From 21459ac4c92b82f2a3eeb1d9a6b462726001084c Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Tue, 18 Apr 2023 00:08:18 +0100
Subject: Specialize vertexAttribFunc for matrices because there's an upper
 limit of size 4 on attrib pointers

---
 gfx/gl/vertexArrayObject.hpp | 10 +++++-----
 lib/gl_traits.hpp            | 17 ++++++++++++++---
 2 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/gfx/gl/vertexArrayObject.hpp b/gfx/gl/vertexArrayObject.hpp
index 8c828c8..fdc43e9 100644
--- a/gfx/gl/vertexArrayObject.hpp
+++ b/gfx/gl/vertexArrayObject.hpp
@@ -72,19 +72,19 @@ public:
 
 private:
 	template<typename VertexT, typename T>
-	static void
+	static auto
 	set_pointer(const GLuint vertexArrayId, const void * ptr)
 	{
 		glEnableVertexAttribArray(vertexArrayId);
 		using traits = gl_traits<T>;
-		traits::vertexAttribFunc(vertexArrayId, traits::size, traits::type, sizeof(VertexT), ptr);
+		return traits::vertexAttribFunc(vertexArrayId, traits::size, traits::type, sizeof(VertexT), ptr);
 	}
 
 	template<typename VertexT, MP attrib>
-	static void
+	static auto
 	set_pointer(const GLuint vertexArrayId)
 	{
-		set_pointer<VertexT, typename decltype(attrib)::value_type>(vertexArrayId, attrib);
+		return set_pointer<VertexT, typename decltype(attrib)::value_type>(vertexArrayId, attrib);
 	}
 
 	template<typename VertexT, MP... attribs>
@@ -97,7 +97,7 @@ private:
 		}
 		else {
 			GLuint vertexArrayId {};
-			(set_pointer<VertexT, attribs>(vertexArrayId++), ...);
+			((vertexArrayId += set_pointer<VertexT, attribs>(vertexArrayId)), ...);
 		}
 	}
 };
diff --git a/lib/gl_traits.hpp b/lib/gl_traits.hpp
index e2e689d..10b42e5 100644
--- a/lib/gl_traits.hpp
+++ b/lib/gl_traits.hpp
@@ -11,20 +11,23 @@ struct gl_traits_base {
 };
 struct gl_traits_float : public gl_traits_base {
 	static constexpr auto vertexAttribFunc {
-			[](GLuint index, GLint size, GLenum type, GLsizei stride, const void * pointer) {
+			[](GLuint index, GLint size, GLenum type, GLsizei stride, const void * pointer) -> GLuint {
 				glVertexAttribPointer(index, size, type, GL_FALSE, stride, pointer);
+				return 1;
 			}};
 };
 struct gl_traits_longfloat : public gl_traits_base {
 	static constexpr auto vertexAttribFunc {
-			[](GLuint index, GLint size, GLenum type, GLsizei stride, const void * pointer) {
+			[](GLuint index, GLint size, GLenum type, GLsizei stride, const void * pointer) -> GLuint {
 				glVertexAttribLPointer(index, size, type, stride, pointer);
+				return 1;
 			}};
 };
 struct gl_traits_integer : public gl_traits_base {
 	static constexpr auto vertexAttribFunc {
-			[](GLuint index, GLint size, GLenum type, GLsizei stride, const void * pointer) {
+			[](GLuint index, GLint size, GLenum type, GLsizei stride, const void * pointer) -> GLuint {
 				glVertexAttribIPointer(index, size, type, stride, pointer);
+				return 1;
 			}};
 };
 template<> struct gl_traits<glm::f32> : public gl_traits_float {
@@ -63,4 +66,12 @@ template<glm::length_t L, typename T, glm::qualifier Q> struct gl_traits<glm::ve
 template<glm::length_t C, glm::length_t R, typename T, glm::qualifier Q>
 struct gl_traits<glm::mat<C, R, T, Q>> : public gl_traits<T> {
 	static constexpr GLint size {C * R};
+	static constexpr auto vertexAttribFunc {
+			[](GLuint index, GLint, GLenum type, GLsizei stride, const void * pointer) -> GLuint {
+				const auto m = static_cast<glm::mat<C, R, T, Q>>(pointer);
+				for (glm::length_t r = 0; r < R; r++) {
+					glVertexAttribPointer(index, C, type, GL_FALSE, stride, &m[r]);
+				}
+				return R;
+			}};
 };
-- 
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