Add StaticIndexBuffer

OpenRA.Game/Graphics/PlatformInterfaces.cs

@@ -84,6 +84,7 @@ namespace OpenRA
 	public interface IGraphicsContext : IDisposable
 	{
 		IVertexBuffer<Vertex> CreateVertexBuffer(int size);
+		IIndexBuffer CreateIndexBuffer(uint[] indices);
 		Vertex[] CreateVertices(int size);
 		ITexture CreateTexture();
 		IFrameBuffer CreateFrameBuffer(Size s);
@@ -114,6 +115,11 @@ namespace OpenRA
 		void SetData(T[] vertices, int offset, int start, int length);
 	}
 
+	public interface IIndexBuffer : IDisposable
+	{
+		void Bind();
+	}
+
 	public interface IShader
 	{
 		void SetBool(string name, bool value);

OpenRA.Game/Graphics/Util.cs

@@ -20,6 +20,16 @@ namespace OpenRA.Graphics
 		// yes, our channel order is nuts.
 		static readonly int[] ChannelMasks = { 2, 1, 0, 3 };
 
+		public static uint[] CreateQuadIndices(int quads)
+		{
+			var indices = new uint[quads * 6];
+			ReadOnlySpan<uint> cornerVertexMap = stackalloc uint[] { 0, 1, 2, 2, 3, 0 };
+			for (var i = 0; i < indices.Length; i++)
+				indices[i] = cornerVertexMap[i % 6] + (uint)(4 * (i / 6));
+
+			return indices;
+		}
+
 		public static void FastCreateQuad(Vertex[] vertices, in float3 o, Sprite r, int2 samplers, float paletteTextureIndex, int nv,
 			in float3 size, in float3 tint, float alpha, float rotation = 0f)
 		{

OpenRA.Platforms.Default/OpenGL.cs

@@ -131,6 +131,8 @@ namespace OpenRA.Platforms.Default
 		public const int GL_TEXTURE_MAX_LEVEL = 0x813D;
 
 		public const int GL_ARRAY_BUFFER = 0x8892;
+		public const int GL_ELEMENT_ARRAY_BUFFER = 0x8893;
+		public const int GL_STATIC_DRAW = 0x88E4;
 		public const int GL_DYNAMIC_DRAW = 0x88E8;
 
 		public const int GL_TEXTURE0 = 0x84C0;

OpenRA.Platforms.Default/Sdl2GraphicsContext.cs

@@ -68,6 +68,12 @@ namespace OpenRA.Platforms.Default
 			return new VertexBuffer<Vertex>(size);
 		}
 
+		public IIndexBuffer CreateIndexBuffer(uint[] indices)
+		{
+			VerifyThreadAffinity();
+			return new StaticIndexBuffer(indices);
+		}
+
 		public Vertex[] CreateVertices(int size)
 		{
 			VerifyThreadAffinity();

OpenRA.Platforms.Default/StaticIndexBuffer.cs

@@ -0,0 +1,62 @@
+#region Copyright & License Information
+/*
+ * Copyright (c) The OpenRA Developers and Contributors
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System;
+using System.Runtime.InteropServices;
+
+namespace OpenRA.Platforms.Default
+{
+	sealed class StaticIndexBuffer : ThreadAffine, IDisposable, IIndexBuffer
+	{
+		const int UintSize = 4;
+		uint buffer;
+		bool disposed;
+
+		public StaticIndexBuffer(uint[] indices)
+		{
+			OpenGL.glGenBuffers(1, out buffer);
+			OpenGL.CheckGLError();
+			Bind();
+
+			var ptr = GCHandle.Alloc(indices, GCHandleType.Pinned);
+			try
+			{
+				OpenGL.glBufferData(OpenGL.GL_ELEMENT_ARRAY_BUFFER,
+					new IntPtr(UintSize * indices.Length),
+					ptr.AddrOfPinnedObject(),
+					OpenGL.GL_STATIC_DRAW);
+			}
+			finally
+			{
+				ptr.Free();
+			}
+
+			OpenGL.CheckGLError();
+		}
+
+		public void Bind()
+		{
+			VerifyThreadAffinity();
+			OpenGL.glBindBuffer(OpenGL.GL_ELEMENT_ARRAY_BUFFER, buffer);
+			OpenGL.CheckGLError();
+		}
+
+		public void Dispose()
+		{
+			if (disposed)
+				return;
+
+			disposed = true;
+			OpenGL.glDeleteBuffers(1, ref buffer);
+			OpenGL.CheckGLError();
+		}
+	}
+}

OpenRA.Platforms.Default/ThreadedGraphicsContext.cs

@@ -46,6 +46,7 @@ namespace OpenRA.Platforms.Default
 		Func<object, IFrameBuffer> getCreateFrameBuffer;
 		Func<object, IShader> getCreateShader;
 		Func<object, IVertexBuffer<Vertex>> getCreateVertexBuffer;
+		Func<object, IIndexBuffer> getCreateIndexBuffer;
 		Action<object> doDrawPrimitives;
 		Action<object> doEnableScissor;
 		Action<object> doSetBlendMode;
@@ -94,6 +95,7 @@ namespace OpenRA.Platforms.Default
 						};
 					getCreateShader = name => new ThreadedShader(this, context.CreateShader((string)name));
 					getCreateVertexBuffer = length => new ThreadedVertexBuffer(this, context.CreateVertexBuffer((int)length));
+					getCreateIndexBuffer = indices => new ThreadedIndexBuffer(this, context.CreateIndexBuffer((uint[])indices));
 					doDrawPrimitives =
 						tuple =>
 						{
@@ -404,6 +406,11 @@ namespace OpenRA.Platforms.Default
 			return Send(getCreateVertexBuffer, length);
 		}
 
+		public IIndexBuffer CreateIndexBuffer(uint[] indices)
+		{
+			return Send(getCreateIndexBuffer, indices);
+		}
+
 		public Vertex[] CreateVertices(int size)
 		{
 			return GetVertices(size);
@@ -563,6 +570,30 @@ namespace OpenRA.Platforms.Default
 		}
 	}
 
+	sealed class ThreadedIndexBuffer : IIndexBuffer
+	{
+		readonly ThreadedGraphicsContext device;
+		readonly Action bind;
+		readonly Action dispose;
+
+		public ThreadedIndexBuffer(ThreadedGraphicsContext device, IIndexBuffer indexBuffer)
+		{
+			this.device = device;
+			bind = indexBuffer.Bind;
+			dispose = indexBuffer.Dispose;
+		}
+
+		public void Bind()
+		{
+			device.Post(bind);
+		}
+
+		public void Dispose()
+		{
+			device.Post(dispose);
+		}
+	}
+
 	sealed class ThreadedTexture : ITextureInternal
 	{
 		readonly ThreadedGraphicsContext device;