switching from slicer to gcode viewer - unlocking lock file

src/PrusaSlicer.cpp

@@ -578,7 +578,7 @@ int CLI::run(int argc, char **argv)
         GUI::GUI_App *gui = new GUI::GUI_App();
 #endif // ENABLE_GCODE_VIEWER
 
-        if(!start_as_gcodeviewer) { // gcode viewer is currently not performing instance check
+        if(gui->get_app_mode() != GUI::GUI_App::EAppMode::GCodeViewer){ // gcode viewer is currently not performing instance check
 		    bool gui_single_instance_setting = gui->app_config->get("single_instance") == "1";
 		    if (Slic3r::instance_check(argc, argv, gui_single_instance_setting)) {
 			    //TODO: do we have delete gui and other stuff?

src/slic3r/GUI/GUI_App.cpp

@@ -1718,6 +1718,7 @@ void GUI_App::OSXStoreOpenFiles(const wxArrayString &fileNames)
         // Opening PrusaSlicer by drag & dropping a G-Code onto PrusaSlicer icon in Finder,
         // just G-codes were passed. Switch to G-code viewer mode.
         m_app_mode = EAppMode::GCodeViewer;
+        unlock_lockfile(get_instance_hash_string() + ".lock", data_dir() + "/cache/");
         if(app_config != nullptr)
             delete app_config;
         app_config = nullptr;

src/slic3r/GUI/InstanceCheck.cpp

@@ -264,6 +264,26 @@ bool instance_check(int argc, char** argv, bool app_config_single_instance)
 	return false;
 }
 
+#ifdef __APPLE__
+bool unlock_lockfile(const std::string& name, const std::string& path)
+{
+	std::string dest_dir = path + name;
+	//BOOST_LOG_TRIVIAL(debug) << "full lock path: " << dest_dir;
+	struct      flock fl;
+	int         fdlock;
+	fl.l_type = F_UNLCK;
+	fl.l_whence = SEEK_SET;
+	fl.l_start = 0;
+	fl.l_len = 1;
+	if ((fdlock = open(dest_dir.c_str(), O_WRONLY | O_CREAT, 0666)) == -1)
+		return false;
+
+	if (fcntl(fdlock, F_SETLK, &fl) == -1)
+		return false;
+
+	return true;
+}
+#endif //__APPLE__
 namespace GUI {
 
 wxDEFINE_EVENT(EVT_LOAD_MODEL_OTHER_INSTANCE, LoadFromOtherInstanceEvent);

src/slic3r/GUI/InstanceCheck.hpp

@@ -28,6 +28,8 @@ bool    instance_check(int argc, char** argv, bool app_config_single_instance);
 // apple implementation of inner functions of instance_check
 // in InstanceCheckMac.mm
 void    send_message_mac(const std::string& msg, const std::string& version);
+
+bool unlock_lockfile(const std::string& name, const std::string& path);
 #endif //__APPLE__
 
 namespace GUI {