MonoGame.Extended/Source/Demos/StarWarrior/Systems/HudRenderSystem.cs

// Original code dervied from:
// https://github.com/thelinuxlich/starwarrior_CSharp/blob/master/StarWarrior/StarWarrior/Systems/HudRenderSystem.cs

// --------------------------------------------------------------------------------------------------------------------
// <copyright file="HudRenderSystem.cs" company="GAMADU.COM">
//     Copyright © 2013 GAMADU.COM. All rights reserved.
//
//     Redistribution and use in source and binary forms, with or without modification, are
//     permitted provided that the following conditions are met:
//
//        1. Redistributions of source code must retain the above copyright notice, this list of
//           conditions and the following disclaimer.
//
//        2. Redistributions in binary form must reproduce the above copyright notice, this list
//           of conditions and the following disclaimer in the documentation and/or other materials
//           provided with the distribution.
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//     THIS SOFTWARE IS PROVIDED BY GAMADU.COM 'AS IS' AND ANY EXPRESS OR IMPLIED
//     WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
//     FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GAMADU.COM OR
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// </copyright>
// <summary>
//   The hud render system.
// </summary>
// --------------------------------------------------------------------------------------------------------------------


using System;
using System.Text;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using MonoGame.Extended.BitmapFonts;
using MonoGame.Extended.Entities;
using MonoGame.Extended.Entities.Systems;
using StarWarrior.Components;

namespace StarWarrior.Systems
{
    public class HudRenderSystem : EntityDrawSystem
    {
        private readonly GraphicsDevice _graphicsDevice;
        private readonly BitmapFont _font;
        private readonly SpriteBatch _spriteBatch;
        private readonly StringBuilder _stringBuilder = new StringBuilder();


        public HudRenderSystem(GraphicsDevice graphicsDevice, SpriteBatch spriteBatch, BitmapFont font) 
            : base(Aspect.All(typeof(PlayerComponent), typeof(HealthComponent)))
        {
            _graphicsDevice = graphicsDevice;
            _spriteBatch = spriteBatch;
            _font = font;
        }

        public override void Initialize(IComponentMapperService mapperService)
        {
        }

        public override void Draw(GameTime gameTime)
        {
            foreach (var entityId in ActiveEntities)
            {
                var entity = GetEntity(entityId);
                var player = entity.Get<PlayerComponent>();
                var health = entity.Get<HealthComponent>();

                var viewport = _graphicsDevice.Viewport;
                var renderPosition = new Vector2(20, viewport.Height - 40);

                _stringBuilder.Clear();
                _stringBuilder.Append("Health: ");
                _stringBuilder.Append((float)Math.Round(health.Ratio * 100, 1));
                _stringBuilder.Append("%");

                _spriteBatch.DrawString(_font, _stringBuilder, renderPosition, Color.White);
            }
        }
    }
}