[core] Use gl::Program to resolve some rough edges in the GL binding types

* Extract `ignore` util to separate header.
* `Segment` now tracks offset and length of indices, rather than primitives. This is more natural.
* Introduce `VertexVector` and `IndexVector` types. These types carry information about the intended draw mode (`Triangles`, `LineStrip`, etc.), and ensure that elements are always appended in a group size appropriate for that draw mode, for both indexed and unindexed rendering.
* `Program`, rather than `Drawable`, is now the unifying object for draw calls. `Program` is the best place to type check the draw call, because it is typed to carry information about the intended primitive, vertex type, attributes, and uniforms.
* Use the debug shaders for debug tile rendering, like gl-js.
* Fix the draw mode for background. It was drawing triangle strips with a triangles array. Surprised this didn’t cause issues. Now it’s type checked.

1 files changed, 7 insertions, 9 deletions

diff --git a/src/mbgl/gl/attribute.hpp b/src/mbgl/gl/attribute.hpp
index 126da38de5..a2b165fa21 100644
--- a/src/mbgl/gl/attribute.hpp
+++ b/src/mbgl/gl/attribute.hpp
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <mbgl/gl/types.hpp>
+#include <mbgl/util/ignore.hpp>
 
 #include <cstddef>
 #include <functional>
@@ -157,17 +158,14 @@ private:
     template <std::size_t... Is>
     static std::function<void (std::size_t)> binder(const State& state, std::index_sequence<Is...>) {
         return [&state] (std::size_t vertexOffset) {
-            noop((bindAttribute(std::get<Is>(state).location,
-                                std::get<Is>(state).count,
-                                std::get<Is>(state).type,
-                                sizeof(Vertex),
-                                vertexOffset,
-                                Vertex::attributeOffsets[Is]), 0)...);
+            ignore((bindAttribute(std::get<Is>(state).location,
+                                  std::get<Is>(state).count,
+                                  std::get<Is>(state).type,
+                                  sizeof(Vertex),
+                                  vertexOffset,
+                                  Vertex::attributeOffsets[Is]), 0)...);
         };
     }
-
-    // This exists only to provide a varags context for unpacking the assignments in `binder`.
-    template <int...> static void noop(int...) {}
 };
 
 } // namespace gl