Add Sprite class & load sprite metadata from JSON.

Shared/NPC.cs

@@ -25,14 +25,10 @@ namespace SemiColinGames {
       position.X += (int) (120 * Facing * modelTime);
     }
 
-    private int SpriteIndex() {
-      int frameNum = (int) Clock.ModelTime.TotalMilliseconds / 125 % 4;
-      return 35 + frameNum;
-    }
-
     public void Draw(SpriteBatch spriteBatch) {
-      int index = SpriteIndex();
-      Rectangle textureSource = new Rectangle(index * spriteWidth, 0, spriteWidth, spriteHeight);
+      Rectangle textureSource = Sprites.Executioner.GetTextureSource(
+          "run", (int) Clock.ModelTime.TotalMilliseconds);
+      // TODO: move this into Sprite metadata.
       Vector2 spriteCenter = new Vector2(spriteWidth / 2, spriteHeight / 2 + spriteCenterYOffset);
       SpriteEffects effect = Facing == 1 ?
         SpriteEffects.None : SpriteEffects.FlipHorizontally;

Shared/Shared.projitems

@@ -13,6 +13,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)ExtensionMethods.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)NPC.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)SoundEffects.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Sprites.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Text.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Textures.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Clock.cs" />

Shared/SneakGame.cs

@@ -61,6 +61,8 @@ namespace SemiColinGames {
       base.LoadContent();
       SoundEffects.Load(Content);
       Textures.Load(Content);
+      Sprites.Load(Content);
+      // TODO: move this into World.
       linesOfSight = new LinesOfSight(GraphicsDevice);
       LoadLevel();
     }

Shared/Sprites.cs

@@ -0,0 +1,89 @@
+using Microsoft.Xna.Framework;
+using Microsoft.Xna.Framework.Content;
+using Newtonsoft.Json.Linq;
+using System.Collections.Generic;
+
+namespace SemiColinGames {
+  struct SpriteAnimation {
+    public readonly int Start;
+    public readonly int End;
+    public readonly int DurationMs;
+
+    public SpriteAnimation(int start, int end, int durationMs) {
+      Start = start;
+      End = end;
+      DurationMs = durationMs;
+    }
+  }
+
+  struct Frame {
+    public readonly Rectangle Source;
+    public readonly int DurationMs;
+
+    public Frame(Rectangle source, int durationMs) {
+      Source = source;
+      DurationMs = durationMs;
+    }
+  }
+
+  class Sprite {
+    public readonly TextureRef Texture;
+
+    private readonly Dictionary<string, SpriteAnimation> animations;
+    private readonly List<Frame> frames;
+
+    public Sprite(TextureRef texture, string metadataJson) {
+      Texture = texture;
+      animations = new Dictionary<string, SpriteAnimation>();
+
+      JObject json = JObject.Parse(metadataJson);
+
+      frames = new List<Frame>();
+      foreach (JToken child in json.SelectToken("frames").Children()) {
+        Rectangle source = new Rectangle(
+            child.SelectToken("frame.x").Value<int>(),
+            child.SelectToken("frame.y").Value<int>(),
+            child.SelectToken("frame.w").Value<int>(),
+            child.SelectToken("frame.h").Value<int>());
+        int durationMs = child.SelectToken("duration").Value<int>();
+        frames.Add(new Frame(source, durationMs));
+      }
+
+      // TODO: handle ping-pong animations.
+      JToken frameTags = json.SelectToken("meta.frameTags");
+      foreach (JToken child in frameTags.Children()) {
+        string name = child.SelectToken("name").Value<string>();
+        int start = child.SelectToken("from").Value<int>();
+        int end = child.SelectToken("to").Value<int>();
+        int durationMs = 0;
+        for (int i = start; i <= end; i++) {
+          durationMs += frames[i].DurationMs;
+        }
+        animations[name] = new SpriteAnimation(start, end, durationMs);
+      }
+    }
+
+    public Rectangle GetTextureSource(string animationName, int timeMs) {
+      SpriteAnimation animation = animations[animationName];
+      int time = timeMs % animation.DurationMs;
+      for (int i = animation.Start; i <= animation.End; i++) {
+        int frameTime = frames[i].DurationMs;
+        if (time < frameTime) {
+          return frames[i].Source;
+        }
+        time -= frameTime;
+      }
+      // We shouldn't get here, but if we did, the last frame is a fine thing to return.
+      return frames[animation.End].Source;
+    }
+  }
+
+  static class Sprites {
+    public static Sprite Executioner;
+
+    public static void Load(ContentManager content) {
+      Executioner = new Sprite(
+          Textures.Executioner, content.Load<string>("sprites/ccg/executioner_female_json"));
+    }
+  }
+}