23 files changed, 453 insertions, 379 deletions

diff --git a/cmake/core-files.cmake b/cmake/core-files.cmake
index e98f999116..8fc71bf280 100644
--- a/cmake/core-files.cmake
+++ b/cmake/core-files.cmake
@@ -58,10 +58,11 @@ set(MBGL_CORE_FILES
     src/mbgl/gl/context.hpp
     src/mbgl/gl/debugging.cpp
     src/mbgl/gl/debugging.hpp
+    src/mbgl/gl/debugging_extension.cpp
+    src/mbgl/gl/debugging_extension.hpp
     src/mbgl/gl/depth_mode.cpp
     src/mbgl/gl/depth_mode.hpp
     src/mbgl/gl/draw_mode.hpp
-    src/mbgl/gl/extension.cpp
     src/mbgl/gl/extension.hpp
     src/mbgl/gl/features.hpp
     src/mbgl/gl/framebuffer.hpp
@@ -71,8 +72,7 @@ set(MBGL_CORE_FILES
     src/mbgl/gl/object.hpp
     src/mbgl/gl/primitives.hpp
     src/mbgl/gl/program.hpp
-    src/mbgl/gl/program_binary.cpp
-    src/mbgl/gl/program_binary.hpp
+    src/mbgl/gl/program_binary_extension.hpp
     src/mbgl/gl/renderbuffer.hpp
     src/mbgl/gl/segment.cpp
     src/mbgl/gl/segment.hpp
@@ -85,8 +85,7 @@ set(MBGL_CORE_FILES
     src/mbgl/gl/uniform.hpp
     src/mbgl/gl/value.cpp
     src/mbgl/gl/value.hpp
-    src/mbgl/gl/vertex_array.cpp
-    src/mbgl/gl/vertex_array.hpp
+    src/mbgl/gl/vertex_array_extension.hpp
     src/mbgl/gl/vertex_buffer.hpp
 
     # layout
diff --git a/platform/glfw/glfw_view.cpp b/platform/glfw/glfw_view.cpp
index 812b0e32af..82f075fd6f 100644
--- a/platform/glfw/glfw_view.cpp
+++ b/platform/glfw/glfw_view.cpp
@@ -459,7 +459,7 @@ void GLFWView::run() {
         if (dirty) {
             const double started = glfwGetTime();
 
-            glfwMakeContextCurrent(window);
+            activate();
             mbgl::BackendScope scope { *this, mbgl::BackendScope::ScopeType::Implicit };
 
             updateViewBinding();
diff --git a/src/mbgl/gl/context.cpp b/src/mbgl/gl/context.cpp
index 97ebf687f9..75931dc9de 100644
--- a/src/mbgl/gl/context.cpp
+++ b/src/mbgl/gl/context.cpp
@@ -1,8 +1,9 @@
 #include <mbgl/map/view.hpp>
 #include <mbgl/gl/context.hpp>
 #include <mbgl/gl/gl.hpp>
-#include <mbgl/gl/vertex_array.hpp>
-#include <mbgl/gl/program_binary.hpp>
+#include <mbgl/gl/debugging_extension.hpp>
+#include <mbgl/gl/vertex_array_extension.hpp>
+#include <mbgl/gl/program_binary_extension.hpp>
 #include <mbgl/util/traits.hpp>
 #include <mbgl/util/std.hpp>
 #include <mbgl/util/logging.hpp>
@@ -37,10 +38,58 @@ static_assert(underlying_type(TextureFormat::Alpha) == GL_ALPHA, "OpenGL type mi
 
 static_assert(std::is_same<BinaryProgramFormat, GLenum>::value, "OpenGL type mismatch");
 
+Context::Context() = default;
+
 Context::~Context() {
     reset();
 }
 
+void Context::initializeExtensions(const std::function<gl::ProcAddress(const char*)>& getProcAddress) {
+    if (const char* extensions =
+            reinterpret_cast<const char*>(MBGL_CHECK_ERROR(glGetString(GL_EXTENSIONS)))) {
+
+        auto fn = [&](
+            std::initializer_list<std::pair<const char*, const char*>> probes) -> ProcAddress {
+            for (auto probe : probes) {
+                if (strstr(extensions, probe.first) != nullptr) {
+                    if (ProcAddress ptr = getProcAddress(probe.second)) {
+                        return ptr;
+                    }
+                }
+            }
+            return nullptr;
+        };
+
+        debugging = std::make_unique<extension::Debugging>(fn);
+        if (!disableVAOExtension) {
+            vertexArray = std::make_unique<extension::VertexArray>(fn);
+        }
+#if MBGL_HAS_BINARY_PROGRAMS
+        programBinary = std::make_unique<extension::ProgramBinary>(fn);
+#endif
+
+        if (!supportsVertexArrays()) {
+            Log::Warning(Event::OpenGL, "Not using Vertex Array Objects");
+        }
+    }
+}
+
+void Context::enableDebugging() {
+    if (!debugging || !debugging->debugMessageControl || !debugging->debugMessageCallback) {
+        return;
+    }
+
+    // This will enable all messages including performance hints
+    // MBGL_CHECK_ERROR(debugging->debugMessageControl(GL_DONT_CARE, GL_DONT_CARE, GL_DONT_CARE, 0, nullptr, GL_TRUE));
+
+    // This will only enable high and medium severity messages
+    MBGL_CHECK_ERROR(debugging->debugMessageControl(GL_DONT_CARE, GL_DONT_CARE, GL_DEBUG_SEVERITY_HIGH, 0, nullptr, GL_TRUE));
+    MBGL_CHECK_ERROR(debugging->debugMessageControl(GL_DONT_CARE, GL_DONT_CARE, GL_DEBUG_SEVERITY_MEDIUM, 0, nullptr, GL_TRUE));
+    MBGL_CHECK_ERROR(debugging->debugMessageControl(GL_DONT_CARE, GL_DONT_CARE, GL_DEBUG_SEVERITY_NOTIFICATION, 0, nullptr, GL_FALSE));
+
+    MBGL_CHECK_ERROR(debugging->debugMessageCallback(extension::Debugging::DebugCallback, nullptr));
+}
+
 UniqueShader Context::createShader(ShaderType type, const std::string& source) {
     UniqueShader result { MBGL_CHECK_ERROR(glCreateShader(static_cast<GLenum>(type))), { this } };
 
@@ -78,9 +127,11 @@ UniqueProgram Context::createProgram(ShaderID vertexShader, ShaderID fragmentSha
 #if MBGL_HAS_BINARY_PROGRAMS
 UniqueProgram Context::createProgram(BinaryProgramFormat binaryFormat,
                                      const std::string& binaryProgram) {
+    assert(supportsProgramBinaries());
     UniqueProgram result{ MBGL_CHECK_ERROR(glCreateProgram()), { this } };
-    MBGL_CHECK_ERROR(ProgramBinary(result, static_cast<GLenum>(binaryFormat), binaryProgram.data(),
-                                   static_cast<GLint>(binaryProgram.size())));
+    MBGL_CHECK_ERROR(programBinary->programBinary(result, static_cast<GLenum>(binaryFormat),
+                                                  binaryProgram.data(),
+                                                  static_cast<GLint>(binaryProgram.size())));
     verifyProgramLinkage(result);
     return result;
 }
@@ -144,15 +195,15 @@ UniqueTexture Context::createTexture() {
 }
 
 bool Context::supportsVertexArrays() const {
-    return gl::GenVertexArrays &&
-           gl::BindVertexArray &&
-           gl::DeleteVertexArrays &&
-           !disableVAOExtension;
+    return vertexArray &&
+           vertexArray->genVertexArrays &&
+           vertexArray->bindVertexArray &&
+           vertexArray->deleteVertexArrays;
 }
 
 #if MBGL_HAS_BINARY_PROGRAMS
 bool Context::supportsProgramBinaries() const {
-    return gl::ProgramBinary && gl::GetProgramBinary;
+    return programBinary && programBinary->programBinary && programBinary->getProgramBinary;
 }
 
 optional<std::pair<BinaryProgramFormat, std::string>>
@@ -165,8 +216,8 @@ Context::getBinaryProgram(ProgramID program_) const {
     std::string binary;
     binary.resize(binaryLength);
     GLenum binaryFormat;
-    MBGL_CHECK_ERROR(GetProgramBinary(program_, binaryLength, &binaryLength, &binaryFormat,
-                                      const_cast<char*>(binary.data())));
+    MBGL_CHECK_ERROR(programBinary->getProgramBinary(
+        program_, binaryLength, &binaryLength, &binaryFormat, const_cast<char*>(binary.data())));
     if (size_t(binaryLength) != binary.size()) {
         return {};
     }
@@ -181,7 +232,7 @@ optional<std::pair<BinaryProgramFormat, std::string>> Context::getBinaryProgram(
 UniqueVertexArray Context::createVertexArray() {
     assert(supportsVertexArrays());
     VertexArrayID id = 0;
-    MBGL_CHECK_ERROR(gl::GenVertexArrays(1, &id));
+    MBGL_CHECK_ERROR(vertexArray->genVertexArrays(1, &id));
     return UniqueVertexArray(std::move(id), { this });
 }
 
@@ -584,8 +635,8 @@ void Context::performCleanup() {
                 vertexArrayObject.setDirty();
             }
         }
-        MBGL_CHECK_ERROR(gl::DeleteVertexArrays(int(abandonedVertexArrays.size()),
-                                                abandonedVertexArrays.data()));
+        MBGL_CHECK_ERROR(vertexArray->deleteVertexArrays(int(abandonedVertexArrays.size()),
+                                                         abandonedVertexArrays.data()));
         abandonedVertexArrays.clear();
     }
 
diff --git a/src/mbgl/gl/context.hpp b/src/mbgl/gl/context.hpp
index 10ff4360d3..14af299baa 100644
--- a/src/mbgl/gl/context.hpp
+++ b/src/mbgl/gl/context.hpp
@@ -30,11 +30,23 @@ class View;
 namespace gl {
 
 constexpr size_t TextureMax = 64;
+using ProcAddress = void (*)();
+
+namespace extension {
+class VertexArray;
+class Debugging;
+class ProgramBinary;
+} // namespace extension
 
 class Context : private util::noncopyable {
 public:
+    Context();
     ~Context();
 
+    void initializeExtensions(const std::function<gl::ProcAddress(const char*)>&);
+
+    void enableDebugging();
+
     UniqueShader createShader(ShaderType type, const std::string& source);
     UniqueProgram createProgram(ShaderID vertexShader, ShaderID fragmentShader);
     UniqueProgram createProgram(BinaryProgramFormat binaryFormat, const std::string& binaryProgram);
@@ -164,11 +176,27 @@ public:
 
     void setDirtyState();
 
+    extension::Debugging* getDebuggingExtension() const {
+        return debugging.get();
+    }
+
+    extension::VertexArray* getVertexArrayExtension() const {
+        return vertexArray.get();
+    }
+
+private:
+    std::unique_ptr<extension::Debugging> debugging;
+    std::unique_ptr<extension::VertexArray> vertexArray;
+#if MBGL_HAS_BINARY_PROGRAMS
+    std::unique_ptr<extension::ProgramBinary> programBinary;
+#endif
+
+public:
     State<value::ActiveTexture> activeTexture;
     State<value::BindFramebuffer> bindFramebuffer;
     State<value::Viewport> viewport;
     std::array<State<value::BindTexture>, 2> texture;
-    State<value::BindVertexArray> vertexArrayObject;
+    State<value::BindVertexArray, const Context&> vertexArrayObject { *this };
     State<value::Program> program;
     State<value::BindVertexBuffer> vertexBuffer;
     State<value::BindElementBuffer> elementBuffer;
diff --git a/src/mbgl/gl/debugging.cpp b/src/mbgl/gl/debugging.cpp
index 5ce3e606ee..0d69d58be5 100644
--- a/src/mbgl/gl/debugging.cpp
+++ b/src/mbgl/gl/debugging.cpp
@@ -1,193 +1,33 @@
 #include <mbgl/gl/debugging.hpp>
-#include <mbgl/gl/gl.hpp>
-#include <mbgl/gl/extension.hpp>
-#include <mbgl/util/event.hpp>
-#include <mbgl/util/logging.hpp>
-
-#define GL_DEBUG_OUTPUT_SYNCHRONOUS       0x8242
-#define GL_DEBUG_NEXT_LOGGED_MESSAGE_LENGTH 0x8243
-#define GL_DEBUG_CALLBACK_FUNCTION        0x8244
-#define GL_DEBUG_CALLBACK_USER_PARAM      0x8245
-#define GL_DEBUG_SOURCE_API               0x8246
-#define GL_DEBUG_SOURCE_WINDOW_SYSTEM     0x8247
-#define GL_DEBUG_SOURCE_SHADER_COMPILER   0x8248
-#define GL_DEBUG_SOURCE_THIRD_PARTY       0x8249
-#define GL_DEBUG_SOURCE_APPLICATION       0x824A
-#define GL_DEBUG_SOURCE_OTHER             0x824B
-#define GL_DEBUG_TYPE_ERROR               0x824C
-#define GL_DEBUG_TYPE_DEPRECATED_BEHAVIOR 0x824D
-#define GL_DEBUG_TYPE_UNDEFINED_BEHAVIOR  0x824E
-#define GL_DEBUG_TYPE_PORTABILITY         0x824F
-#define GL_DEBUG_TYPE_PERFORMANCE         0x8250
-#define GL_DEBUG_TYPE_OTHER               0x8251
-#define GL_MAX_DEBUG_MESSAGE_LENGTH       0x9143
-#define GL_MAX_DEBUG_LOGGED_MESSAGES      0x9144
-#define GL_DEBUG_LOGGED_MESSAGES          0x9145
-#define GL_DEBUG_SEVERITY_HIGH            0x9146
-#define GL_DEBUG_SEVERITY_MEDIUM          0x9147
-#define GL_DEBUG_SEVERITY_LOW             0x9148
-#define GL_DEBUG_TYPE_MARKER              0x8268
-#define GL_DEBUG_TYPE_PUSH_GROUP          0x8269
-#define GL_DEBUG_TYPE_POP_GROUP           0x826A
-#define GL_DEBUG_SEVERITY_NOTIFICATION    0x826B
-#define GL_MAX_DEBUG_GROUP_STACK_DEPTH    0x826C
-#define GL_DEBUG_GROUP_STACK_DEPTH        0x826D
-#define GL_BUFFER                         0x82E0
-#define GL_SHADER                         0x82E1
-#define GL_PROGRAM                        0x82E2
-#define GL_QUERY                          0x82E3
-#define GL_PROGRAM_PIPELINE               0x82E4
-#define GL_SAMPLER                        0x82E6
-#define GL_MAX_LABEL_LENGTH               0x82E8
-#define GL_DEBUG_OUTPUT                   0x92E0
-#define GL_CONTEXT_FLAG_DEBUG_BIT         0x00000002
-#define GL_DISPLAY_LIST                   0x82E7
-#define GL_VERTEX_ARRAY                   0x8074
-#define GL_TRANSFORM_FEEDBACK             0x8E22
-#define GL_TEXTURE                        0x1702
-#define GL_RENDERBUFFER                   0x8D41
-#define GL_FRAMEBUFFER                    0x8D40
+#include <mbgl/gl/context.hpp>
+#include <mbgl/gl/debugging_extension.hpp>
 
 namespace mbgl {
 namespace gl {
-namespace debugging {
-
-typedef void (*GLDEBUGPROC)(GLenum source,
-                            GLenum type,
-                            GLuint id,
-                            GLenum severity,
-                            GLsizei length,
-                            const GLchar *message,
-                            const void *userParam);
-
-static ExtensionFunction<
-    void (GLenum source,
-          GLenum type,
-          GLenum severity,
-          GLsizei count,
-          const GLuint *ids,
-          GLboolean enabled)>
-    DebugMessageControl({
-        {"GL_KHR_debug",        "glDebugMessageControl"},
-        {"GL_ARB_debug_output", "glDebugMessageControlARB"}
-    });
-
-static ExtensionFunction<
-    void (GLDEBUGPROC callback,
-          const void *userParam)>
-    DebugMessageCallback({
-        {"GL_KHR_debug",        "glDebugMessageCallback"},
-        {"GL_ARB_debug_output", "glDebugMessageCallbackARB"}
-    });
-
-void debugCallback(GLenum source,
-                   GLenum type,
-                   GLuint id,
-                   GLenum severity,
-                   GLsizei /*length*/,
-                   const GLchar* message,
-                   const void* /*userParam*/)
-{
-    std::string strSource;
-    switch (source) {
-        case GL_DEBUG_SOURCE_API: strSource = "DEBUG_SOURCE_API"; break;
-        case GL_DEBUG_SOURCE_WINDOW_SYSTEM: strSource = "DEBUG_SOURCE_WINDOW_SYSTEM"; break;
-        case GL_DEBUG_SOURCE_SHADER_COMPILER: strSource = "DEBUG_SOURCE_SHADER_COMPILER"; break;
-        case GL_DEBUG_SOURCE_THIRD_PARTY: strSource = "DEBUG_SOURCE_THIRD_PARTY"; break;
-        case GL_DEBUG_SOURCE_APPLICATION: strSource = "DEBUG_SOURCE_APPLICATION"; break;
-        case GL_DEBUG_SOURCE_OTHER: strSource = "DEBUG_SOURCE_OTHER"; break;
-        default: strSource = "(unknown)"; break;
-    }
-
-    std::string strType;
-    switch (type) {
-        case GL_DEBUG_TYPE_ERROR: strType = "DEBUG_TYPE_ERROR"; break;
-        case GL_DEBUG_TYPE_DEPRECATED_BEHAVIOR: strType = "DEBUG_TYPE_DEPRECATED_BEHAVIOR"; break;
-        case GL_DEBUG_TYPE_UNDEFINED_BEHAVIOR: strType = "DEBUG_TYPE_UNDEFINED_BEHAVIOR"; break;
-        case GL_DEBUG_TYPE_PERFORMANCE: strType = "DEBUG_TYPE_PERFORMANCE"; break;
-        case GL_DEBUG_TYPE_PORTABILITY: strType = "DEBUG_TYPE_PORTABILITY"; break;
-        case GL_DEBUG_TYPE_OTHER: strType = "DEBUG_TYPE_OTHER"; break;
-        case GL_DEBUG_TYPE_MARKER: strType = "DEBUG_TYPE_MARKER"; break;
-        case GL_DEBUG_TYPE_PUSH_GROUP: strType = "DEBUG_TYPE_OTHER"; break;
-        case GL_DEBUG_TYPE_POP_GROUP: strType = "DEBUG_TYPE_POP_GROUP"; break;
-        default: strSource = "(unknown)"; break;
-    }
-
-    std::string strSeverity;
-    mbgl::EventSeverity evtSeverity;
-    switch (severity) {
-        case GL_DEBUG_SEVERITY_HIGH: strSeverity = "DEBUG_SEVERITY_HIGH"; evtSeverity = mbgl::EventSeverity::Error; break;
-        case GL_DEBUG_SEVERITY_MEDIUM: strSeverity = "DEBUG_SEVERITY_MEDIUM"; evtSeverity = mbgl::EventSeverity::Warning; break;
-        case GL_DEBUG_SEVERITY_LOW: strSeverity = "DEBUG_SEVERITY_LOW"; evtSeverity = mbgl::EventSeverity::Info; break;
-        case GL_DEBUG_SEVERITY_NOTIFICATION: strSeverity = "DEBUG_SEVERITY_NOTIFICATION"; evtSeverity = mbgl::EventSeverity::Debug; break;
-        default: strSource = "(unknown)"; evtSeverity = mbgl::EventSeverity::Debug; break;
-    }
-
-    mbgl::Log::Record(evtSeverity, mbgl::Event::OpenGL, "GL_%s GL_%s %u GL_%s - %s", strSource.c_str(), strType.c_str(), id, strSeverity.c_str(), message);
-}
-
-void enable() {
-    if (!DebugMessageControl || !DebugMessageCallback) {
-        return;
-    }
-
-    // This will enable all messages including performance hints
-    // MBGL_CHECK_ERROR(DebugMessageControl(GL_DONT_CARE, GL_DONT_CARE, GL_DONT_CARE, 0, nullptr, GL_TRUE));
-
-    // This will only enable high and medium severity messages
-    MBGL_CHECK_ERROR(DebugMessageControl(GL_DONT_CARE, GL_DONT_CARE, GL_DEBUG_SEVERITY_HIGH, 0, nullptr, GL_TRUE));
-    MBGL_CHECK_ERROR(DebugMessageControl(GL_DONT_CARE, GL_DONT_CARE, GL_DEBUG_SEVERITY_MEDIUM, 0, nullptr, GL_TRUE));
-    MBGL_CHECK_ERROR(DebugMessageControl(GL_DONT_CARE, GL_DONT_CARE, GL_DEBUG_SEVERITY_NOTIFICATION, 0, nullptr, GL_FALSE));
-
-    MBGL_CHECK_ERROR(DebugMessageCallback(debugCallback, nullptr));
-}
 
 #ifndef NDEBUG
-static ExtensionFunction<
-    void (GLenum source,
-          GLuint id,
-          GLsizei length,
-          const GLchar *message)>
-    PushDebugGroup({
-        {"GL_KHR_debug", "glPushDebugGroup"}
-    });
-
-static ExtensionFunction<
-    void ()>
-    PopDebugGroup({
-        {"GL_KHR_debug", "glPopDebugGroup"}
-    });
-
-static ExtensionFunction<
-    void (GLsizei length,
-          const GLchar *marker)>
-    PushGroupMarkerEXT({
-      {"GL_EXT_debug_marker", "glPushGroupMarkerEXT"}
-    });
 
-static ExtensionFunction<
-    void ()>
-    PopGroupMarkerEXT({
-      {"GL_EXT_debug_marker", "glPopGroupMarkerEXT"}
-    });
-
-group::group(const std::string& str) {
-    if (PushDebugGroup) {
-        PushDebugGroup(GL_DEBUG_SOURCE_APPLICATION, 0, GLsizei(str.size()), str.c_str());
-    } else if (PushGroupMarkerEXT) {
-        PushGroupMarkerEXT(GLsizei(str.size() + 1), str.c_str());
+DebugGroup::DebugGroup(const Context& context_, const std::string& name) : context(context_) {
+    if (auto debugging = context.getDebuggingExtension()) {
+        if (debugging->pushDebugGroup) {
+            debugging->pushDebugGroup(GL_DEBUG_SOURCE_APPLICATION, 0, GLsizei(name.size()), name.c_str());
+        } else if (debugging->pushGroupMarkerEXT) {
+            debugging->pushGroupMarkerEXT(GLsizei(name.size() + 1), name.c_str());
+        }
     }
 }
 
-group::~group() {
-    if (PopDebugGroup) {
-        PopDebugGroup();
-    } else if (PopGroupMarkerEXT) {
-        PopGroupMarkerEXT();
+DebugGroup::~DebugGroup() {
+    if (auto debugging = context.getDebuggingExtension()) {
+        if (debugging->popDebugGroup) {
+            debugging->popDebugGroup();
+        } else if (debugging->popGroupMarkerEXT) {
+            debugging->popGroupMarkerEXT();
+        }
     }
 }
+
 #endif
 
-} // namespace debugging
 } // namespace gl
 } // namespace mbgl
diff --git a/src/mbgl/gl/debugging.hpp b/src/mbgl/gl/debugging.hpp
index fe363701ad..d24b727295 100644
--- a/src/mbgl/gl/debugging.hpp
+++ b/src/mbgl/gl/debugging.hpp
@@ -1,26 +1,34 @@
 #pragma once
 
+#include <mbgl/util/noncopyable.hpp>
+
 #include <string>
 
 namespace mbgl {
 namespace gl {
-namespace debugging {
 
-void enable();
+class Context;
 
 #ifndef NDEBUG
-struct group {
-    group(const std::string&);
-    ~group();
+
+class DebugGroup : private util::noncopyable {
+public:
+    DebugGroup(const Context&, const std::string&);
+    ~DebugGroup();
+
+private:
+    const Context& context;
 };
 
 #define __MBGL_DEBUG_GROUP_NAME2(counter) __MBGL_DEBUG_GROUP_##counter
 #define __MBGL_DEBUG_GROUP_NAME(counter) __MBGL_DEBUG_GROUP_NAME2(counter)
-#define MBGL_DEBUG_GROUP(string) ::mbgl::gl::debugging::group __MBGL_DEBUG_GROUP_NAME(__LINE__)(string);
+#define MBGL_DEBUG_GROUP(context, name) const ::mbgl::gl::DebugGroup __MBGL_DEBUG_GROUP_NAME(__LINE__)(context, name);
+
 #else
-#define MBGL_DEBUG_GROUP(string)
+
+#define MBGL_DEBUG_GROUP(context, name)
+
 #endif
 
-} // namespace debugging
 } // namespace gl
 } // namespace mbgl
diff --git a/src/mbgl/gl/debugging_extension.cpp b/src/mbgl/gl/debugging_extension.cpp
new file mode 100644
index 0000000000..5afa4f50fc
--- /dev/null
+++ b/src/mbgl/gl/debugging_extension.cpp
@@ -0,0 +1,55 @@
+#include <mbgl/gl/debugging_extension.hpp>
+#include <mbgl/util/logging.hpp>
+
+namespace mbgl {
+namespace gl {
+namespace extension {
+
+void Debugging::DebugCallback(GLenum source,
+                              GLenum type,
+                              GLuint id,
+                              GLenum severity,
+                              GLsizei /* length */,
+                              const GLchar* message,
+                              const void* /* userParam */) {
+    std::string strSource;
+    switch (source) {
+        case GL_DEBUG_SOURCE_API: strSource = "DEBUG_SOURCE_API"; break;
+        case GL_DEBUG_SOURCE_WINDOW_SYSTEM: strSource = "DEBUG_SOURCE_WINDOW_SYSTEM"; break;
+        case GL_DEBUG_SOURCE_SHADER_COMPILER: strSource = "DEBUG_SOURCE_SHADER_COMPILER"; break;
+        case GL_DEBUG_SOURCE_THIRD_PARTY: strSource = "DEBUG_SOURCE_THIRD_PARTY"; break;
+        case GL_DEBUG_SOURCE_APPLICATION: strSource = "DEBUG_SOURCE_APPLICATION"; break;
+        case GL_DEBUG_SOURCE_OTHER: strSource = "DEBUG_SOURCE_OTHER"; break;
+        default: strSource = "(unknown)"; break;
+    }
+
+    std::string strType;
+    switch (type) {
+        case GL_DEBUG_TYPE_ERROR: strType = "DEBUG_TYPE_ERROR"; break;
+        case GL_DEBUG_TYPE_DEPRECATED_BEHAVIOR: strType = "DEBUG_TYPE_DEPRECATED_BEHAVIOR"; break;
+        case GL_DEBUG_TYPE_UNDEFINED_BEHAVIOR: strType = "DEBUG_TYPE_UNDEFINED_BEHAVIOR"; break;
+        case GL_DEBUG_TYPE_PERFORMANCE: strType = "DEBUG_TYPE_PERFORMANCE"; break;
+        case GL_DEBUG_TYPE_PORTABILITY: strType = "DEBUG_TYPE_PORTABILITY"; break;
+        case GL_DEBUG_TYPE_OTHER: strType = "DEBUG_TYPE_OTHER"; break;
+        case GL_DEBUG_TYPE_MARKER: strType = "DEBUG_TYPE_MARKER"; break;
+        case GL_DEBUG_TYPE_PUSH_GROUP: strType = "DEBUG_TYPE_OTHER"; break;
+        case GL_DEBUG_TYPE_POP_GROUP: strType = "DEBUG_TYPE_POP_GROUP"; break;
+        default: strSource = "(unknown)"; break;
+    }
+
+    std::string strSeverity;
+    mbgl::EventSeverity evtSeverity;
+    switch (severity) {
+        case GL_DEBUG_SEVERITY_HIGH: strSeverity = "DEBUG_SEVERITY_HIGH"; evtSeverity = mbgl::EventSeverity::Error; break;
+        case GL_DEBUG_SEVERITY_MEDIUM: strSeverity = "DEBUG_SEVERITY_MEDIUM"; evtSeverity = mbgl::EventSeverity::Warning; break;
+        case GL_DEBUG_SEVERITY_LOW: strSeverity = "DEBUG_SEVERITY_LOW"; evtSeverity = mbgl::EventSeverity::Info; break;
+        case GL_DEBUG_SEVERITY_NOTIFICATION: strSeverity = "DEBUG_SEVERITY_NOTIFICATION"; evtSeverity = mbgl::EventSeverity::Debug; break;
+        default: strSource = "(unknown)"; evtSeverity = mbgl::EventSeverity::Debug; break;
+    }
+
+    mbgl::Log::Record(evtSeverity, mbgl::Event::OpenGL, "GL_%s GL_%s %u GL_%s - %s", strSource.c_str(), strType.c_str(), id, strSeverity.c_str(), message);
+}
+
+} // namespace extension
+} // namespace gl
+} // namespace mbgl
diff --git a/src/mbgl/gl/debugging_extension.hpp b/src/mbgl/gl/debugging_extension.hpp
new file mode 100644
index 0000000000..c1835cfcdd
--- /dev/null
+++ b/src/mbgl/gl/debugging_extension.hpp
@@ -0,0 +1,120 @@
+#pragma once
+
+#include <mbgl/gl/extension.hpp>
+#include <mbgl/gl/gl.hpp>
+
+#define GL_DEBUG_OUTPUT_SYNCHRONOUS       0x8242
+#define GL_DEBUG_NEXT_LOGGED_MESSAGE_LENGTH 0x8243
+#define GL_DEBUG_CALLBACK_FUNCTION        0x8244
+#define GL_DEBUG_CALLBACK_USER_PARAM      0x8245
+#define GL_DEBUG_SOURCE_API               0x8246
+#define GL_DEBUG_SOURCE_WINDOW_SYSTEM     0x8247
+#define GL_DEBUG_SOURCE_SHADER_COMPILER   0x8248
+#define GL_DEBUG_SOURCE_THIRD_PARTY       0x8249
+#define GL_DEBUG_SOURCE_APPLICATION       0x824A
+#define GL_DEBUG_SOURCE_OTHER             0x824B
+#define GL_DEBUG_TYPE_ERROR               0x824C
+#define GL_DEBUG_TYPE_DEPRECATED_BEHAVIOR 0x824D
+#define GL_DEBUG_TYPE_UNDEFINED_BEHAVIOR  0x824E
+#define GL_DEBUG_TYPE_PORTABILITY         0x824F
+#define GL_DEBUG_TYPE_PERFORMANCE         0x8250
+#define GL_DEBUG_TYPE_OTHER               0x8251
+#define GL_MAX_DEBUG_MESSAGE_LENGTH       0x9143
+#define GL_MAX_DEBUG_LOGGED_MESSAGES      0x9144
+#define GL_DEBUG_LOGGED_MESSAGES          0x9145
+#define GL_DEBUG_SEVERITY_HIGH            0x9146
+#define GL_DEBUG_SEVERITY_MEDIUM          0x9147
+#define GL_DEBUG_SEVERITY_LOW             0x9148
+#define GL_DEBUG_TYPE_MARKER              0x8268
+#define GL_DEBUG_TYPE_PUSH_GROUP          0x8269
+#define GL_DEBUG_TYPE_POP_GROUP           0x826A
+#define GL_DEBUG_SEVERITY_NOTIFICATION    0x826B
+#define GL_MAX_DEBUG_GROUP_STACK_DEPTH    0x826C
+#define GL_DEBUG_GROUP_STACK_DEPTH        0x826D
+#define GL_BUFFER                         0x82E0
+#define GL_SHADER                         0x82E1
+#define GL_PROGRAM                        0x82E2
+#define GL_QUERY                          0x82E3
+#define GL_PROGRAM_PIPELINE               0x82E4
+#define GL_SAMPLER                        0x82E6
+#define GL_MAX_LABEL_LENGTH               0x82E8
+#define GL_DEBUG_OUTPUT                   0x92E0
+#define GL_CONTEXT_FLAG_DEBUG_BIT         0x00000002
+#define GL_DISPLAY_LIST                   0x82E7
+#define GL_VERTEX_ARRAY                   0x8074
+#define GL_TRANSFORM_FEEDBACK             0x8E22
+#define GL_TEXTURE                        0x1702
+#define GL_RENDERBUFFER                   0x8D41
+#define GL_FRAMEBUFFER                    0x8D40
+
+namespace mbgl {
+namespace gl {
+namespace extension {
+
+class Debugging {
+public:
+    typedef void (*Callback)(GLenum source,
+                             GLenum type,
+                             GLuint id,
+                             GLenum severity,
+                             GLsizei length,
+                             const GLchar* message,
+                             const void* userParam);
+
+    static void DebugCallback(GLenum source,
+                              GLenum type,
+                              GLuint id,
+                              GLenum severity,
+                              GLsizei /* length */,
+                              const GLchar* message,
+                              const void* /* userParam */);
+
+    template <typename Fn>
+    Debugging(const Fn& loadExtension)
+        :
+#ifndef NDEBUG
+          pushDebugGroup(
+              loadExtension({ { "GL_KHR_debug", "glPushDebugGroup" } })),
+          popDebugGroup(
+              loadExtension({ { "GL_KHR_debug", "glPopDebugGroup" } })),
+          pushGroupMarkerEXT(
+              loadExtension({ { "GL_EXT_debug_marker", "glPushGroupMarkerEXT" } })),
+          popGroupMarkerEXT(
+              loadExtension({ { "GL_EXT_debug_marker", "glPopGroupMarkerEXT" } })),
+#endif
+          debugMessageControl(
+              loadExtension({ { "GL_KHR_debug", "glDebugMessageControl" },
+                              { "GL_ARB_debug_output", "glDebugMessageControlARB" } })),
+          debugMessageCallback(
+              loadExtension({ { "GL_KHR_debug", "glDebugMessageCallback" },
+                              { "GL_ARB_debug_output", "glDebugMessageCallbackARB" } })) {
+    }
+
+#ifndef NDEBUG
+    const ExtensionFunction<void(GLenum source,
+                                 GLuint id,
+                                 GLsizei length,
+                                 const GLchar* message)> pushDebugGroup;
+
+    const ExtensionFunction<void()> popDebugGroup;
+
+    const ExtensionFunction<void(GLsizei length,
+                                 const GLchar* marker)> pushGroupMarkerEXT;
+
+    const ExtensionFunction<void()> popGroupMarkerEXT;
+#endif
+
+    const ExtensionFunction<void(GLenum source,
+                                 GLenum type,
+                                 GLenum severity,
+                                 GLsizei count,
+                                 const GLuint* ids,
+                                 GLboolean enabled)> debugMessageControl;
+
+    const ExtensionFunction<void(Callback callback,
+                                 const void* userParam)> debugMessageCallback;
+};
+
+} // namespace extension
+} // namespace gl
+} // namespace mbgl
diff --git a/src/mbgl/gl/extension.cpp b/src/mbgl/gl/extension.cpp
deleted file mode 100644
index 41a5ea175e..0000000000
--- a/src/mbgl/gl/extension.cpp
+++ /dev/null
@@ -1,40 +0,0 @@
-#include <mbgl/gl/extension.hpp>
-#include <mbgl/gl/gl.hpp>
-
-#include <string>
-#include <vector>
-#include <cstring>
-
-namespace mbgl {
-namespace gl {
-namespace detail {
-
-using Probes = std::vector<ExtensionFunctionBase::Probe>;
-using ExtensionFunctions = std::vector<std::pair<ProcAddress*, Probes>>;
-ExtensionFunctions& extensionFunctions() {
-    static ExtensionFunctions functions;
-    return functions;
-}
-
-ExtensionFunctionBase::ExtensionFunctionBase(std::initializer_list<Probe> probes) {
-    extensionFunctions().emplace_back(&ptr, probes);
-}
-
-} // namespace detail
-
-void initializeExtensions(const std::function<ProcAddress(const char*)>& getProcAddress) {
-    if (const char* extensions =
-            reinterpret_cast<const char*>(MBGL_CHECK_ERROR(glGetString(GL_EXTENSIONS)))) {
-        for (auto fn : detail::extensionFunctions()) {
-            for (auto probe : fn.second) {
-                if (strstr(extensions, probe.first) != nullptr) {
-                    *fn.first = getProcAddress(probe.second);
-                    break;
-                }
-            }
-        }
-    }
-}
-
-} // namespace gl
-} // namespace mbgl
diff --git a/src/mbgl/gl/extension.hpp b/src/mbgl/gl/extension.hpp
index 7d1d9a4d7d..8710314ef2 100644
--- a/src/mbgl/gl/extension.hpp
+++ b/src/mbgl/gl/extension.hpp
@@ -8,26 +8,15 @@ namespace mbgl {
 namespace gl {
 
 using ProcAddress = void (*)();
-void initializeExtensions(const std::function<ProcAddress(const char*)>&);
-
-namespace detail {
-
-class ExtensionFunctionBase {
-public:
-    using Probe = std::pair<const char*, const char*>;
-    ExtensionFunctionBase(std::initializer_list<Probe>);
-    ProcAddress ptr;
-};
-
-} // namespace detail
 
 template <class>
 class ExtensionFunction;
 
 template <class R, class... Args>
-class ExtensionFunction<R(Args...)> : protected detail::ExtensionFunctionBase {
+class ExtensionFunction<R(Args...)> {
 public:
-    using detail::ExtensionFunctionBase::ExtensionFunctionBase;
+    ExtensionFunction(const ProcAddress ptr_) : ptr(ptr_) {
+    }
 
     explicit operator bool() const {
         return ptr;
@@ -36,6 +25,9 @@ public:
     R operator()(Args... args) const {
         return (*reinterpret_cast<R (*)(Args...)>(ptr))(std::forward<Args>(args)...);
     }
+
+private:
+    const ProcAddress ptr;
 };
 
 } // namespace gl
diff --git a/src/mbgl/gl/program_binary.cpp b/src/mbgl/gl/program_binary.cpp
deleted file mode 100644
index ad147c819f..0000000000
--- a/src/mbgl/gl/program_binary.cpp
+++ /dev/null
@@ -1,24 +0,0 @@
-#include <mbgl/gl/program_binary.hpp>
-
-#if MBGL_HAS_BINARY_PROGRAMS
-
-namespace mbgl {
-namespace gl {
-
-ExtensionFunction<
-    void(GLuint program, GLsizei bufSize, GLsizei* length, GLenum* binaryFormat, GLvoid* binary)>
-    GetProgramBinary({
-        { "GL_OES_get_program_binary", "glGetProgramBinaryOES" },
-        { "GL_ARB_get_program_binary", "glGetProgramBinary" },
-    });
-
-ExtensionFunction<void(GLuint program, GLenum binaryFormat, const GLvoid* binary, GLint length)>
-    ProgramBinary({
-        { "GL_OES_get_program_binary", "glProgramBinaryOES" },
-        { "GL_ARB_get_program_binary", "glProgramBinary" },
-    });
-
-} // namespace gl
-} // namespace mbgl
-
-#endif
diff --git a/src/mbgl/gl/program_binary.hpp b/src/mbgl/gl/program_binary.hpp
deleted file mode 100644
index e888ed3d4a..0000000000
--- a/src/mbgl/gl/program_binary.hpp
+++ /dev/null
@@ -1,27 +0,0 @@
-#pragma once
-
-#include <mbgl/gl/features.hpp>
-#include <mbgl/gl/extension.hpp>
-#include <mbgl/gl/gl.hpp>
-
-#if MBGL_HAS_BINARY_PROGRAMS
-
-#define GL_PROGRAM_BINARY_LENGTH                   0x8741
-#define GL_NUM_PROGRAM_BINARY_FORMATS              0x87FE
-#define GL_PROGRAM_BINARY_FORMATS                  0x87FF
-
-namespace mbgl {
-namespace gl {
-
-extern ExtensionFunction<void(
-    GLuint program, GLsizei bufSize, GLsizei* length, GLenum* binaryFormat, GLvoid* binary)>
-    GetProgramBinary;
-
-extern ExtensionFunction<void(
-    GLuint program, GLenum binaryFormat, const GLvoid* binary, GLint length)>
-    ProgramBinary;
-
-} // namespace gl
-} // namespace mbgl
-
-#endif
diff --git a/src/mbgl/gl/program_binary_extension.hpp b/src/mbgl/gl/program_binary_extension.hpp
new file mode 100644
index 0000000000..a4aa1eeefc
--- /dev/null
+++ b/src/mbgl/gl/program_binary_extension.hpp
@@ -0,0 +1,44 @@
+#pragma once
+
+#include <mbgl/gl/features.hpp>
+#include <mbgl/gl/extension.hpp>
+#include <mbgl/gl/gl.hpp>
+
+#if MBGL_HAS_BINARY_PROGRAMS
+
+#define GL_PROGRAM_BINARY_LENGTH                   0x8741
+#define GL_NUM_PROGRAM_BINARY_FORMATS              0x87FE
+#define GL_PROGRAM_BINARY_FORMATS                  0x87FF
+
+namespace mbgl {
+namespace gl {
+namespace extension {
+
+class ProgramBinary {
+public:
+    template <typename Fn>
+    ProgramBinary(const Fn& loadExtension)
+        : getProgramBinary(loadExtension({
+              { "GL_OES_get_program_binary", "glGetProgramBinaryOES" },
+              { "GL_ARB_get_program_binary", "glGetProgramBinary" },
+          })),
+          programBinary(loadExtension({
+              { "GL_OES_get_program_binary", "glProgramBinaryOES" },
+              { "GL_ARB_get_program_binary", "glProgramBinary" },
+          })) {
+    }
+
+    const ExtensionFunction<void(
+        GLuint program, GLsizei bufSize, GLsizei* length, GLenum* binaryFormat, GLvoid* binary)>
+        getProgramBinary;
+
+    const ExtensionFunction<void(
+        GLuint program, GLenum binaryFormat, const GLvoid* binary, GLint length)>
+        programBinary;
+};
+
+} // namespace extension
+} // namespace gl
+} // namespace mbgl
+
+#endif
diff --git a/src/mbgl/gl/segment.hpp b/src/mbgl/gl/segment.hpp
index bd4926476f..45c81973f2 100644
--- a/src/mbgl/gl/segment.hpp
+++ b/src/mbgl/gl/segment.hpp
@@ -5,7 +5,6 @@
 #include <mbgl/util/optional.hpp>
 #include <mbgl/util/logging.hpp>
 
-#include <mutex>
 #include <cstddef>
 #include <vector>
 
@@ -47,10 +46,6 @@ public:
             }
         } else {
             // No VAO support. Force attributes to be rebound.
-            static std::once_flag reportedOnce;
-            std::call_once(reportedOnce, [] {
-                Log::Warning(Event::OpenGL, "Not using Vertex Array Objects");
-            });
             context.elementBuffer = indexBuffer_;
             variableBindings = {};
         }
diff --git a/src/mbgl/gl/state.hpp b/src/mbgl/gl/state.hpp
index efe869e5b9..f3268229d1 100644
--- a/src/mbgl/gl/state.hpp
+++ b/src/mbgl/gl/state.hpp
@@ -1,5 +1,7 @@
 #pragma once
 
+#include <tuple>
+
 namespace mbgl {
 namespace gl {
 
@@ -12,13 +14,16 @@ namespace gl {
 //     static void Set(const Type& value);
 //     static Type Get();
 // };
-template <typename T>
+template <typename T, typename... Args>
 class State {
 public:
+    State(Args&&... args) : params(std::forward_as_tuple(::std::forward<Args>(args)...)) {
+    }
+
     void operator=(const typename T::Type& value) {
         if (*this != value) {
             setCurrentValue(value);
-            T::Set(currentValue);
+            set(std::index_sequence_for<Args...>{});
         }
     }
 
@@ -50,22 +55,43 @@ public:
     }
 
 private:
+    template <std::size_t... I>
+    void set(std::index_sequence<I...>) {
+        T::Set(currentValue, std::get<I>(params)...);
+    }
+
+private:
     typename T::Type currentValue = T::Default;
     bool dirty = true;
+    const std::tuple<Args...> params;
 };
 
 // Helper struct that stores the current state and restores it upon destruction. You should not use
 // this code normally, except for debugging purposes.
-template <typename T>
+template <typename T, typename... Args>
 class PreserveState {
 public:
-    PreserveState() : value(T::Get()) {
+    PreserveState(Args&&... args)
+        : params(std::forward_as_tuple(std::forward<Args>(args)...)),
+          value(get(std::index_sequence_for<Args...>{})) {
     }
     ~PreserveState() {
-        T::Set(value);
+        set(std::index_sequence_for<Args...>{});
+    }
+
+private:
+    template <std::size_t... I>
+    typename T::Type get(std::index_sequence<I...>) {
+        return T::Get(std::get<I>(params)...);
+    }
+
+    template <std::size_t... I>
+    void set(std::index_sequence<I...>) {
+        T::Set(value, std::get<I>(params)...);
     }
 
 private:
+    const std::tuple<Args...> params;
     const typename T::Type value;
 };
 
diff --git a/src/mbgl/gl/value.cpp b/src/mbgl/gl/value.cpp
index 603d82dfd5..c081c941f5 100644
--- a/src/mbgl/gl/value.cpp
+++ b/src/mbgl/gl/value.cpp
@@ -1,6 +1,7 @@
 #include <mbgl/gl/value.hpp>
 #include <mbgl/gl/gl.hpp>
-#include <mbgl/gl/vertex_array.hpp>
+#include <mbgl/gl/context.hpp>
+#include <mbgl/gl/vertex_array_extension.hpp>
 
 namespace mbgl {
 namespace gl {
@@ -328,15 +329,17 @@ BindElementBuffer::Type BindElementBuffer::Get() {
 
 const constexpr BindVertexArray::Type BindVertexArray::Default;
 
-void BindVertexArray::Set(const Type& value) {
-    if (gl::BindVertexArray) {
-        MBGL_CHECK_ERROR(gl::BindVertexArray(value));
+void BindVertexArray::Set(const Type& value, const Context& context) {
+    if (auto vertexArray = context.getVertexArrayExtension()) {
+        if (vertexArray->bindVertexArray) {
+            MBGL_CHECK_ERROR(vertexArray->bindVertexArray(value));
+        }
     }
 }
 
-BindVertexArray::Type BindVertexArray::Get() {
+BindVertexArray::Type BindVertexArray::Get(const Context& context) {
     GLint binding = 0;
-    if (gl::BindVertexArray) {
+    if (context.getVertexArrayExtension()) {
 #ifdef GL_VERTEX_ARRAY_BINDING
         MBGL_CHECK_ERROR(glGetIntegerv(GL_VERTEX_ARRAY_BINDING, &binding));
 #elif GL_VERTEX_ARRAY_BINDING_OES
diff --git a/src/mbgl/gl/value.hpp b/src/mbgl/gl/value.hpp
index eccd3e7373..aa5cca6fec 100644
--- a/src/mbgl/gl/value.hpp
+++ b/src/mbgl/gl/value.hpp
@@ -10,6 +10,9 @@
 
 namespace mbgl {
 namespace gl {
+
+class Context;
+
 namespace value {
 
 struct ClearDepth {
@@ -225,8 +228,8 @@ struct BindElementBuffer {
 struct BindVertexArray {
     using Type = gl::VertexArrayID;
     static const constexpr Type Default = 0;
-    static void Set(const Type&);
-    static Type Get();
+    static void Set(const Type&, const Context&);
+    static Type Get(const Context&);
 };
 
 #if not MBGL_USE_GLES2
diff --git a/src/mbgl/gl/vertex_array.cpp b/src/mbgl/gl/vertex_array.cpp
deleted file mode 100644
index df63bbc4b7..0000000000
--- a/src/mbgl/gl/vertex_array.cpp
+++ /dev/null
@@ -1,22 +0,0 @@
-#include <mbgl/gl/vertex_array.hpp>
-
-namespace mbgl {
-namespace gl {
-
-ExtensionFunction<void(GLuint array)>
-    BindVertexArray({ { "GL_ARB_vertex_array_object", "glBindVertexArray" },
-                      { "GL_OES_vertex_array_object", "glBindVertexArrayOES" },
-                      { "GL_APPLE_vertex_array_object", "glBindVertexArrayAPPLE" } });
-
-ExtensionFunction<void(GLsizei n, const GLuint* arrays)>
-    DeleteVertexArrays({ { "GL_ARB_vertex_array_object", "glDeleteVertexArrays" },
-                         { "GL_OES_vertex_array_object", "glDeleteVertexArraysOES" },
-                         { "GL_APPLE_vertex_array_object", "glDeleteVertexArraysAPPLE" } });
-
-ExtensionFunction<void(GLsizei n, GLuint* arrays)>
-    GenVertexArrays({ { "GL_ARB_vertex_array_object", "glGenVertexArrays" },
-                      { "GL_OES_vertex_array_object", "glGenVertexArraysOES" },
-                      { "GL_APPLE_vertex_array_object", "glGenVertexArraysAPPLE" } });
-
-} // namespace gl
-} // namespace mbgl
diff --git a/src/mbgl/gl/vertex_array.hpp b/src/mbgl/gl/vertex_array.hpp
deleted file mode 100644
index 6b6e11324f..0000000000
--- a/src/mbgl/gl/vertex_array.hpp
+++ /dev/null
@@ -1,14 +0,0 @@
-#pragma once
-
-#include <mbgl/gl/extension.hpp>
-#include <mbgl/gl/gl.hpp>
-
-namespace mbgl {
-namespace gl {
-
-extern ExtensionFunction<void(GLuint array)> BindVertexArray;
-extern ExtensionFunction<void(GLsizei n, const GLuint* arrays)> DeleteVertexArrays;
-extern ExtensionFunction<void(GLsizei n, GLuint* arrays)> GenVertexArrays;
-
-} // namespace gl
-} // namespace mbgl
diff --git a/src/mbgl/gl/vertex_array_extension.hpp b/src/mbgl/gl/vertex_array_extension.hpp
new file mode 100644
index 0000000000..707a20e6f0
--- /dev/null
+++ b/src/mbgl/gl/vertex_array_extension.hpp
@@ -0,0 +1,37 @@
+#pragma once
+
+#include <mbgl/gl/extension.hpp>
+#include <mbgl/gl/gl.hpp>
+
+namespace mbgl {
+namespace gl {
+namespace extension {
+
+class VertexArray {
+public:
+    template <typename Fn>
+    VertexArray(const Fn& loadExtension)
+        : bindVertexArray(
+              loadExtension({ { "GL_ARB_vertex_array_object", "glBindVertexArray" },
+                              { "GL_OES_vertex_array_object", "glBindVertexArrayOES" },
+                              { "GL_APPLE_vertex_array_object", "glBindVertexArrayAPPLE" } })),
+          deleteVertexArrays(
+              loadExtension({ { "GL_ARB_vertex_array_object", "glDeleteVertexArrays" },
+                              { "GL_OES_vertex_array_object", "glDeleteVertexArraysOES" },
+                              { "GL_APPLE_vertex_array_object", "glDeleteVertexArraysAPPLE" } })),
+          genVertexArrays(
+              loadExtension({ { "GL_ARB_vertex_array_object", "glGenVertexArrays" },
+                              { "GL_OES_vertex_array_object", "glGenVertexArraysOES" },
+                              { "GL_APPLE_vertex_array_object", "glGenVertexArraysAPPLE" } })) {
+    }
+
+    const ExtensionFunction<void(GLuint array)> bindVertexArray;
+
+    const ExtensionFunction<void(GLsizei n, const GLuint* arrays)> deleteVertexArrays;
+
+    const ExtensionFunction<void(GLsizei n, GLuint* arrays)> genVertexArrays;
+};
+
+} // namespace extension
+} // namespace gl
+} // namespace mbgl
diff --git a/src/mbgl/map/backend.cpp b/src/mbgl/map/backend.cpp
index 29f7522e4f..c228719ba6 100644
--- a/src/mbgl/map/backend.cpp
+++ b/src/mbgl/map/backend.cpp
@@ -14,8 +14,8 @@ gl::Context& Backend::getContext() {
     assert(BackendScope::exists());
     std::call_once(initialized, [this] {
         context = std::make_unique<gl::Context>();
-        gl::debugging::enable();
-        gl::initializeExtensions(
+        context->enableDebugging();
+        context->initializeExtensions(
             std::bind(&Backend::initializeExtension, this, std::placeholders::_1));
     });
     return *context;
diff --git a/src/mbgl/renderer/painter.cpp b/src/mbgl/renderer/painter.cpp
index 73a084c8c6..f7a498ecae 100644
--- a/src/mbgl/renderer/painter.cpp
+++ b/src/mbgl/renderer/painter.cpp
@@ -150,7 +150,7 @@ void Painter::render(const Style& style, const FrameData& frame_, View& view, Sp
     // - UPLOAD PASS -------------------------------------------------------------------------------
     // Uploads all required buffers and images before we do any actual rendering.
     {
-        MBGL_DEBUG_GROUP("upload");
+        MBGL_DEBUG_GROUP(context, "upload");
 
         spriteAtlas->upload(context, 0);
 
@@ -170,7 +170,7 @@ void Painter::render(const Style& style, const FrameData& frame_, View& view, Sp
     // Renders the backdrop of the OpenGL view. This also paints in areas where we don't have any
     // tiles whatsoever.
     {
-        MBGL_DEBUG_GROUP("clear");
+        MBGL_DEBUG_GROUP(context, "clear");
         view.bind();
         context.clear(paintMode() == PaintMode::Overdraw
                         ? Color::black()
@@ -182,7 +182,7 @@ void Painter::render(const Style& style, const FrameData& frame_, View& view, Sp
     // - CLIPPING MASKS ----------------------------------------------------------------------------
     // Draws the clipping masks to the stencil buffer.
     {
-        MBGL_DEBUG_GROUP("clip");
+        MBGL_DEBUG_GROUP(context, "clip");
 
         // Update all clipping IDs.
         algorithm::ClipIDGenerator generator;
@@ -190,10 +190,10 @@ void Painter::render(const Style& style, const FrameData& frame_, View& view, Sp
             source->baseImpl->startRender(generator, projMatrix, state);
         }
 
-        MBGL_DEBUG_GROUP("clipping masks");
+        MBGL_DEBUG_GROUP(context, "clipping masks");
 
         for (const auto& stencil : generator.getStencils()) {
-            MBGL_DEBUG_GROUP(std::string{ "mask: " } + util::toString(stencil.first));
+            MBGL_DEBUG_GROUP(context, std::string{ "mask: " } + util::toString(stencil.first));
             renderClippingMask(stencil.first, stencil.second);
         }
     }
@@ -230,7 +230,7 @@ void Painter::render(const Style& style, const FrameData& frame_, View& view, Sp
     // - DEBUG PASS --------------------------------------------------------------------------------
     // Renders debug overlays.
     {
-        MBGL_DEBUG_GROUP("debug");
+        MBGL_DEBUG_GROUP(context, "debug");
 
         // Finalize the rendering, e.g. by calling debug render calls per tile.
         // This guarantees that we have at least one function per tile called.
@@ -250,7 +250,7 @@ void Painter::render(const Style& style, const FrameData& frame_, View& view, Sp
     // TODO: Find a better way to unbind VAOs after we're done with them without introducing
     // unnecessary bind(0)/bind(N) sequences.
     {
-        MBGL_DEBUG_GROUP("cleanup");
+        MBGL_DEBUG_GROUP(context, "cleanup");
 
         context.activeTexture = 1;
         context.texture[1] = 0;
@@ -268,7 +268,7 @@ void Painter::renderPass(PaintParameters& parameters,
                          uint32_t i, int8_t increment) {
     pass = pass_;
 
-    MBGL_DEBUG_GROUP(pass == RenderPass::Opaque ? "opaque" : "translucent");
+    MBGL_DEBUG_GROUP(context, pass == RenderPass::Opaque ? "opaque" : "translucent");
 
     if (debug::renderTree) {
         Log::Info(Event::Render, "%*s%s {", indent++ * 4, "",
@@ -285,10 +285,10 @@ void Painter::renderPass(PaintParameters& parameters,
             continue;
 
         if (layer.is<BackgroundLayer>()) {
-            MBGL_DEBUG_GROUP("background");
+            MBGL_DEBUG_GROUP(context, "background");
             renderBackground(parameters, *layer.as<BackgroundLayer>());
         } else if (layer.is<CustomLayer>()) {
-            MBGL_DEBUG_GROUP(layer.baseImpl->id + " - custom");
+            MBGL_DEBUG_GROUP(context, layer.baseImpl->id + " - custom");
 
             // Reset GL state to a known state so the CustomLayer always has a clean slate.
             context.vertexArrayObject = 0;
@@ -303,7 +303,7 @@ void Painter::renderPass(PaintParameters& parameters,
             parameters.view.bind();
             context.setDirtyState();
         } else {
-            MBGL_DEBUG_GROUP(layer.baseImpl->id + " - " + util::toString(item.tile->id));
+            MBGL_DEBUG_GROUP(context, layer.baseImpl->id + " - " + util::toString(item.tile->id));
             item.bucket->render(*this, parameters, layer, *item.tile);
         }
     }
diff --git a/src/mbgl/renderer/painter_debug.cpp b/src/mbgl/renderer/painter_debug.cpp
index 5b347884bf..37fa3bcb12 100644
--- a/src/mbgl/renderer/painter_debug.cpp
+++ b/src/mbgl/renderer/painter_debug.cpp
@@ -18,7 +18,7 @@ void Painter::renderTileDebug(const RenderTile& renderTile) {
     if (frame.debugOptions == MapDebugOptions::NoDebug)
         return;
 
-    MBGL_DEBUG_GROUP(std::string { "debug " } + util::toString(renderTile.id));
+    MBGL_DEBUG_GROUP(context, std::string { "debug " } + util::toString(renderTile.id));
 
     static const style::PaintProperties<>::Evaluated properties {};
     static const DebugProgram::PaintPropertyBinders paintAttibuteData(properties, 0);