gaemstone/src/gaemstone.Client/Systems/TextureManager.cs

using System;
using System.IO;
using gaemstone.ECS;
using gaemstone.Flecs;
using Silk.NET.OpenGL;
using SixLabors.ImageSharp;
using SixLabors.ImageSharp.PixelFormats;
using static gaemstone.Client.Components.RenderingComponents;
using static gaemstone.Client.Systems.Windowing;
using Texture = gaemstone.Client.Components.ResourceComponents.Texture;

namespace gaemstone.Client.Systems;

[Module]
[DependsOn<gaemstone.Client.Components.RenderingComponents>]
[DependsOn<gaemstone.Client.Components.ResourceComponents>]
[DependsOn<gaemstone.Client.Systems.Windowing>]
public class TextureManager
{
	[Observer<ObserverEvent.OnSet>]
	public static void OnCanvasSet(Canvas canvas)
	{
		var GL = 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(0xFF);
		GL.TexImage2D(TextureTarget.Texture2D, 0, InternalFormat.Rgba,
		              1, 1, 0, PixelFormat.Rgba, PixelType.UnsignedByte, in pixel[0]);
	}

	[System]
	public static void LoadTextureWhenDefined(
		[Game] Canvas canvas, EntityRef entity,
		Texture _1, [Not] TextureHandle _2)
	{
		var path = entity.GetFullPath();
		using var stream = Resources.GetStream(path);
		var handle = CreateFromStream(canvas.GL, stream);
		entity.Set(handle);
	}

	private static TextureHandle CreateFromStream(GL GL, Stream stream)
	{
		var target = TextureTarget.Texture2D;
		var handle = GL.GenTexture();
		GL.BindTexture(target, handle);

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

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

		GL.BindTexture(target, 0);
		return new(target, handle);
	}
}