refactor: moved drawable triangles into systems project for platform agnosticism

Engine.Systems/Graphics/DrawableShape2D.cs

@@ -0,0 +1,29 @@
+using System.Collections.Generic;
+
+using Engine.Core;
+
+namespace Engine.Systems.Graphics;
+
+public class DrawableShape2D : Behaviour2D, IDrawableTriangle, IPreDraw
+{
+    private readonly Shape2D shape = new([]);
+    private readonly List<Triangle> worldTriangles = [];
+    private readonly Shape2D worldShape = new([]);
+    protected ColorRGB color = new(255, 255, 255);
+
+    public void PreDraw() => UpdateWorldShape();
+
+    public void Draw(ITriangleBatch triangleBatch)
+    {
+        worldShape.ToTrianglesConvex(worldTriangles);
+
+        foreach (Triangle triangle in worldTriangles)
+            triangleBatch.Draw(new(triangle.C, triangle.B, triangle.A), color);
+    }
+
+    protected void UpdateWorldShape() => shape.Transform(Transform, worldShape);
+
+    public DrawableShape2D() => shape = Shape2D.Triangle;
+    public DrawableShape2D(Shape2D shape) => this.shape = shape;
+    public DrawableShape2D(Shape2D shape, ColorRGB color) { this.shape = shape; this.color = color; }
+}