make CollisionTargets an array, and don't recompute it every frame

GitOrigin-RevId: 92a02231ed

Shared/Player.cs

@@ -33,7 +33,7 @@ namespace SemiColinGames {
       return new Rectangle(position.X - spriteWidth, position.Y - 7, spriteWidth * 2, 26);
     }
 
-    public void Update(float modelTime, History<Input> input, List<Rectangle> collisionTargets) {
+    public void Update(float modelTime, History<Input> input, Rectangle[] collisionTargets) {
       Point oldPosition = position;
       Vector2 movement = HandleInput(modelTime, input);
       position = new Point((int) (oldPosition.X + movement.X), (int) (oldPosition.Y + movement.Y));

Shared/SneakGame.cs

@@ -93,7 +93,7 @@ namespace SemiColinGames {
       if (!paused) {
         float modelTime = (float) gameTime.ElapsedGameTime.TotalSeconds;
         Clock.AddModelTime(modelTime);
-        List<Rectangle> collisionTargets = world.CollisionTargets();
+        Rectangle[] collisionTargets = world.CollisionTargets;
         player.Update(modelTime, input, collisionTargets);
         camera.Update(player.Position);
       }

Shared/World.cs

@@ -82,7 +82,8 @@ namespace SemiColinGames {
   class World {
 
     public const int TileSize = 16;
-    readonly List<Tile> tiles = new List<Tile>();
+    readonly Tile[] tiles;
+    readonly Rectangle[] collisionTargets;
 
     public int Width { get; private set; }
     public int Height { get; private set; }
@@ -106,6 +107,7 @@ namespace SemiColinGames {
 ....................] [............................................]  [.............]   [..............................................................]  [.......................................................";
 
     public World(Texture2D texture) {
+      var tilesList = new List<Tile>();
       string[] worldDesc = worldString.Split('\n');
       Width = worldDesc.AsQueryable().Max(a => a.Length);
       Height = worldDesc.Length;
@@ -146,10 +148,15 @@ namespace SemiColinGames {
           }
           if (terrain != Terrain.Empty) {
             var position = new Rectangle(i * TileSize, j * TileSize, TileSize, TileSize);
-            tiles.Add(new Tile(texture, terrain, position));
+            tilesList.Add(new Tile(texture, terrain, position));
           }
         }
       }
+      tiles = tilesList.ToArray();
+      collisionTargets = new Rectangle[tiles.Length];
+      for (int i = 0; i < tiles.Length; i++) {
+        collisionTargets[i] = tiles[i].Position;
+      }
     }
 
     public void Draw(SpriteBatch spriteBatch, Camera camera) {
@@ -158,12 +165,8 @@ namespace SemiColinGames {
       }
     }
 
-    public List<Rectangle> CollisionTargets() {
-      var result = new List<Rectangle>();
-      foreach (Tile t in tiles) {
-        result.Add(t.Position);
-      }
-      return result;
+    public Rectangle[] CollisionTargets {
+      get { return collisionTargets; }
     }
   }
 }