Tech ENABLE_SAVE_COMMANDS_ALWAYS_ENABLED -> 1st installment: Allow to save/load empty projects

src/libslic3r/Format/3mf.cpp

@@ -2577,9 +2577,16 @@ namespace Slic3r {
 
     bool _3MF_Exporter::_add_build_to_model_stream(std::stringstream& stream, const BuildItemsList& build_items)
     {
+#if ENABLE_SAVE_COMMANDS_ALWAYS_ENABLED
+        // This happens for empty projects
+#endif // ENABLE_SAVE_COMMANDS_ALWAYS_ENABLED
         if (build_items.size() == 0) {
             add_error("No build item found");
+#if ENABLE_SAVE_COMMANDS_ALWAYS_ENABLED
+            return true;
+#else
             return false;
+#endif // ENABLE_SAVE_COMMANDS_ALWAYS_ENABLED
         }
 
         stream << " <" << BUILD_TAG << ">\n";

src/libslic3r/Model.cpp

@@ -161,8 +161,10 @@ Model Model::read_from_archive(const std::string& input_file, DynamicPrintConfig
     if (!result)
         throw Slic3r::RuntimeError("Loading of a model file failed.");
 
+#if !ENABLE_SAVE_COMMANDS_ALWAYS_ENABLED
     if (model.objects.empty())
         throw Slic3r::RuntimeError("The supplied file couldn't be read because it's empty");
+#endif // !ENABLE_SAVE_COMMANDS_ALWAYS_ENABLED
 
     for (ModelObject *o : model.objects)
     {

src/libslic3r/Technologies.hpp

@@ -49,6 +49,8 @@
 #define ENABLE_SINKING_CONTOURS (1 && ENABLE_2_4_0_ALPHA0)
 // Enable implementation of retract acceleration in gcode processor
 #define ENABLE_RETRACT_ACCELERATION (1 && ENABLE_2_4_0_ALPHA0)
+// Enable save and save as commands to be enabled also when the plater is empty and allow to load empty projects
+#define ENABLE_SAVE_COMMANDS_ALWAYS_ENABLED (1 && ENABLE_2_4_0_ALPHA0)
 
 
 #endif // _prusaslicer_technologies_h_

src/slic3r/GUI/GLCanvas3D.cpp

@@ -4108,13 +4108,24 @@ void GLCanvas3D::_render_thumbnail_internal(ThumbnailData& thumbnail_data, const
         }
     }
 
+#if !ENABLE_SAVE_COMMANDS_ALWAYS_ENABLED
     if (visible_volumes.empty())
         return;
+#endif // !ENABLE_SAVE_COMMANDS_ALWAYS_ENABLED
 
     BoundingBoxf3 volumes_box;
-    for (const GLVolume* vol : visible_volumes) {
+#if ENABLE_SAVE_COMMANDS_ALWAYS_ENABLED
-        volumes_box.merge(vol->transformed_bounding_box());
+    if (!visible_volumes.empty()) {
+#endif // ENABLE_SAVE_COMMANDS_ALWAYS_ENABLED
+        for (const GLVolume* vol : visible_volumes) {
+            volumes_box.merge(vol->transformed_bounding_box());
+        }
+#if ENABLE_SAVE_COMMANDS_ALWAYS_ENABLED
     }
+    else
+        // This happens for empty projects
+        volumes_box = wxGetApp().plater()->get_bed().get_bounding_box(true);
+#endif // ENABLE_SAVE_COMMANDS_ALWAYS_ENABLED
 
     Camera camera;
     camera.set_type(camera_type);

src/slic3r/GUI/MainFrame.cpp

@@ -824,15 +824,26 @@ bool MainFrame::can_start_new_project() const
 
 bool MainFrame::can_save() const
 {
+#if ENABLE_SAVE_COMMANDS_ALWAYS_ENABLED
+    return (m_plater != nullptr) &&
+        !m_plater->canvas3D()->get_gizmos_manager().is_in_editing_mode(false) &&
+        !m_plater->get_project_filename().empty() && m_plater->is_project_dirty();
+#else
     return (m_plater != nullptr) && !m_plater->model().objects.empty() &&
         !m_plater->canvas3D()->get_gizmos_manager().is_in_editing_mode(false) &&
         !m_plater->get_project_filename().empty() && m_plater->is_project_dirty();
+#endif // ENABLE_SAVE_COMMANDS_ALWAYS_ENABLED
 }
 
 bool MainFrame::can_save_as() const
 {
+#if ENABLE_SAVE_COMMANDS_ALWAYS_ENABLED
+    return (m_plater != nullptr) &&
+        !m_plater->canvas3D()->get_gizmos_manager().is_in_editing_mode(false);
+#else
     return (m_plater != nullptr) && !m_plater->model().objects.empty() &&
         !m_plater->canvas3D()->get_gizmos_manager().is_in_editing_mode(false);
+#endif // ENABLE_SAVE_COMMANDS_ALWAYS_ENABLED
 }
 
 void MainFrame::save_project()

src/slic3r/GUI/Plater.cpp

@@ -5587,8 +5587,16 @@ void Plater::export_amf()
 
 bool Plater::export_3mf(const boost::filesystem::path& output_path)
 {
+#if ENABLE_SAVE_COMMANDS_ALWAYS_ENABLED
+    if (p->model.objects.empty()) {
+        MessageDialog dialog(nullptr, _L("The plater is empty.\nConfirm you want to save the project ?"), _L("Save project"), wxYES_NO);
+        if (dialog.ShowModal() != wxID_YES)
+            return false;
+    }
+#else
     if (p->model.objects.empty())
         return false;
+#endif // ENABLE_SAVE_COMMANDS_ALWAYS_ENABLED
 
     wxString path;
     bool export_config = true;