[core] Improve attribute binding API

1 files changed, 50 insertions, 0 deletions

diff --git a/src/mbgl/gl/attribute.hpp b/src/mbgl/gl/attribute.hpp
new file mode 100644
index 0000000000..8bc474e967
--- /dev/null
+++ b/src/mbgl/gl/attribute.hpp
@@ -0,0 +1,50 @@
+#pragma once
+
+#include <mbgl/gl/types.hpp>
+#include <mbgl/gl/shader.hpp>
+
+#include <cstddef>
+#include <limits>
+#include <vector>
+
+namespace mbgl {
+namespace gl {
+
+template <typename T, std::size_t N>
+class Attribute {
+public:
+    Attribute(const char* name, const Shader& shader)
+        : location(shader.getAttributeLocation(name)) {}
+
+    AttributeLocation location;
+};
+
+class AttributeBinding {
+public:
+    template <class Vertex, class T, std::size_t N, std::size_t O>
+    AttributeBinding(const T (Vertex::*)[N], const Attribute<T, N>& attribute, std::integral_constant<std::size_t, O>)
+        : location(attribute.location),
+          type(DataTypeOf<T>::value),
+          count(N),
+          offset(O) {
+        static_assert(std::is_standard_layout<Vertex>::value, "vertex type must use standard layout");
+        static_assert(O % 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(Vertex) <= std::numeric_limits<int32_t>::max(), "vertex type is too big");
+    }
+
+    AttributeLocation location;
+    DataType type;
+    uint8_t count;
+    std::size_t offset;
+};
+
+#define MBGL_MAKE_ATTRIBUTE_BINDING(Vertex, shader, name) \
+    ::mbgl::gl::AttributeBinding(&Vertex::name, \
+                                 shader.name, \
+                                 std::integral_constant<std::size_t, offsetof(Vertex, name)>())
+
+template <class Shader, class Vertex> struct AttributeBindings;
+
+} // namespace gl
+} // namespace mbgl