sneak/Shared/ShmupScene.cs

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

namespace SemiColinGames {
  public sealed class ShmupScene : IScene {

    const float DESIRED_ASPECT_RATIO = 1920.0f / 1080.0f;

    private readonly Color letterboxColor = Color.DarkSlateBlue;
    private readonly Color backgroundColor = Color.Black;

    private readonly GraphicsDevice graphics;
    private readonly RenderTarget2D sceneTarget;
    private readonly SpriteBatch spriteBatch;

    public ShmupScene(GraphicsDevice graphics, Point worldSize) {
      this.graphics = graphics;

      sceneTarget = new RenderTarget2D(
        graphics, worldSize.X, worldSize.Y, false /* mipmap */,
        graphics.PresentationParameters.BackBufferFormat, DepthFormat.Depth24);
      spriteBatch = new SpriteBatch(graphics);
    }

    ~ShmupScene() {
      Dispose();
    }

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

    public void Draw(bool isRunningSlowly, IWorld iworld, bool paused) {
      ShmupWorld world = (ShmupWorld) iworld;

      // Draw scene to sceneTarget.
      graphics.SetRenderTarget(sceneTarget);
      graphics.Clear(backgroundColor);

      spriteBatch.Begin(SpriteSortMode.Deferred, BlendState.AlphaBlend,
          SamplerState.PointClamp, DepthStencilState.Default,
          RasterizerState.CullNone);

      // Draw enemies, then player, then shots.
      foreach (ShmupWorld.Enemy e in world.Enemies) {
        e.Draw(spriteBatch);
      }

      world.Player.Draw(spriteBatch);

      foreach (ShmupWorld.Shot s in world.Shots) {
        s.Draw(spriteBatch);
      }

      // Finish drawing sprites.
      spriteBatch.End();

      // Get ready to draw sceneTarget to screen.
      graphics.SetRenderTarget(null);
      graphics.Clear(letterboxColor);

      // Letterbox the scene if needed.
      float aspectRatio = 1.0f * graphics.Viewport.Width / graphics.Viewport.Height;
      Rectangle drawRect;
      if (aspectRatio > DESIRED_ASPECT_RATIO) {
        // Need to letterbox the sides.
        int desiredWidth = (int) (graphics.Viewport.Height * DESIRED_ASPECT_RATIO);
        int padding = (graphics.Viewport.Width - desiredWidth) / 2;
        drawRect = new Rectangle(padding, 0, desiredWidth, graphics.Viewport.Height);
      } else {
        // Need to letterbox the top / bottom.
        int desiredHeight = (int) (graphics.Viewport.Width / DESIRED_ASPECT_RATIO);
        int padding = (graphics.Viewport.Height - desiredHeight) / 2;
        drawRect = new Rectangle(0, padding, graphics.Viewport.Width, desiredHeight);
      }

      // Actually draw to screen.
      spriteBatch.Begin(SpriteSortMode.Deferred, BlendState.AlphaBlend,
          SamplerState.PointClamp, DepthStencilState.Default,
          RasterizerState.CullNone);
      spriteBatch.Draw(sceneTarget, drawRect, Color.White);

      // Draw debug toasts.
      Debug.DrawToasts(spriteBatch);

      spriteBatch.End();
    }
  }
}