Better index buffer management

src/Ryujinx.Graphics.Metal/IndexBufferState.cs

@@ -0,0 +1,74 @@
+using Ryujinx.Graphics.GAL;
+using SharpMetal.Metal;
+using System;
+using System.Runtime.Versioning;
+
+namespace Ryujinx.Graphics.Metal
+{
+    [SupportedOSPlatform("macos")]
+    internal struct IndexBufferState
+    {
+        public static IndexBufferState Null => new(BufferHandle.Null, 0, 0);
+
+        private readonly int _offset;
+        private readonly int _size;
+        private readonly IndexType _type;
+
+        private readonly BufferHandle _handle;
+
+        public IndexBufferState(BufferHandle handle, int offset, int size, IndexType type)
+        {
+            _handle = handle;
+            _offset = offset;
+            _size = size;
+            _type = type;
+        }
+
+        public IndexBufferState(BufferHandle handle, int offset, int size)
+        {
+            _handle = handle;
+            _offset = offset;
+            _size = size;
+            _type = IndexType.UInt;
+        }
+
+        public (MTLBuffer, int, MTLIndexType) GetIndexBuffer(MetalRenderer renderer, CommandBufferScoped cbs)
+        {
+            Auto<DisposableBuffer> autoBuffer;
+            int offset, size;
+            MTLIndexType type;
+
+            if (_type == IndexType.UByte)
+            {
+                // Index type is not supported. Convert to I16.
+                autoBuffer = renderer.BufferManager.GetBufferI8ToI16(cbs, _handle, _offset, _size);
+
+                type = MTLIndexType.UInt16;
+                offset = 0;
+                size = _size * 2;
+            }
+            else
+            {
+                autoBuffer = renderer.BufferManager.GetBuffer(_handle, false, out int bufferSize);
+
+                if (_offset >= bufferSize)
+                {
+                    autoBuffer = null;
+                }
+
+                type = _type.Convert();
+                offset = _offset;
+                size = _size;
+            }
+
+            if (autoBuffer != null)
+            {
+                DisposableBuffer buffer = autoBuffer.Get(cbs, offset, size);
+
+                return (buffer.Value, offset, type);
+            }
+
+            return (new MTLBuffer(IntPtr.Zero), 0, MTLIndexType.UInt16);
+        }
+    }
+}