From 6e4250287358561ddf47ef8facee04180a26b0d9 Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Thu, 10 Sep 2020 11:06:06 +0300
Subject: [PATCH] Support explicit padding in mesh vertices

---
 libs/gfx/include/psemek/gfx/mesh.hpp | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/libs/gfx/include/psemek/gfx/mesh.hpp b/libs/gfx/include/psemek/gfx/mesh.hpp
index 47522534..9bc167dc 100644
--- a/libs/gfx/include/psemek/gfx/mesh.hpp
+++ b/libs/gfx/include/psemek/gfx/mesh.hpp
@@ -19,9 +19,17 @@ namespace psemek::gfx
 	struct normalized
 	{};
 
+	// skips a single attribute index
 	struct skip
 	{};
 
+	// skips bytes in the vertex
+	template <std::size_t N>
+	struct padding
+	{
+		static constexpr std::size_t size = N;
+	};
+
 	template <typename Attrib>
 	struct attrib_traits;
 
@@ -148,6 +156,14 @@ namespace psemek::gfx
 	namespace detail
 	{
 
+		template <typename T>
+		struct is_padding : std::false_type
+		{};
+
+		template <std::size_t N>
+		struct is_padding<padding<N>> : std::true_type
+		{};
+
 		template <typename Attr>
 		std::size_t attr_size()
 		{
@@ -155,6 +171,10 @@ namespace psemek::gfx
 			{
 				return 0;
 			}
+			else if constexpr (is_padding<Attr>::value)
+			{
+				return Attr::size;
+			}
 			else
 			{
 				return sizeof(typename attrib_traits<Attr>::attrib_type);
@@ -192,6 +212,10 @@ namespace psemek::gfx
 				{
 					mesh_setup<Attribs...>::setup_impl(index + 1, offset, stride);
 				}
+				else if constexpr (is_padding<Attr1>::value)
+				{
+					mesh_setup<Attribs...>::setup_impl(index, offset + Attr1::size, stride);
+				}
 				else
 				{
 					using traits = attrib_traits<Attr1>;