make tile-texture lookup dictioanry-based instead of switch-based

GitOrigin-RevId: 2f0c215bf9e79e92f2c7a5011d8df3d9d80a0dff

Shared/World.cs

@@ -20,6 +20,18 @@ namespace SemiColinGames {
     readonly Texture2D texture;
     readonly Rectangle textureSource;
 
+    static readonly Dictionary<Terrain, Point> terrainToTilePosition =
+        new Dictionary<Terrain, Point>() {
+      { Terrain.Grass, new Point(3, 0) },
+      { Terrain.GrassL, new Point(2, 0) },
+      { Terrain.GrassR, new Point(4, 0) },
+      { Terrain.Rock, new Point(3, 1) },
+      { Terrain.RockL, new Point(1, 2) },
+      { Terrain.RockR, new Point(5, 2) },
+      { Terrain.Water, new Point(9, 2) },
+      { Terrain.Block, new Point(6, 3) },
+    };
+
     public Tile(Texture2D texture, Terrain terrain, Rectangle position) {
       this.texture = texture;
       Terrain = terrain;
@@ -37,27 +49,8 @@ namespace SemiColinGames {
 
     private Rectangle TextureSource() {
       int size = World.TileSize;
-      switch (Terrain) {
+      Point pos = terrainToTilePosition[Terrain];
-        case Terrain.Grass:
+      return new Rectangle(pos.X * size, pos.Y * size, size, size);
-            return new Rectangle(3 * size, 0 * size, size, size);
-        case Terrain.GrassL:
-            return new Rectangle(2 * size, 0 * size, size, size);
-        case Terrain.GrassR:
-          return new Rectangle(4 * size, 0 * size, size, size);
-        case Terrain.Rock:
-          return new Rectangle(3 * size, 1 * size, size, size);
-        case Terrain.RockL:
-          return new Rectangle(1 * size, 2 * size, size, size);
-        case Terrain.RockR:
-          return new Rectangle(5 * size, 2 * size, size, size);
-        case Terrain.Water:
-          return new Rectangle(9 * size, 2 * size, size, size);
-        case Terrain.Block:
-          return new Rectangle(6 * size, 3 * size, size, size);
-        default:
-          Debug.WriteLine("Tile.TextureSource(): rectangle not found");
-          return new Rectangle();
-      }
     }
   }