string[] args)
-		: this(new World(args)) {  }
+
+	/// <summary> Initializes a new Flecs world. </summary>
+	/// <param name="minimal"> If true, doesn't automatically import built-in modules. </param>
+	public World(bool minimal = false)
+		: this(new World(minimal)) {  }
 
 	public bool Progress(TimeSpan delta) => Value.Progress(delta);
 	public void Quit()    => Value.Quit();
@@ -57,6 +60,12 @@ public unsafe struct World<TContext>
 		=> Pair(Entity<TRelation>(), Entity<TTarget>());
 
 
+	public Iterator<TContext> Term(Term term) => Iterator<TContext>.FromTerm(this, term);
+	public Filter<TContext> Filter(FilterDesc desc) => new(this, desc);
+	public Query<TContext> Query(QueryDesc desc) => new(this, desc);
+	public Rule<TContext> Rule(FilterDesc desc) => new(this, desc);
+
+
 	public bool Equals(World<TContext> other) => Value == other.Value;
 	public override bool Equals(object? obj) => (obj is World<TContext> other) && Equals(other);
 	public override int GetHashCode() => Value.GetHashCode();