From d807d5c74b4a26e427a0f0dcb421d880be1a0aff Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Sun, 4 Oct 2020 17:35:21 +0300
Subject: [PATCH] Refactor mesh setup & properly disable old attribs on
 re-setup

---
 libs/gfx/include/psemek/gfx/mesh.hpp | 118 +++++++++++++++------------
 1 file changed, 64 insertions(+), 54 deletions(-)

diff --git a/libs/gfx/include/psemek/gfx/mesh.hpp b/libs/gfx/include/psemek/gfx/mesh.hpp
index 7268116a..68ecb040 100644
--- a/libs/gfx/include/psemek/gfx/mesh.hpp
+++ b/libs/gfx/include/psemek/gfx/mesh.hpp
@@ -267,46 +267,50 @@ namespace psemek::gfx
 			}
 		};
 
-		template <bool IsInstanced, bool InstanceSetup, typename ... Attribs>
-		struct mesh_setup_base;
-
-		template <bool IsInstanced, bool InstanceSetup>
-		struct mesh_setup_base<IsInstanced, InstanceSetup>
+		struct mesh_setup_result
 		{
-			static std::size_t setup()
-			{
-				return 0;
-			}
-
-			static void setup_impl(int, std::size_t, std::size_t)
-			{}
+			std::size_t stride;
+			std::size_t max_index;
 		};
 
-		template <bool IsInstanced, bool InstanceSetup, typename Attr1, typename ... Attribs>
-		struct mesh_setup_base<IsInstanced, InstanceSetup, Attr1, Attribs...>
+		template <bool InstanceSetup, typename ... Attribs>
+		struct mesh_setup_base;
+
+		template <bool InstanceSetup>
+		struct mesh_setup_base<InstanceSetup>
 		{
-			static std::size_t setup()
+			static mesh_setup_result setup()
 			{
-				std::size_t const stride = stride_helper<InstanceSetup, Attr1, Attribs...>::stride();
-				setup_impl(0, 0, stride);
-				return stride;
+				return {0, 0};
 			}
 
-			static void setup_impl(int index, std::size_t offset, std::size_t stride)
+			static std::size_t setup_impl(std::size_t index, std::size_t, std::size_t)
+			{
+				return index;
+			}
+		};
+
+		template <bool InstanceSetup, typename Attr1, typename ... Attribs>
+		struct mesh_setup_base<InstanceSetup, Attr1, Attribs...>
+		{
+			static mesh_setup_result setup()
+			{
+				std::size_t const stride = stride_helper<InstanceSetup, Attr1, Attribs...>::stride();
+				auto const max_index = setup_impl(0, 0, stride);
+				return {stride, max_index};
+			}
+
+			static std::size_t setup_impl(std::size_t index, std::size_t offset, std::size_t stride)
 			{
 				if constexpr (std::is_same_v<Attr1, skip>)
 				{
-					mesh_setup_base<IsInstanced, InstanceSetup, Attribs...>::setup_impl(index + 1, offset, stride);
+					return mesh_setup_base<InstanceSetup, Attribs...>::setup_impl(index + 1, offset, stride);
 				}
 				else if constexpr (is_padding<Attr1>::value)
 				{
-					mesh_setup_base<IsInstanced, InstanceSetup, Attribs...>::setup_impl(index, offset + Attr1::size, stride);
+					return mesh_setup_base<InstanceSetup, Attribs...>::setup_impl(index, offset + Attr1::size, stride);
 				}
-				else if constexpr (!IsInstanced && is_instanced<Attr1>::value)
-				{
-					static_assert("cannot use instanced attribute for non-instanced mesh");
-				}
-				else if constexpr (!IsInstanced || (is_instanced<Attr1>::value == InstanceSetup))
+				else if constexpr (is_instanced<Attr1>::value == InstanceSetup)
 				{
 					using attr = typename remove_instanced<Attr1>::type;
 
@@ -324,7 +328,7 @@ namespace psemek::gfx
 								gl::VertexAttribDivisor(index + row, 1);
 						}
 
-						mesh_setup_base<IsInstanced, InstanceSetup, Attribs...>::setup_impl(index + attr::rows, offset + attr_size<Attr1>(), stride);
+						return mesh_setup_base<InstanceSetup, Attribs...>::setup_impl(index + attr::rows, offset + attr_size<Attr1>(), stride);
 					}
 					else
 					{
@@ -336,7 +340,7 @@ namespace psemek::gfx
 						gl::EnableVertexAttribArray(index);
 						gl::VertexAttribPointer(index, traits::size, traits::type, traits::normalized, stride, reinterpret_cast<char const *>(offset));
 
-						mesh_setup_base<IsInstanced, InstanceSetup, Attribs...>::setup_impl(index + 1, offset + attr_size<Attr1>(), stride);
+						return mesh_setup_base<InstanceSetup, Attribs...>::setup_impl(index + 1, offset + attr_size<Attr1>(), stride);
 					}
 				}
 				else
@@ -345,24 +349,39 @@ namespace psemek::gfx
 
 					if constexpr (is_matrix<attr>::value)
 					{
-						mesh_setup_base<IsInstanced, InstanceSetup, Attribs...>::setup_impl(index + attr::rows, offset, stride);
+						return mesh_setup_base<InstanceSetup, Attribs...>::setup_impl(index + attr::rows, offset, stride);
 					}
 					else
 					{
-						mesh_setup_base<IsInstanced, InstanceSetup, Attribs...>::setup_impl(index + 1, offset, stride);
+						return mesh_setup_base<InstanceSetup, Attribs...>::setup_impl(index + 1, offset, stride);
 					}
 				}
 			}
 		};
 
 		template <typename ... Attribs>
-		using mesh_setup = mesh_setup_base<false, false, Attribs...>;
+		using mesh_vertex_setup = mesh_setup_base<false, Attribs...>;
 
 		template <typename ... Attribs>
-		using instanced_mesh_vertex_setup = mesh_setup_base<true, false, Attribs...>;
+		using mesh_instance_setup = mesh_setup_base<true, Attribs...>;
 
-		template <typename ... Attribs>
-		using instanced_mesh_instance_setup = mesh_setup_base<true, true, Attribs...>;
+		template <typename ... Args>
+		struct has_instanced_attribs_impl
+			: std::false_type
+		{};
+
+		template <typename T, typename ... Args>
+		struct has_instanced_attribs_impl<T, Args...>
+			: has_instanced_attribs_impl<Args...>
+		{};
+
+		template <typename T, typename ... Args>
+		struct has_instanced_attribs_impl<instanced<T>, Args...>
+			: std::true_type
+		{};
+
+		template <typename ... Args>
+		constexpr bool has_instanced_attribs = has_instanced_attribs_impl<Args...>::value;
 
 		template <typename T>
 		struct gl_type;
@@ -433,24 +452,6 @@ namespace psemek::gfx
 				return std::nullopt;
 			}
 		}
-
-		template <typename ... Args>
-		struct has_instanced_attribs_impl
-			: std::false_type
-		{};
-
-		template <typename T, typename ... Args>
-		struct has_instanced_attribs_impl<T, Args...>
-			: has_instanced_attribs_impl<Args...>
-		{};
-
-		template <typename T, typename ... Args>
-		struct has_instanced_attribs_impl<instanced<T>, Args...>
-			: std::true_type
-		{};
-
-		template <typename ... Args>
-		constexpr bool has_instanced_attribs = has_instanced_attribs_impl<Args...>::value;
 	}
 
 	/* A generic mesh class
@@ -549,6 +550,8 @@ namespace psemek::gfx
 
 			GLenum primitive_type_;
 			GLenum index_type_;
+
+			std::size_t max_attribute_index_ = 0;
 		};
 
 		mesh_info info_;
@@ -559,16 +562,23 @@ namespace psemek::gfx
 	{
 		array_.bind();
 
+		for (std::size_t i = 0; i < info_.max_attribute_index_; ++i)
+			gl::DisableVertexAttribArray(i);
+
 		if (!vertex_buffer_) vertex_buffer_ = buffer{};
 		vertex_buffer_.bind();
-		info_.stride_ = detail::instanced_mesh_vertex_setup<Attribs...>::setup();
+		auto vertex_setup = detail::mesh_vertex_setup<Attribs...>::setup();
+		info_.stride_ = vertex_setup.stride;
+		info_.max_attribute_index_ = vertex_setup.max_index;
 
 		if constexpr (detail::has_instanced_attribs<Attribs...>)
 		{
 			if (!instance_buffer_) instance_buffer_ = buffer{};
 			instance_buffer_.bind();
-			info_.instance_stride_ = detail::instanced_mesh_instance_setup<Attribs...>::setup();
+			auto instance_setup = detail::mesh_instance_setup<Attribs...>::setup();
+			info_.instance_stride_ = instance_setup.stride;
 			info_.instanced_ = true;
+			info_.max_attribute_index_ = std::max(info_.max_attribute_index_, instance_setup.max_index);
 		}
 		else
 		{