sneak/Shared/NPC.cs

using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;

namespace SemiColinGames {
  class NPC {
    private Point position;

    private const int spriteWidth = 96;
    private const int spriteHeight = 81;
    private const int spriteCenterYOffset = 3;

    public NPC(Point position) {
      this.position = position;
    }

    public int Facing { get; private set; } = 1;

    public void Update(float modelTime) {
      if (Facing == 1 && position.X > 16 * 39) {
        Facing = -1;
      }
      if (Facing == -1 && position.X < 16 * 24) {
        Facing = 1;
      }
      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);
      Vector2 spriteCenter = new Vector2(spriteWidth / 2, spriteHeight / 2 + spriteCenterYOffset);
      SpriteEffects effect = Facing == 1 ?
        SpriteEffects.None : SpriteEffects.FlipHorizontally;
      Color color = Color.White;
      spriteBatch.Draw(Textures.Executioner.Get, position.ToVector2(), textureSource, color, 0f,
        spriteCenter, Vector2.One, effect, 0f);
    }
  }
}