gaemstone/src/gaemstone.Client/TextureManager.cs

using System;
using System.Collections.Generic;
using System.IO;
using gaemstone.ECS;
using Silk.NET.OpenGL;
using SixLabors.ImageSharp;
using SixLabors.ImageSharp.PixelFormats;
using Size = System.Drawing.Size;

namespace gaemstone.Client;

public static class TextureManager
{
	private static readonly Dictionary<Texture, TextureInfo> _byTexture = new();
	private static readonly Dictionary<string, TextureInfo> _bySourceFile = new();

	public static void Initialize(Universe universe)
	{
		var GL = universe.Lookup<Game>().Get<Windowing.Canvas>().GL;
		// Upload single-pixel white texture into texture slot 0, so when
		// "no" texture is bound, we can still use the texture sampler.
		GL.BindTexture(TextureTarget.Texture2D, 0);
		Span<byte> pixel = stackalloc byte[4];
		pixel.Fill(255);
		GL.TexImage2D(TextureTarget.Texture2D, 0, InternalFormat.Rgba,
		              1, 1, 0, PixelFormat.Rgba, PixelType.UnsignedByte, in pixel[0]);
		GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMagFilter, (int)TextureMagFilter.Nearest);
		GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMinFilter, (int)TextureMinFilter.Nearest);
	}

	public static Texture Load(Universe universe, string name)
	{
		using var stream = Resources.GetStream(name);
		return CreateFromStream(universe, stream, name);
	}

	public static Texture CreateFromStream(Universe universe, Stream stream, string? sourceFile = null)
	{
		var GL = universe.Lookup<Game>().Get<Windowing.Canvas>().GL;
		var texture = new Texture(TextureTarget.Texture2D, GL.GenTexture());
		GL.BindTexture(texture.Target, texture.Handle);

		var image = Image.Load<Rgba32>(stream);
		ref var origin = ref image.Frames[0].PixelBuffer[0, 0];

		GL.TexImage2D(texture.Target, 0, (int)PixelFormat.Rgba,
		              (uint)image.Width, (uint)image.Height, 0,
		              PixelFormat.Rgba, PixelType.UnsignedByte, origin);
		GL.TexParameter(texture.Target, TextureParameterName.TextureMagFilter, (int)TextureMagFilter.Nearest);
		GL.TexParameter(texture.Target, TextureParameterName.TextureMinFilter, (int)TextureMinFilter.Nearest);

		var info = new TextureInfo(texture, sourceFile, new(image.Width, image.Height));
		_byTexture.Add(texture, info);
		if (sourceFile != null) _bySourceFile.Add(sourceFile, info);

		GL.BindTexture(texture.Target, 0);
		return texture;
	}


	public static TextureInfo? Lookup(Texture texture)
		=> _byTexture.TryGetValue(texture, out var value) ? value : null;

	public static TextureInfo? Lookup(string sourceFile)
		=> _bySourceFile.TryGetValue(sourceFile, out var value) ? value : null;
}

public class TextureInfo
{
	public Texture Texture { get; }
	public string? SourceFile { get; }
	public Size Size { get; }

	public TextureInfo(Texture texture, string? sourceFile, Size size)
		=> (Texture, SourceFile, Size) = (texture, sourceFile, size);
}