ENH: add load_model_objects_and_custom_gcodes

Add cmd line option to pass layer change gcode.
This is useful for lithophane auto change colors.
Cmd: --custom-gcode custom_gcode_toolchange.json

Examples of the input json file can be found in the jira.

Jira: STUDIO-4070

Change-Id: I5beb5ff7d6d81028e95013e79f955e498cd3ba30
(cherry picked from commit bed6152b95c965ea87958d94ec069d8c883a8037)

src/libslic3r/Config.cpp

@@ -756,6 +756,7 @@ int ConfigBase::load_from_json(const std::string &file, ConfigSubstitutionContex
     try {
         boost::nowide::ifstream ifs(file);
         ifs >> j;
+        ifs.close();
 
         const ConfigDef* config_def = this->def();
         if (config_def == nullptr) {

src/libslic3r/CustomGCode.hpp

@@ -3,6 +3,7 @@
 
 #include <string>
 #include <vector>
+#include <nlohmann/json.hpp>
 
 namespace Slic3r {
 
@@ -43,6 +44,24 @@ struct Item
     std::string extra;      // this field is used for the extra data like :
                             // - G-code text for the Type::Custom 
                             // - message text for the Type::PausePrint
+    void from_json(const nlohmann::json& j) {
+        std::string type_str;
+        j.at("type").get_to(type_str);
+        std::map<std::string,Type> str2type = { {"ColorChange", ColorChange },
+            {"PausePrint",PausePrint},
+            {"ToolChange",ToolChange},
+            {"Template",Template},
+            {"Custom",Custom},
+            {"Unknown",Unknown} };
+        type = Unknown;
+        if (str2type.find(type_str) != str2type.end())
+            type = str2type[type_str];
+        j.at("print_z").get_to(print_z);
+        j.at("color").get_to(color);
+        j.at("extruder").get_to(extruder);
+        if(j.contains("extra"))
+            j.at("extra").get_to(extra);
+    }
 };
 
 enum Mode
@@ -71,6 +90,24 @@ struct Info
                 (rhs.gcodes == this->gcodes );
     }
     bool operator!=(const Info& rhs) const { return !(*this == rhs); }
+
+    void from_json(const nlohmann::json& j) {
+        std::string mode_str;
+        if (j.contains("mode"))
+            j.at("mode").get_to(mode_str);
+        if (mode_str == "SingleExtruder") mode = SingleExtruder;
+        else if (mode_str == "MultiAsSingle") mode = MultiAsSingle;
+        else if (mode_str == "MultiExtruder") mode = MultiExtruder;
+        else mode = Undef;
+
+        auto j_gcodes = j.at("gcodes");
+        gcodes.reserve(j_gcodes.size());
+        for (auto& jj : j_gcodes) {
+            Item item;
+            item.from_json(jj);
+            gcodes.push_back(item);
+        }
+    }
 };
 
 // If loaded configuration has a "colorprint_heights" option (if it was imported from older Slicer), 

src/libslic3r/PrintConfig.cpp

@@ -5247,6 +5247,12 @@ CLIMiscConfigDef::CLIMiscConfigDef()
     def->tooltip = L("Render with a software renderer. The bundled MESA software renderer is loaded instead of the default OpenGL driver.");
     def->min = 0;*/
 #endif /* _MSC_VER */
+
+    def = this->add("load_custom_gcodes", coString);
+    def->label = L("Load custom gcode");
+    def->tooltip = L("Load custom gcode from json");
+    def->cli_params = "custom_gcode_toolchange.json";
+    def->set_default_value(new ConfigOptionString());
 }
 
 const CLIActionsConfigDef    cli_actions_config_def;