[core] Move OpenGL extension initialization to Backend

4 files changed, 23 insertions, 22 deletions

diff --git a/src/mbgl/gl/extension.cpp b/src/mbgl/gl/extension.cpp
index e6b4d9156e..41a5ea175e 100644
--- a/src/mbgl/gl/extension.cpp
+++ b/src/mbgl/gl/extension.cpp
@@ -1,7 +1,6 @@
 #include <mbgl/gl/extension.hpp>
 #include <mbgl/gl/gl.hpp>
 
-#include <mutex>
 #include <string>
 #include <vector>
 #include <cstring>
@@ -11,7 +10,7 @@ namespace gl {
 namespace detail {
 
 using Probes = std::vector<ExtensionFunctionBase::Probe>;
-using ExtensionFunctions = std::vector<std::pair<glProc*, Probes>>;
+using ExtensionFunctions = std::vector<std::pair<ProcAddress*, Probes>>;
 ExtensionFunctions& extensionFunctions() {
     static ExtensionFunctions functions;
     return functions;
@@ -23,22 +22,18 @@ ExtensionFunctionBase::ExtensionFunctionBase(std::initializer_list<Probe> probes
 
 } // namespace detail
 
-static std::once_flag initializeExtensionsOnce;
-
-void InitializeExtensions(glProc (*getProcAddress)(const char*)) {
-    std::call_once(initializeExtensionsOnce, [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;
-                    }
+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
diff --git a/src/mbgl/gl/extension.hpp b/src/mbgl/gl/extension.hpp
index ea5a1ae5f5..7d1d9a4d7d 100644
--- a/src/mbgl/gl/extension.hpp
+++ b/src/mbgl/gl/extension.hpp
@@ -2,12 +2,13 @@
 
 #include <initializer_list>
 #include <utility>
+#include <functional>
 
 namespace mbgl {
 namespace gl {
 
-using glProc = void (*)();
-void InitializeExtensions(glProc (*getProcAddress)(const char*));
+using ProcAddress = void (*)();
+void initializeExtensions(const std::function<ProcAddress(const char*)>&);
 
 namespace detail {
 
@@ -15,7 +16,7 @@ class ExtensionFunctionBase {
 public:
     using Probe = std::pair<const char*, const char*>;
     ExtensionFunctionBase(std::initializer_list<Probe>);
-    glProc ptr;
+    ProcAddress ptr;
 };
 
 } // namespace detail
diff --git a/src/mbgl/map/backend.cpp b/src/mbgl/map/backend.cpp
index a1a2f8f3a8..29f7522e4f 100644
--- a/src/mbgl/map/backend.cpp
+++ b/src/mbgl/map/backend.cpp
@@ -1,16 +1,23 @@
 #include <mbgl/map/backend.hpp>
 #include <mbgl/map/backend_scope.hpp>
 #include <mbgl/gl/context.hpp>
+#include <mbgl/gl/extension.hpp>
+#include <mbgl/gl/debugging.hpp>
 
 #include <cassert>
 
 namespace mbgl {
 
-Backend::Backend() : context(std::make_unique<gl::Context>()) {
-}
+Backend::Backend() = default;
 
 gl::Context& Backend::getContext() {
     assert(BackendScope::exists());
+    std::call_once(initialized, [this] {
+        context = std::make_unique<gl::Context>();
+        gl::debugging::enable();
+        gl::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 754959438b..73a084c8c6 100644
--- a/src/mbgl/renderer/painter.cpp
+++ b/src/mbgl/renderer/painter.cpp
@@ -94,8 +94,6 @@ Painter::Painter(gl::Context& context_,
     tileBorderSegments.emplace_back(0, 0, 4, 5);
     rasterSegments.emplace_back(0, 0, 4, 6);
 
-    gl::debugging::enable();
-
     programs = std::make_unique<Programs>(context,
                                           ProgramParameters{ pixelRatio, false, programCacheDir });
 #ifndef NDEBUG