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/SamplerHolder.cs

@@ -0,0 +1,90 @@
+using Ryujinx.Graphics.GAL;
+using SharpMetal.Metal;
+using System;
+using System.Runtime.Versioning;
+
+namespace Ryujinx.Graphics.Metal
+{
+    [SupportedOSPlatform("macos")]
+    class SamplerHolder : ISampler
+    {
+        private readonly MetalRenderer _renderer;
+        private readonly Auto<DisposableSampler> _sampler;
+
+        public SamplerHolder(MetalRenderer renderer, MTLDevice device, SamplerCreateInfo info)
+        {
+            _renderer = renderer;
+
+            renderer.Samplers.Add(this);
+
+            (MTLSamplerMinMagFilter minFilter, MTLSamplerMipFilter mipFilter) = info.MinFilter.Convert();
+
+            MTLSamplerBorderColor borderColor = GetConstrainedBorderColor(info.BorderColor, out _);
+
+            using var descriptor = new MTLSamplerDescriptor
+            {
+                BorderColor = borderColor,
+                MinFilter = minFilter,
+                MagFilter = info.MagFilter.Convert(),
+                MipFilter = mipFilter,
+                CompareFunction = info.CompareOp.Convert(),
+                LodMinClamp = info.MinLod,
+                LodMaxClamp = info.MaxLod,
+                LodAverage = false,
+                MaxAnisotropy = Math.Max((uint)info.MaxAnisotropy, 1),
+                SAddressMode = info.AddressU.Convert(),
+                TAddressMode = info.AddressV.Convert(),
+                RAddressMode = info.AddressP.Convert(),
+                SupportArgumentBuffers = true
+            };
+
+            var sampler = device.NewSamplerState(descriptor);
+
+            _sampler = new Auto<DisposableSampler>(new DisposableSampler(sampler));
+        }
+
+        private static MTLSamplerBorderColor GetConstrainedBorderColor(ColorF arbitraryBorderColor, out bool cantConstrain)
+        {
+            float r = arbitraryBorderColor.Red;
+            float g = arbitraryBorderColor.Green;
+            float b = arbitraryBorderColor.Blue;
+            float a = arbitraryBorderColor.Alpha;
+
+            if (r == 0f && g == 0f && b == 0f)
+            {
+                if (a == 1f)
+                {
+                    cantConstrain = false;
+                    return MTLSamplerBorderColor.OpaqueBlack;
+                }
+
+                if (a == 0f)
+                {
+                    cantConstrain = false;
+                    return MTLSamplerBorderColor.TransparentBlack;
+                }
+            }
+            else if (r == 1f && g == 1f && b == 1f && a == 1f)
+            {
+                cantConstrain = false;
+                return MTLSamplerBorderColor.OpaqueWhite;
+            }
+
+            cantConstrain = true;
+            return MTLSamplerBorderColor.OpaqueBlack;
+        }
+
+        public Auto<DisposableSampler> GetSampler()
+        {
+            return _sampler;
+        }
+
+        public void Dispose()
+        {
+            if (_renderer.Samplers.Remove(this))
+            {
+                _sampler.Dispose();
+            }
+        }
+    }
+}