Sprite: keep track of Width and Height

Shared/NPC.cs

@@ -47,10 +47,7 @@ namespace SemiColinGames {
   }
 
   public class NPC {
-    // TODO: load sprite sizes from metadata.
-    private const int spriteWidth = 96;
-    private const int spriteHeight = 82;
-    private const int groundPadding = 7;
+    private readonly Sprite sprite;
     private readonly Vector2 spriteCenter;
     private readonly Vector2 eyeOffset = new Vector2(4, -9);
 
@@ -59,8 +56,10 @@ namespace SemiColinGames {
     private readonly Vector2 halfSize = new Vector2(12, 24);
 
     public NPC(Point position, int facing) {
+      sprite = Sprites.Executioner;
       Position = position;
-      spriteCenter = new Vector2(spriteWidth / 2, spriteHeight - halfSize.Y - groundPadding);
+      spriteCenter = new Vector2(
+          sprite.Width / 2, sprite.Height - halfSize.Y - sprite.GroundPadding);
       physicsBox = new AABB(position.ToVector2(), halfSize);
       Facing = facing;
       fsm = new FSM<NPC>(new Dictionary<string, IState<NPC>> {
@@ -104,8 +103,8 @@ namespace SemiColinGames {
     }
 
     public void Draw(SpriteBatch spriteBatch) {
-      Rectangle textureSource = Sprites.Executioner.GetTextureSource(
-          fsm.StateName, Clock.ModelTime.TotalSeconds);
+      Rectangle textureSource =
+          sprite.GetTextureSource(fsm.StateName, Clock.ModelTime.TotalSeconds);
       SpriteEffects effect = Facing == 1 ?
         SpriteEffects.None : SpriteEffects.FlipHorizontally;
       Color color = Color.White;

Shared/Sprites.cs

@@ -46,6 +46,12 @@ namespace SemiColinGames {
   }
 
   public class Sprite {
+    public readonly int Width;
+    public readonly int Height;
+    // Measures the empty pixels between the ground (where the sprite's feet rest in idle pose)
+    // and the bottom of the sprite's image.
+    public readonly int GroundPadding = 7;
+
     public readonly TextureRef Texture;
 
     private readonly Dictionary<string, SpriteAnimation> animations;
@@ -67,6 +73,10 @@ namespace SemiColinGames {
         double duration = child.SelectToken("duration").Value<double>() / 1000;
         frames.Add(new Frame(source, duration));
       }
+      // We assume that all frames are the same size (which right now is assured by the
+      // Aseprite-based spritesheet export process).
+      Width = frames[0].Source.Width;
+      Height = frames[0].Source.Height;
 
       JToken frameTags = json.SelectToken("meta.frameTags");
       foreach (JToken child in frameTags.Children()) {