GCodeProcessor -> Added cancel callback

src/libslic3r/GCode/GCodeProcessor.hpp

@@ -419,7 +419,8 @@ namespace Slic3r {
         Result&& extract_result() { return std::move(m_result); }
 
         // Process the gcode contained in the file with the given filename
-        void process_file(const std::string& filename);
+        // throws CanceledException through print->throw_if_canceled() (sent by the caller as callback).
+        void process_file(const std::string& filename, std::function<void()> cancel_callback = std::function<void()>());
 
         float get_time(PrintEstimatedTimeStatistics::ETimeMode mode) const;
         std::string get_time_dhm(PrintEstimatedTimeStatistics::ETimeMode mode) const;