[core] Return to static, per-segment approach to VAOs

This is safer now -- it can be an implementation detail of Segment/Context. And the typing of SegmentVector now ensures that the attributes and program match.

3 files changed, 10 insertions, 42 deletions

diff --git a/src/mbgl/gl/context.cpp b/src/mbgl/gl/context.cpp
index 3251be0c87..41e81a186f 100644
--- a/src/mbgl/gl/context.cpp
+++ b/src/mbgl/gl/context.cpp
@@ -6,7 +6,7 @@
 #include <mbgl/util/std.hpp>
 #include <mbgl/platform/log.hpp>
 
-#include <boost/functional/hash.hpp>
+#include <cstring>
 
 namespace mbgl {
 namespace gl {
@@ -434,15 +434,6 @@ PrimitiveType Context::operator()(const TriangleStrip&) {
     return PrimitiveType::TriangleStrip;
 }
 
-std::size_t Context::VertexArrayObjectHash::operator()(const VertexArrayObjectKey& key) const {
-    std::size_t seed = 0;
-    boost::hash_combine(seed, std::get<0>(key));
-    boost::hash_combine(seed, std::get<1>(key));
-    boost::hash_combine(seed, std::get<2>(key));
-    boost::hash_combine(seed, std::get<3>(key));
-    return seed;
-}
-
 void Context::setDepthMode(const DepthMode& depth) {
     if (depth.func == DepthMode::Always && !depth.mask) {
         depthTest = false;
@@ -503,23 +494,15 @@ void Context::draw(const Drawable& drawable) {
                 return true;
             }
 
-            VertexArrayObjectKey vaoKey {
-                drawable.program,
-                drawable.vertexBuffer,
-                drawable.indexBuffer,
-                segment.vertexOffset
-            };
-
-            auto it = vaos.find(vaoKey);
-            if (it != vaos.end()) {
-                vertexArrayObject = it->second;
+            if (segment.vao) {
+                vertexArrayObject = *segment.vao;
                 return false;
             }
 
             VertexArrayID id = 0;
             MBGL_CHECK_ERROR(gl::GenVertexArrays(1, &id));
             vertexArrayObject = id;
-            vaos.emplace(vaoKey, UniqueVertexArray(std::move(id), { this }));
+            segment.vao = UniqueVertexArray(std::move(id), { this });
 
             // If we are initializing a new VAO, we need to force the buffers
             // to be rebound. VAOs don't inherit the existing buffer bindings.
@@ -555,9 +538,6 @@ void Context::performCleanup() {
         if (program == id) {
             program.setDirty();
         }
-        mbgl::util::erase_if(vaos, [&] (const VertexArrayObjectMap::value_type& kv) {
-            return std::get<0>(kv.first) == id;
-        });
         MBGL_CHECK_ERROR(glDeleteProgram(id));
     }
     abandonedPrograms.clear();
@@ -574,10 +554,6 @@ void Context::performCleanup() {
             } else if (elementBuffer == id) {
                 elementBuffer.setDirty();
             }
-            mbgl::util::erase_if(vaos, [&] (const VertexArrayObjectMap::value_type& kv) {
-                return std::get<1>(kv.first) == id
-                    || std::get<2>(kv.first) == id;
-            });
         }
         MBGL_CHECK_ERROR(glDeleteBuffers(int(abandonedBuffers.size()), abandonedBuffers.data()));
         abandonedBuffers.clear();
diff --git a/src/mbgl/gl/context.hpp b/src/mbgl/gl/context.hpp
index 33b7a555a8..093afa20ed 100644
--- a/src/mbgl/gl/context.hpp
+++ b/src/mbgl/gl/context.hpp
@@ -233,20 +233,6 @@ private:
     std::vector<VertexArrayID> abandonedVertexArrays;
     std::vector<FramebufferID> abandonedFramebuffers;
     std::vector<RenderbufferID> abandonedRenderbuffers;
-
-    using VertexArrayObjectKey = std::tuple<
-        ProgramID,  // Program
-        BufferID,   // Vertex buffer
-        BufferID,   // Index buffer
-        std::size_t // Vertex buffer offset
-    >;
-
-    struct VertexArrayObjectHash {
-        std::size_t operator()(const VertexArrayObjectKey&) const;
-    };
-
-    using VertexArrayObjectMap = std::unordered_map<VertexArrayObjectKey, UniqueVertexArray, VertexArrayObjectHash>;
-    VertexArrayObjectMap vaos;
 };
 
 } // namespace gl
diff --git a/src/mbgl/gl/segment.hpp b/src/mbgl/gl/segment.hpp
index 283b4f572a..0a735ababf 100644
--- a/src/mbgl/gl/segment.hpp
+++ b/src/mbgl/gl/segment.hpp
@@ -1,5 +1,7 @@
 #pragma once
 
+#include <mbgl/util/optional.hpp>
+
 #include <cstddef>
 
 namespace mbgl {
@@ -21,6 +23,10 @@ public:
 
     std::size_t vertexLength;
     std::size_t indexLength;
+
+private:
+    friend class Context;
+    mutable optional<UniqueVertexArray> vao;
 };
 
 template <class Attributes>