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; }
+}

Engine.Systems/Graphics/IDrawableTriangle.cs

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+using Engine.Core;
+
+namespace Engine.Systems.Graphics;
+
+public interface IDrawableTriangle : IBehaviour
+{
+    void Draw(ITriangleBatch triangleBatch);
+}

Engine.Systems/Graphics/ITriangleBatch.cs

@@ -0,0 +1,10 @@
+using Engine.Core;
+
+namespace Engine.Systems.Graphics;
+
+public interface ITriangleBatch
+{
+    void Begin(Matrix4x4? view = null, Matrix4x4? projection = null);
+    void Draw(Triangle triangle, ColorRGBA colorRGBA);
+    void End();
+}

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();
+    }
+}