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source/opengl/data_managers/mesh_vertex_buffer_manager.cpp

@@ -0,0 +1,133 @@
+#include "opengl/data_managers/mesh_vertex_buffer_manager.hpp"
+
+void zgl::mesh_vertex_buffer_manager::process(store_type& store)
+{
+	for (const auto& [ id, mesh ] : store)
+	{
+		// The ireator must reutrn a pair containing the components and a tuple of spans
+	}
+}
+
+template<typename C, typename... Ts>
+void dynamic_vertex_buffer<C, Ts...>::build_vertex_buffer(
+	std::vector<ztu::u8>& vertex_buffer,
+	std::size_t& component_count,
+	std::array<GLenum, sizeof...(Ts)>& component_types,
+	std::array<GLint, sizeof...(Ts)>& component_lengths,
+	GLsizei& stride
+) const {
+	const auto for_all_components = [&]<typename T>(auto&& f, const T default_value)
+	{
+		return std::apply(
+			[&](const auto&... component_buffer)
+			{
+				std::array<T, sizeof...(component_buffer)> results{};
+				auto i = std::size_t{};
+				(
+					(
+						results[i] = [&](const auto& buffer, const auto index) -> T
+						{
+							if ((m_components & C{ 1 << index }) != C{})
+							{
+								return f(buffer, index);
+							}
+							return default_value;
+						}(component_buffer, i),
+						++i
+					),
+					...
+				);
+				return results;
+			},
+			m_component_buffers
+		);
+	};
+
+	component_count = 0;
+	component_types = for_all_components(
+		ztu::specialised_lambda
+		{
+			[&component_count]<numeric_type Component, std::size_t Count>(const std::vector<std::array<Component, Count>>&, std::size_t)
+			{
+				++component_count;
+				return zgl::type_utils::to_gl_type<Component>();
+			},
+			[&component_count]<numeric_type Component>(const std::vector<Component>&, std::size_t)
+			{
+				++component_count;
+				return zgl::type_utils::to_gl_type<Component>();
+			}
+		},
+		GLenum{ GL_INVALID_VALUE }
+	);
+
+	const auto element_counts = for_all_components(
+		[]<class Component>(const std::vector<Component>& buffer, std::size_t)
+		{
+			return buffer.size();
+		},
+		std::numeric_limits<std::size_t>::max()
+	);
+
+	const auto minimum_element_count = std::ranges::min(element_counts);
+
+	component_lengths = for_all_components(
+		ztu::specialised_lambda
+		{
+			[]<class Component>(const std::vector<Component>&, std::size_t)
+			{
+				return 1;
+			},
+			[]<class Component, std::size_t Count>(const std::vector<std::array<Component, Count>>&, std::size_t)
+			{
+				return Count;
+			}
+		},
+		GLsizei{ 0 }
+	);
+
+	auto component_sizes = std::array<GLsizei, sizeof...(Ts)>{};
+	for (std::size_t i{}; i != component_sizes.size(); ++i)
+	{
+		component_sizes[i] = component_lengths[i] * zgl::type_utils::size_of(component_types[i]);
+	}
+
+	const auto total_size = minimum_element_count * std::accumulate(
+		component_sizes.begin(),
+		component_sizes.end(),
+		GLsizei{ 0 }
+	);
+
+	vertex_buffer.resize(total_size);
+
+	// Calculate offsets and stride
+	auto component_offsets = component_sizes;
+	stride = 0;
+	for (std::size_t i{}; i != component_offsets.size(); ++i) {
+		component_offsets[i] = stride;
+		stride += component_sizes[i];
+	}
+
+	// Copy all the components over one by one
+	for_all_components(
+		[&]<class Component>(const std::vector<Component>& buffer, std::size_t index)
+		{
+			std::size_t pos = component_offsets[index];
+			for (std::size_t i{}; i != minimum_element_count; ++i)
+			{
+				std::memcpy(
+					&vertex_buffer[pos],
+					buffer[i].data(),
+					component_sizes[index]
+				);
+				pos += stride;
+			}
+			return 0;
+		},
+		0
+	);
+
+	// remove values of unused components
+	std::ignore = std::ranges::remove(component_lengths, 0);
+	std::ignore = std::ranges::remove(component_types, GL_INVALID_VALUE);
+}