From 07f478ba964464ff6a6f6bc6855acc8353b4594b Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Mon, 2 Jan 2023 15:10:27 +0000
Subject: Add helper for configuring vertex array objects/buffers of arbitrary
 things

---
 gfx/gl/vertexArrayObject.hpp | 76 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)
 create mode 100644 gfx/gl/vertexArrayObject.hpp

(limited to 'gfx/gl/vertexArrayObject.hpp')

diff --git a/gfx/gl/vertexArrayObject.hpp b/gfx/gl/vertexArrayObject.hpp
new file mode 100644
index 0000000..d90cc59
--- /dev/null
+++ b/gfx/gl/vertexArrayObject.hpp
@@ -0,0 +1,76 @@
+#pragma once
+
+#include "collections.hpp"
+#include "gl_traits.hpp"
+#include <GL/glew.h>
+#include <glm/common.hpp>
+
+template<typename Vertex> class VertexArrayObject {
+public:
+	template<auto Vertex::*... attribs>
+	static void
+	configure(const GLuint arrayObject, const GLuint arrayBuffer, const GLuint indexBuffer,
+			const SequentialCollection<Vertex> auto & vertices, const SequentialCollection<unsigned int> auto & indices)
+	{
+		glBindVertexArray(arrayObject);
+
+		configure_attribs<attribs...>(arrayBuffer);
+		data(vertices, arrayBuffer, GL_ARRAY_BUFFER);
+		data(indices, indexBuffer, GL_ELEMENT_ARRAY_BUFFER);
+
+		glBindVertexArray(0);
+	}
+
+	template<auto Vertex::*... attribs>
+	static void
+	configure(const GLuint arrayObject, const GLuint arrayBuffer, const SequentialCollection<Vertex> auto & vertices)
+	{
+		glBindVertexArray(arrayObject);
+
+		configure_attribs<attribs...>(arrayBuffer);
+		data(vertices, arrayBuffer, GL_ARRAY_BUFFER);
+
+		glBindVertexArray(0);
+	}
+
+	template<auto Vertex::*... attribs>
+	static void
+	configure(const GLuint arrayObject, const GLuint arrayBuffer)
+	{
+		glBindVertexArray(arrayObject);
+
+		configure_attribs<attribs...>(arrayBuffer);
+		glBufferData(GL_ARRAY_BUFFER, static_cast<GLsizeiptr>(sizeof(Vertex)), nullptr, GL_DYNAMIC_DRAW);
+
+		glBindVertexArray(0);
+	}
+
+private:
+	template<typename Data>
+	static void
+	data(const Data & data, const GLuint arrayBuffer, GLenum target)
+	{
+		using Value = typename Data::element_type;
+		glBindBuffer(target, arrayBuffer);
+		glBufferData(target, static_cast<GLsizeiptr>(sizeof(Value) * data.size()), data.data(), GL_STATIC_DRAW);
+	}
+
+	template<auto Vertex::*attrib>
+	static void
+	set_pointer(GLuint & vertexArrayId)
+	{
+		glEnableVertexAttribArray(vertexArrayId);
+		using traits = gl_traits<std::decay_t<decltype(std::declval<Vertex>().*attrib)>>;
+		glVertexAttribPointer(vertexArrayId++, traits::size, traits::type, GL_FALSE, sizeof(Vertex),
+				&(static_cast<const Vertex *>(nullptr)->*attrib));
+	}
+
+	template<auto Vertex::*... attribs>
+	static void
+	configure_attribs(const GLuint arrayBuffer)
+	{
+		glBindBuffer(GL_ARRAY_BUFFER, arrayBuffer);
+		GLuint vertexArrayId {};
+		(set_pointer<attribs>(vertexArrayId), ...);
+	}
+};
-- 
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