[core] BackendScope prevent double (de-)activation

- Guards against duplicate activations by checking wether the backend of the prior scope is the same as the current ones
- Makes sure that only the most outer backend scope deactivates by tracking activation state

1 files changed, 4 insertions, 0 deletions

diff --git a/include/mbgl/map/backend_scope.hpp b/include/mbgl/map/backend_scope.hpp
index 4985cd197f..322c17b3fc 100644
--- a/include/mbgl/map/backend_scope.hpp
+++ b/include/mbgl/map/backend_scope.hpp
@@ -22,10 +22,14 @@ public:
     static bool exists();
 
 private:
+    void activate();
+    void deactivate();
+
     BackendScope* priorScope;
     BackendScope* nextScope;
     Backend& backend;
     const ScopeType scopeType;
+    bool activated = false;
 };
 
 } // namespace mbgl