Add ecs.scene

ecs/ecs.can

@@ -1,5 +1,7 @@
 --- ubiquitousse.ecs
--- No dependency.
+-- Optional dependency: ubiquitousse.scene, to allow quick creation of ECS-based scenes.
+local loaded, newScene = pcall(require, (...):match("^(.-)ecs").."scene")
+if not loaded then newScene = nil end
 
 --- Entity Component System library, inspired by the excellent tiny-ecs. Main differences include:
 -- * ability to nest systems;
@@ -109,9 +111,8 @@ let system_mt = {
 	-- If this is called on a subsystem instead of the world, be warned that this will bypass all the parent's systems filters.
 	-- Since :remove will not search for entities in systems where they should have been filtered out, the added entities will not be removed
 	-- when calling :remove on a parent system or the world. The entity can only be removed by calling :remove on the system :add was called on.
-	add = :(...)
+	add = :(e, ...)
-		for _, e in ipairs({...}) do
+		if e ~= nil and @filter(e) then
-			if @filter(e) then
 			if @_first == nil then
 				@_first = { e, nil }
 			elseif @compare(e, @_first[1]) then
@@ -135,14 +136,16 @@ let system_mt = {
 			@entityCount += 1
 			@onAdd(e)
 		end
+		if ... then
+			return e, @add(...)
+		else
+			return e
 		end
-		return ...
 	end,
 	--- Remove entities to the system and its subsystems.
 	-- If you intend to call this on a subsystem instead of the world, please read the warning in :add.
-	remove = :(...)
+	remove = :(e, ...)
-		for _, e in ipairs({...}) do
+		if e ~= nil and @filter(e) then
-			if @filter(e) then
 			let found = false
 			if @_first == nil then
 				return
@@ -168,6 +171,10 @@ let system_mt = {
 				@onRemove(e)
 			end
 		end
+		if ... then
+			return e, @remove(...)
+		else
+			return e
 		end
 	end,
 	--- Returns an iterator that iterate through the entties in this system.
@@ -300,9 +307,31 @@ let any = (...)
 	end
 end
 
+let scene = (name, systems={}, entities={})
+	let s = newScene(name)
+	let w
+
+	function s:enter()
+		w = world(unpack(systems))
+		w:add(unpack(entities))
+	end
+	function s:exit()
+		w:destroy()
+	end
+	function s:update(dt)
+		w:update(dt)
+	end
+	function s:draw()
+		w:draw()
+	end
+
+	return s
+end
+
 --- ECS module.
 return {
 	world = world,
 	all = all,
-	any = any
+	any = any,
+	scene = scene
 }

scene/scene.lua

@@ -1,6 +1,6 @@
 --- ubiquitousse.scene
 -- Optional dependencies: ubiquitousse.time (to provide each scene a time registry)
-local loaded, time = pcall(require, (...):match("^.-ubiquitousse%.").."time")
+local loaded, time = pcall(require, (...):match("^(.-)scene").."time")
 if not loaded then time = nil end
 
 --- Scene management.

time/time.lua

@@ -1,6 +1,5 @@
 --- ubiquitousse.time
 -- Depends on a backend.
-
 local ease = require((...):match("^.-time")..".easing")
 local time