From a1aa3594e75e611a69fbce1c6f9beef65d284533 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan.goodliffe@octal.co.uk>
Date: Fri, 6 Mar 2026 14:16:17 +0000
Subject: Extend glVertexArray with VertexArrayConfigurator

DSA version of VertexArrayObject.
---
 gfx/gl/glVertexArray.h | 114 ++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 112 insertions(+), 2 deletions(-)

(limited to 'gfx')

diff --git a/gfx/gl/glVertexArray.h b/gfx/gl/glVertexArray.h
index 891f21d..3594cbf 100644
--- a/gfx/gl/glVertexArray.h
+++ b/gfx/gl/glVertexArray.h
@@ -1,11 +1,121 @@
 #pragma once
 
-#include "config/types.h"
+#include "collections.h"
 #include "glArrays.h"
+#include "glBuffer.h"
+#include "gl_traits.h"
 
 namespace Impl {
+	class VertexArrayConfigurator {
+	public:
+		template<typename M, typename T> struct MP {
+			constexpr MP(M T::* ptr) : ptr {ptr} { }
+
+			operator GLuint() const
+			{
+				return static_cast<GLuint>(reinterpret_cast<const char *>(&(static_cast<T *>(nullptr)->*ptr))
+						- static_cast<const char *>(nullptr));
+			}
+
+			M T::* ptr;
+			using ValueType = M;
+		};
+
+		template<typename M, typename T> MP(M T::*) -> MP<M, T>;
+
+		explicit VertexArrayConfigurator(GLuint name) : name {name} { }
+
+		VertexArrayConfigurator &
+		addIndices(const glBuffer & buffer)
+		{
+			glVertexArrayElementBuffer(name, buffer);
+			return *this;
+		}
+
+		VertexArrayConfigurator &
+		addIndices(glBuffer & buffer, const SequentialCollection<GLuint> auto & indices)
+		{
+			buffer.storage(indices, 0);
+			return addIndices(buffer);
+		}
+
+		// Customisation point
+		template<typename VertexT> VertexArrayConfigurator & addAttribsFor(GLuint divisor, const glBuffer & buffer);
+
+		template<typename VertexT, MP... Attribs>
+		VertexArrayConfigurator &
+		addAttribs(const GLuint divisor)
+		{
+			configureAttribs<VertexT, Attribs...>(divisor);
+			return *this;
+		}
+
+		template<typename VertexT, MP... Attribs>
+		VertexArrayConfigurator &
+		addAttribs(const GLuint divisor, const glBuffer & buffer)
+		{
+			glVertexArrayVertexBuffer(name, binding, buffer, 0, sizeof(VertexT));
+			return addAttribs<VertexT, Attribs...>(divisor);
+		}
+
+		template<typename VertexT, MP... Attribs>
+		VertexArrayConfigurator &
+		addAttribs(const GLuint divisor, glBuffer & buffer, const SequentialCollection<VertexT> auto & data)
+		{
+			buffer.storage(data, 0);
+			return addAttribs<VertexT, Attribs...>(divisor, buffer);
+		}
+
+	private:
+		void
+		setPointerMeta(const GLuint usedAttribs)
+		{
+			while (attrib < usedAttribs) {
+				glEnableVertexArrayAttrib(name, attrib);
+				glVertexArrayAttribBinding(name, attrib++, binding);
+			}
+		}
+
+		template<typename T>
+		void
+		setPointer(const GLuint offset)
+		{
+			setPointerMeta(attrib + gl_traits<T>::vertexArrayAttribFormat(name, attrib, offset));
+		}
+
+		template<MP Attrib>
+		void
+		setPointer()
+		{
+			setPointer<typename decltype(Attrib)::ValueType>(Attrib);
+		}
+
+		template<typename VertexT, MP... Attribs>
+		void
+		configureAttribs(const GLuint divisor)
+		{
+			if constexpr (sizeof...(Attribs) == 0) {
+				setPointer<VertexT>(0);
+			}
+			else {
+				((setPointer<Attribs>()), ...);
+			}
+			glVertexArrayBindingDivisor(name, binding++, divisor);
+		}
+
+		GLuint name;
+		GLuint binding = 0;
+		GLuint attrib = 0;
+	};
+
 	// NOLINTNEXTLINE(readability-identifier-naming)
-	struct glVertexArray : Detail::glNamed { };
+	struct glVertexArray : Detail::glNamed {
+		VertexArrayConfigurator
+		configure()
+		{
+			return VertexArrayConfigurator {name};
+		}
+	};
 }
 
 // NOLINTBEGIN(readability-identifier-naming)
-- 
cgit v1.3