Fix rendering performance on macOS

src/libslic3r/Utils.hpp

@@ -2,6 +2,8 @@
 #define slic3r_Utils_hpp_
 
 #include <locale>
+#include <utility>
+#include <functional>
 #include <type_traits>
 
 #include "libslic3r.h"
@@ -148,6 +150,37 @@ template<class T> size_t next_highest_power_of_2(T v,
 
 extern std::string xml_escape(std::string text);
 
+
+class ScopeGuard
+{
+public:
+    typedef std::function<void()> Closure;
+private:
+    bool committed;
+    Closure closure;
+
+public:
+    ScopeGuard() {}
+    ScopeGuard(Closure closure) : closure(std::move(closure)) {}
+    ScopeGuard(const ScopeGuard&) = delete;
+    ScopeGuard(ScopeGuard &&other) : closure(std::move(other.closure)) {}
+
+    ~ScopeGuard()
+    {
+        if (closure) { closure(); }
+    }
+
+    ScopeGuard& operator=(const ScopeGuard&) = delete;
+    ScopeGuard& operator=(ScopeGuard &&other)
+    {
+        closure = std::move(other.closure);
+        return *this;
+    }
+
+    void reset() { closure = Closure(); }
+};
+
+
 } // namespace Slic3r
 
 #endif // slic3r_Utils_hpp_