Fix MathUtils.LerpVector2, add cameras.

DaggerFramework/Source/SceneGraph/EntityLayer.cs

@@ -1,10 +1,13 @@
 using DaggerFramework.Rendering;
+using DaggerFramework.Utils;
 
 namespace DaggerFramework.SceneGraph
 {
     public class EntityLayer : Layer
     {
         public List<Entity> Entities { get => _entities; }
+        public Camera2d CurrentCamera { get; set; }
+
         public EntityLayer(List<Entity> entities)
         {
             _entities = entities;
@@ -15,11 +18,36 @@ namespace DaggerFramework.SceneGraph
             _entities = new List<Entity>();
         }
 
+        public void UpdateCurrentCamera()
+        {
+            if (_cameraEntities.Count == 1)
+            {
+                CurrentCamera = _cameraEntities[0];
+                return;
+            }
+            else
+            {
+                foreach (var camera in _cameraEntities)
+                {
+                    if (camera.Current) CurrentCamera = camera;
+                }
+            }
+        }
+
         public bool AddEntity(Entity entity)
         {
             entity.Id = Entities.Count;
             entity.Layer = this;
+
+            if (entity is Camera2d camera2d)
+            {
+                _cameraEntities.Add(camera2d);
+                UpdateCurrentCamera();
+            }
+
             Entities.Add(entity);
+
+
             return true;
         }
 
@@ -30,8 +58,9 @@ namespace DaggerFramework.SceneGraph
 
         protected override void OnStart()
         {
-            foreach (var entity in _entities)
+            for (int i = 0; i < _entities.Count; i++)
             {
+                var entity = _entities[i];
                 entity.Layer = this;
                 entity.Start();
             }
@@ -45,14 +74,38 @@ namespace DaggerFramework.SceneGraph
             }
         }
 
+        protected override void OnBeginDraw(Renderer renderer)
+        {
+            var hasCamera = CurrentCamera != null;
+            if (hasCamera)
+            {
+                renderer.BeginCamera2d(CurrentCamera.Offset, CurrentCamera.Position, 0f, CurrentCamera.Zoom);
+            }
+        }
+
+        protected override void OnEndDraw(Renderer renderer)
+        {
+            var hasCamera = CurrentCamera != null;
+            if (hasCamera)
+            {
+                renderer.EndCamera2d();
+            }
+        }
+
+
         protected override void OnDraw(Renderer renderer)
         {
-            foreach (IDrawable drawable in _entities)
+            // TODO: can be done more efficiently, needs rendering redesign.
+            foreach (var entity in _entities)
             {
-                drawable.Draw(renderer);
+                if (entity is IDrawable drawable)
+                {
+                    drawable.Draw(renderer);
+                }
             }
         }
 
         private List<Entity> _entities;
+        private List<Camera2d> _cameraEntities = new();
     }
 }