EXPERIMENTAL: Metal backend (#441)

This is not a continuation of the Metal backend; this is simply bringing
the branch up to date and merging it as-is behind an experiment.

---------

Co-authored-by: Isaac Marovitz <isaacryu@icloud.com>
Co-authored-by: Samuliak <samuliak77@gmail.com>
Co-authored-by: SamoZ256 <96914946+SamoZ256@users.noreply.github.com>
Co-authored-by: Isaac Marovitz <42140194+IsaacMarovitz@users.noreply.github.com>
Co-authored-by: riperiperi <rhy3756547@hotmail.com>
Co-authored-by: Gabriel A <gab.dark.100@gmail.com>

src/Ryujinx.Graphics.Metal/TextureBase.cs

@@ -0,0 +1,67 @@
+using Ryujinx.Graphics.GAL;
+using SharpMetal.Metal;
+using System;
+using System.Runtime.Versioning;
+using System.Threading;
+
+namespace Ryujinx.Graphics.Metal
+{
+    [SupportedOSPlatform("macos")]
+    abstract class TextureBase : IDisposable
+    {
+        private int _isValid = 1;
+
+        public bool Valid => Volatile.Read(ref _isValid) != 0;
+
+        protected readonly Pipeline Pipeline;
+        protected readonly MTLDevice Device;
+        protected readonly MetalRenderer Renderer;
+
+        protected MTLTexture MtlTexture;
+
+        public readonly TextureCreateInfo Info;
+        public int Width => Info.Width;
+        public int Height => Info.Height;
+        public int Depth => Info.Depth;
+
+        public MTLPixelFormat MtlFormat { get; protected set; }
+        public int FirstLayer { get; protected set; }
+        public int FirstLevel { get; protected set; }
+
+        public TextureBase(MTLDevice device, MetalRenderer renderer, Pipeline pipeline, TextureCreateInfo info)
+        {
+            Device = device;
+            Renderer = renderer;
+            Pipeline = pipeline;
+            Info = info;
+        }
+
+        public MTLTexture GetHandle()
+        {
+            if (_isValid == 0)
+            {
+                return new MTLTexture(IntPtr.Zero);
+            }
+
+            return MtlTexture;
+        }
+
+        public virtual void Release()
+        {
+            Dispose();
+        }
+
+        public void Dispose()
+        {
+            bool wasValid = Interlocked.Exchange(ref _isValid, 0) != 0;
+
+            if (wasValid)
+            {
+                if (MtlTexture != IntPtr.Zero)
+                {
+                    MtlTexture.Dispose();
+                }
+            }
+        }
+    }
+}