refactor: moved drawable triangles into systems project for platform agnosticism

Engine.Systems/Graphics/TriangleBatcher.cs

@@ -0,0 +1,33 @@
+using System.Collections.Generic;
+
+using Engine.Core;
+
+namespace Engine.Systems.Graphics;
+
+public class TriangleBatcher : Behaviour, IFirstFrameUpdate, IDraw
+{
+    private static Comparer<int> SortByAscendingPriority() => Comparer<int>.Create((x, y) => x.CompareTo(y));
+    private static System.Func<IBehaviour, int> GetPriority() => (b) => b.Priority;
+
+    private ITriangleBatch triangleBatch = null!;
+    private ICamera camera = null!;
+
+    private readonly ActiveBehaviourCollectorOrdered<int, IDrawableTriangle> drawableShapes = new(GetPriority(), SortByAscendingPriority());
+
+    public void FirstActiveFrame()
+    {
+        camera = Universe.FindRequiredBehaviour<ICamera>();
+
+        triangleBatch = Universe.FindRequiredBehaviour<ITriangleBatch>();
+        drawableShapes.Unassign();
+        drawableShapes.Assign(Universe);
+    }
+
+    public void Draw()
+    {
+        triangleBatch.Begin(camera.ViewMatrix, camera.ProjectionMatrix);
+        for (int i = 0; i < drawableShapes.Count; i++)
+            drawableShapes[i].Draw(triangleBatch);
+        triangleBatch.End();
+    }
+}