feat: add model_name and plate_number placeholders

This uses the BBS project name from the `Project` tab which could be
susceptible to upstream changes removing this feature.

The project_name template only works when you open a 3MF file. If you
create a new project and set the project name `Model.model_info` is
always null whether you save the project or not. If you save the current
project, switch to a new project/different project, then re-load it then
the template works as expected.

The plate number is assumed to always be <100 which matches the
formatting of the plate number in the UI.

Relates-To: #3816

src/libslic3r/GCode.cpp

@@ -2399,6 +2399,8 @@ void GCode::_do_export(Print& print, GCodeOutputStream &file, ThumbnailsGenerato
         this->placeholder_parser().set("first_layer_temperature", new ConfigOptionInts(m_config.nozzle_temperature_initial_layer));
         this->placeholder_parser().set("max_print_height",new ConfigOptionInt(m_config.printable_height));
         this->placeholder_parser().set("z_offset", new ConfigOptionFloat(m_config.z_offset));
+        this->placeholder_parser().set("model_name", new ConfigOptionString(print.get_model_name()));
+        this->placeholder_parser().set("plate_number", new ConfigOptionString(print.get_plate_number_formatted()));
         this->placeholder_parser().set("plate_name", new ConfigOptionString(print.get_plate_name()));
         this->placeholder_parser().set("first_layer_height", new ConfigOptionFloat(m_config.initial_layer_print_height.value));
 

src/libslic3r/Print.cpp

@@ -2841,10 +2841,30 @@ std::string Print::output_filename(const std::string &filename_base) const
     DynamicConfig config = this->finished() ? this->print_statistics().config() : this->print_statistics().placeholders();
     config.set_key_value("num_filaments", new ConfigOptionInt((int)m_config.nozzle_diameter.size()));
     config.set_key_value("plate_name", new ConfigOptionString(get_plate_name()));
+    config.set_key_value("plate_number", new ConfigOptionString(get_plate_number_formatted()));
+    config.set_key_value("model_name", new ConfigOptionString(get_model_name()));
 
     return this->PrintBase::output_filename(m_config.filename_format.value, ".gcode", filename_base, &config);
 }
 
+std::string Print::get_model_name() const
+{
+    if (model().model_info != nullptr)
+    {
+        return model().model_info->model_name;
+    } else {
+        return "";
+    }
+}
+
+std::string Print::get_plate_number_formatted() const
+{
+    std::string plate_number = std::to_string(get_plate_index() + 1);
+    static const size_t n_zero = 2;
+
+    return std::string(n_zero - std::min(n_zero, plate_number.length()), '0') + plate_number;
+}
+
 //BBS: add gcode file preload logic
 void Print::set_gcode_file_ready()
 {

src/libslic3r/Print.hpp

@@ -903,6 +903,9 @@ class Print : public PrintBaseWithState<PrintStep, psCount>
 
 	std::string                 output_filename(const std::string &filename_base = std::string()) const override;
 
+	std::string                 get_model_name() const;
+	std::string                 get_plate_number_formatted() const;
+
     size_t                      num_print_regions() const throw() { return m_print_regions.size(); }
     const PrintRegion&          get_print_region(size_t idx) const  { return *m_print_regions[idx]; }
     const ToolOrdering&         get_tool_ordering() const { return m_wipe_tower_data.tool_ordering; }