refactor: update & draw calls have been refactored into systems

Engine.Core/Systems/DrawManager.cs

@@ -0,0 +1,49 @@
+
+namespace Syntriax.Engine.Core;
+
+public class DrawManager : UniverseObject
+{
+    private readonly BehaviourCollector<IPreDraw> preDrawEntities = new();
+    private readonly BehaviourCollector<IDraw> drawEntities = new();
+    private readonly BehaviourCollector<IPostDraw> postDrawEntities = new();
+
+    private void OnPreDraw(IUniverse sender)
+    {
+        for (int i = preDrawEntities.Behaviours.Count - 1; i >= 0; i--)
+            preDrawEntities.Behaviours[i].PreDraw();
+    }
+
+    private void OnDraw(IUniverse sender)
+    {
+        for (int i = drawEntities.Behaviours.Count - 1; i >= 0; i--)
+            drawEntities.Behaviours[i].Draw();
+    }
+
+    private void OnPostDraw(IUniverse sender)
+    {
+        for (int i = postDrawEntities.Behaviours.Count - 1; i >= 0; i--)
+            postDrawEntities.Behaviours[i].PostDraw();
+    }
+
+    protected override void OnEnteringUniverse(IUniverse universe)
+    {
+        preDrawEntities.Assign(universe);
+        drawEntities.Assign(universe);
+        postDrawEntities.Assign(universe);
+
+        universe.OnPreDraw += OnPreDraw;
+        universe.OnDraw += OnDraw;
+        universe.OnPostDraw += OnPostDraw;
+    }
+
+    protected override void OnExitingUniverse(IUniverse universe)
+    {
+        preDrawEntities.Unassign();
+        drawEntities.Unassign();
+        postDrawEntities.Unassign();
+
+        universe.OnPreDraw -= OnPreDraw;
+        universe.OnDraw -= OnDraw;
+        universe.OnPostDraw -= OnPostDraw;
+    }
+}