sneak/Shared/ShmupWorld.cs

using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using System;
using System.Collections.Generic;

namespace SemiColinGames {
  public sealed class ShmupWorld : IWorld {
    public class ShmupPlayer {
      public TextureRef Texture = Textures.Yellow2;
      // Center of player sprite.
      public Vector2 Position = new Vector2(48, 1080 / 8);
      // TODO: use a bounds rect instead of HalfSize.
      public Vector2 HalfSize = new Vector2(16, 10);

      private float speed = 150f;
      private float shotCooldown = 0f;
      private ProfilingList<Shot> shots = new ProfilingList<Shot>(10, "playerShots");

      public ProfilingList<Shot> Update(
          float modelTime, History<Input> input, Rectangle worldBounds) {
        // Movement update.
        Vector2 motion = Vector2.Multiply(input[0].Motion, modelTime * speed);
        Position = Vector2.Add(Position, motion);
        Position.X = Math.Max(Position.X, HalfSize.X);
        Position.X = Math.Min(Position.X, worldBounds.Size.X - HalfSize.X);
        Position.Y = Math.Max(Position.Y, HalfSize.Y);
        Position.Y = Math.Min(Position.Y, worldBounds.Size.Y - HalfSize.Y);

        // Check whether we need to add new shots.
        shotCooldown -= modelTime;
        shots.Clear();
        if (input[0].Attack && shotCooldown <= 0) {
          shotCooldown = 0.2f;
          Vector2 shotOffset = new Vector2(12, 2);
          Vector2 shotPosition = Vector2.Add(Position, shotOffset);
          shots.Add(new Shot(shotPosition, new Vector2(300, 0)));
        }
        return shots;
      }

      public void Draw(SpriteBatch spriteBatch) {
        Texture2D texture = Texture.Get;
        Vector2 spriteCenter = new Vector2(texture.Width / 2, texture.Height / 2);
        Vector2 drawPos = Vector2.Floor(Vector2.Subtract(Position, spriteCenter));
        spriteBatch.Draw(texture, drawPos, Color.White);
      }
    }

    public class Shot {
      static int color = 0;
      public TextureRef Texture;
      public Vector2 Position;
      public Vector2 HalfSize = new Vector2(11, 4);
      public Rectangle Bounds;
      public Vector2 Velocity;
      public Shot(Vector2 position, Vector2 velocity) {
        Texture = (color % 5) switch {
          0 => Textures.Projectile1,
          1 => Textures.Projectile2,
          2 => Textures.Projectile3,
          3 => Textures.Projectile4,
          _ => Textures.Projectile5
        };
        color++;

        Position = position;
        Velocity = velocity;
        Update(0);  // set Bounds
      }

      public void Update(float modelTime) {
        Position = Vector2.Add(Position, Vector2.Multiply(Velocity, modelTime));
        Bounds = new Rectangle(
            (int) (Position.X - HalfSize.X),
            (int) (Position.Y - HalfSize.Y),
            (int) HalfSize.X * 2,
            (int) HalfSize.Y * 2);
      }

      public void Draw(SpriteBatch spriteBatch) {
        Texture2D texture = Texture.Get;
        Vector2 center = new Vector2(texture.Width / 2, texture.Height / 2);
        spriteBatch.Draw(texture, Vector2.Floor(Vector2.Subtract(Position, center)), Color.White);
      }
    }

    public readonly Rectangle Bounds;
    public readonly ShmupPlayer Player;
    public readonly ProfilingList<Shot> Shots;

    public ShmupWorld() {
      Bounds = new Rectangle(0, 0, 1920 / 4, 1080 / 4);
      Player = new ShmupPlayer();
      Shots = new ProfilingList<Shot>(100, "shots");
    }

    ~ShmupWorld() {
      Dispose();
    }

    public void Dispose() {
      GC.SuppressFinalize(this);
    }

    public void Update(float modelTime, History<Input> input) {
      // Update player & shots.
      ProfilingList<Shot> newPlayerShots = Player.Update(modelTime, input, Bounds);
      foreach (Shot shot in Shots) {
        shot.Update(modelTime);
      }

      // Add new shots.
      Shots.AddRange(newPlayerShots);

      // Reap off-screen objects.
      Rectangle paddedBounds = Bounds;
      paddedBounds.Inflate(16, 16);
      Shots.RemoveAll(shot => !paddedBounds.Intersects(shot.Bounds));

      Debug.AddToast("shots: " + Shots.Count);
    }
  }
}