[core] Refactor Buffer

1 files changed, 35 insertions, 3 deletions

diff --git a/include/mbgl/gl/gl.hpp b/include/mbgl/gl/gl.hpp
index a499d731d6..4468bf8c12 100644
--- a/include/mbgl/gl/gl.hpp
+++ b/include/mbgl/gl/gl.hpp
@@ -1,6 +1,10 @@
 #pragma once
 
+#include <mbgl/gl/types.hpp>
+
 #include <stdexcept>
+#include <type_traits>
+#include <limits>
 
 #if __APPLE__
     #include "TargetConditionals.h"
@@ -36,12 +40,40 @@ struct Error : std::runtime_error {
 
 void checkError(const char *cmd, const char *file, int line);
 
-} // namespace gl
-} // namespace mbgl
-
 #ifndef NDEBUG
 #define MBGL_CHECK_ERROR(cmd) ([&]() { struct __MBGL_C_E { ~__MBGL_C_E() { ::mbgl::gl::checkError(#cmd, __FILE__, __LINE__); } } __MBGL_C_E; return cmd; }())
 #else
 #define MBGL_CHECK_ERROR(cmd) (cmd)
 #endif
 
+template <typename T> struct AttributeType;
+
+template <> struct AttributeType<int8_t>   : std::integral_constant<GLenum, GL_BYTE> {};
+template <> struct AttributeType<uint8_t>  : std::integral_constant<GLenum, GL_UNSIGNED_BYTE> {};
+template <> struct AttributeType<int16_t>  : std::integral_constant<GLenum, GL_SHORT> {};
+template <> struct AttributeType<uint16_t> : std::integral_constant<GLenum, GL_UNSIGNED_SHORT> {};
+template <> struct AttributeType<int32_t>  : std::integral_constant<GLenum, GL_INT> {};
+template <> struct AttributeType<uint32_t> : std::integral_constant<GLenum, GL_UNSIGNED_INT> {};
+template <> struct AttributeType<float>    : std::integral_constant<GLenum, GL_FLOAT> {};
+
+template <std::size_t memberOffset, class V, class E, std::size_t N>
+void bindVertexAttribute(AttributeLocation location, const E (V::*)[N], const int8_t* offset) {
+    static_assert(std::is_standard_layout<V>::value, "vertex type must use standard layout");
+    static_assert(memberOffset % 4 == 0, "vertex attribute must be optimally aligned");
+    static_assert(1 <= N && N <= 4, "count must be 1, 2, 3, or 4");
+    static_assert(sizeof(V) <= std::numeric_limits<GLsizei>::max(), "vertex type is too big");
+    MBGL_CHECK_ERROR(glEnableVertexAttribArray(location));
+    MBGL_CHECK_ERROR(glVertexAttribPointer(location,
+                                           static_cast<GLint>(N),
+                                           AttributeType<E>::value,
+                                           false,
+                                           static_cast<GLsizei>(sizeof(V)),
+                                           offset + memberOffset));
+}
+
+// This has to be a macro because it uses the offsetof macro, which is the only legal way to get a member offset.
+#define MBGL_BIND_VERTEX_ATTRIBUTE(VertexType, member, offset) \
+    ::mbgl::gl::bindVertexAttribute<offsetof(VertexType, member)>(Shader::member, &VertexType::member, offset)
+
+} // namespace gl
+} // namespace mbgl