[core] Restore support for GL implementations without VAO extension

3 files changed, 23 insertions, 10 deletions

diff --git a/src/mbgl/gl/context.cpp b/src/mbgl/gl/context.cpp
index a74e941bc6..5726eca5dc 100644
--- a/src/mbgl/gl/context.cpp
+++ b/src/mbgl/gl/context.cpp
@@ -123,12 +123,16 @@ UniqueTexture Context::createTexture() {
 }
 
 UniqueVertexArray Context::createVertexArray() {
-    if (!gl::GenVertexArrays) {
-        throw std::runtime_error("GL_ARB_vertex_array_object extension is required");
-    }
-
     VertexArrayID id = 0;
-    MBGL_CHECK_ERROR(gl::GenVertexArrays(1, &id));
+    if (gl::GenVertexArrays && !disableVAOExtension) {
+        MBGL_CHECK_ERROR(gl::GenVertexArrays(1, &id));
+    } else {
+        static bool reported = false;
+        if (!reported) {
+            Log::Warning(Event::OpenGL, "Not using Vertex Array Objects");
+            reported = true;
+        }
+    }
     return UniqueVertexArray(std::move(id), { this });
 }
 
diff --git a/src/mbgl/gl/context.hpp b/src/mbgl/gl/context.hpp
index 636dfc9eac..d1be794240 100644
--- a/src/mbgl/gl/context.hpp
+++ b/src/mbgl/gl/context.hpp
@@ -222,6 +222,10 @@ private:
     std::vector<VertexArrayID> abandonedVertexArrays;
     std::vector<FramebufferID> abandonedFramebuffers;
     std::vector<RenderbufferID> abandonedRenderbuffers;
+
+public:
+    // For testing
+    bool disableVAOExtension = false;
 };
 
 } // namespace gl
diff --git a/src/mbgl/gl/segment.hpp b/src/mbgl/gl/segment.hpp
index bb9f2f1ee8..7ce90e53a6 100644
--- a/src/mbgl/gl/segment.hpp
+++ b/src/mbgl/gl/segment.hpp
@@ -37,12 +37,17 @@ public:
             context.vertexBuffer.setDirty();
         }
 
-        context.vertexArrayObject = *vao;
-
-        if (indexBuffer != indexBuffer_) {
-            indexBuffer = indexBuffer_;
-            context.elementBuffer.setDirty();
+        if (*vao) {
+            context.vertexArrayObject = *vao;
+            if (indexBuffer != indexBuffer_) {
+                indexBuffer = indexBuffer_;
+                context.elementBuffer.setDirty();
+                context.elementBuffer = indexBuffer_;
+            }
+        } else {
+            // No VAO support. Force attributes to be rebound.
             context.elementBuffer = indexBuffer_;
+            variableBindings = {};
         }
 
         Attributes::bind(context,