Fix of G-code Viewer not loading .gco files #5536

".gcode", ".gco", ".g" and ".ngc" were considered to be G-code file
extensions by the G-code import / export file dialogs, but not by
various other functions. Now the G-code extension is tested by
a single function is_gcode_file(string).

src/libslic3r/utils.cpp

@@ -522,6 +522,12 @@ bool is_idx_file(const boost::filesystem::directory_entry &dir_entry)
 	return is_plain_file(dir_entry) && strcasecmp(dir_entry.path().extension().string().c_str(), ".idx") == 0;
 }
 
+bool is_gcode_file(const std::string &path)
+{
+	return boost::iends_with(path, ".gcode") || boost::iends_with(path, ".gco") ||
+		   boost::iends_with(path, ".g")     || boost::iends_with(path, ".ngc");
+}
+
 } // namespace Slic3r
 
 #ifdef WIN32