Copying from other config folders:

Find if there is more recent config in other folders (alpha / beta / release).
If yes, ask user, make snapshot, copy files.
if there is no current config, ask user and copy recent one.

src/libslic3r/AppConfig.cpp

@@ -248,11 +248,11 @@ std::string AppConfig::load()
     bool                    recovered = false;
 
     try {
-        ifs.open(AppConfig::config_path());
+        ifs.open(AppConfig::loading_path());
 #ifdef WIN32
         // Verify the checksum of the config file without taking just for debugging purpose.
         if (!verify_config_file_checksum(ifs))
-            BOOST_LOG_TRIVIAL(info) << "The configuration file " << AppConfig::config_path() <<
+            BOOST_LOG_TRIVIAL(info) << "The configuration file " << AppConfig::loading_path() <<
             " has a wrong MD5 checksum or the checksum is missing. This may indicate a file corruption or a harmless user edit.";
 
         ifs.seekg(0, boost::nowide::ifstream::beg);
@@ -262,32 +262,32 @@ std::string AppConfig::load()
 #ifdef WIN32
         // The configuration file is corrupted, try replacing it with the backup configuration.
         ifs.close();
-        std::string backup_path = (boost::format("%1%.bak") % AppConfig::config_path()).str();
+        std::string backup_path = (boost::format("%1%.bak") % AppConfig::loading_path()).str();
         if (boost::filesystem::exists(backup_path)) {
             // Compute checksum of the configuration backup file and try to load configuration from it when the checksum is correct.
             boost::nowide::ifstream backup_ifs(backup_path);
             if (!verify_config_file_checksum(backup_ifs)) {
-                BOOST_LOG_TRIVIAL(error) << format("Both \"%1%\" and \"%2%\" are corrupted. It isn't possible to restore configuration from the backup.", AppConfig::config_path(), backup_path);
+                BOOST_LOG_TRIVIAL(error) << format("Both \"%1%\" and \"%2%\" are corrupted. It isn't possible to restore configuration from the backup.", AppConfig::loading_path(), backup_path);
                 backup_ifs.close();
                 boost::filesystem::remove(backup_path);
-            } else if (std::string error_message; copy_file(backup_path, AppConfig::config_path(), error_message, false) != SUCCESS) {
-                BOOST_LOG_TRIVIAL(error) << format("Configuration file \"%1%\" is corrupted. Failed to restore from backup \"%2%\": %3%", AppConfig::config_path(), backup_path, error_message);
+            } else if (std::string error_message; copy_file(backup_path, AppConfig::loading_path(), error_message, false) != SUCCESS) {
+                BOOST_LOG_TRIVIAL(error) << format("Configuration file \"%1%\" is corrupted. Failed to restore from backup \"%2%\": %3%", AppConfig::loading_path(), backup_path, error_message);
                 backup_ifs.close();
                 boost::filesystem::remove(backup_path);
             } else {
-                BOOST_LOG_TRIVIAL(info) << format("Configuration file \"%1%\" was corrupted. It has been succesfully restored from the backup \"%2%\".", AppConfig::config_path(), backup_path);
+                BOOST_LOG_TRIVIAL(info) << format("Configuration file \"%1%\" was corrupted. It has been succesfully restored from the backup \"%2%\".", AppConfig::loading_path(), backup_path);
                 // Try parse configuration file after restore from backup.
                 try {
-                    ifs.open(AppConfig::config_path());
+                    ifs.open(AppConfig::loading_path());
                     pt::read_ini(ifs, tree);
                     recovered = true;
                 } catch (pt::ptree_error& ex) {
-                    BOOST_LOG_TRIVIAL(info) << format("Failed to parse configuration file \"%1%\" after it has been restored from backup: %2%", AppConfig::config_path(), ex.what());
+                    BOOST_LOG_TRIVIAL(info) << format("Failed to parse configuration file \"%1%\" after it has been restored from backup: %2%", AppConfig::loading_path(), ex.what());
                 }
             }
         } else
 #endif // WIN32
-            BOOST_LOG_TRIVIAL(info) << format("Failed to parse configuration file \"%1%\": %2%", AppConfig::config_path(), ex.what());
+            BOOST_LOG_TRIVIAL(info) << format("Failed to parse configuration file \"%1%\": %2%", AppConfig::loading_path(), ex.what());
         if (! recovered) {
             // Report the initial error of parsing PrusaSlicer.ini.
             // Error while parsing config file. We'll customize the error message and rethrow to be displayed.

src/libslic3r/AppConfig.hpp

@@ -148,6 +148,9 @@ public:
 	// Does the config file exist?
 	bool 				exists();
 
+	void                set_loading_path(const std::string& path) { m_loading_path = path; }
+	std::string         loading_path() { return (m_loading_path.empty() ? config_path() : m_loading_path); }
+
     std::vector<std::string> get_recent_projects() const;
     void set_recent_projects(const std::vector<std::string>& recent_projects);
 
@@ -196,6 +199,8 @@ private:
 	Semver                                                      m_orig_version;
 	// Whether the existing version is before system profiles & configuration updating
 	bool                                                        m_legacy_datadir;
+
+	std::string                                                 m_loading_path;
 };
 
 } // namespace Slic3r

src/libslic3r/PresetBundle.cpp

@@ -188,6 +188,61 @@ void PresetBundle::setup_directories()
     }
 }
 
+// recursively copy all files and dirs in from_dir to to_dir
+static void copy_dir(const boost::filesystem::path& from_dir, const boost::filesystem::path& to_dir)
+{
+    if(!boost::filesystem::is_directory(from_dir))
+        return;
+    // i assume to_dir.parent surely exists
+    if (!boost::filesystem::is_directory(to_dir))
+        boost::filesystem::create_directory(to_dir);
+    for (auto& dir_entry : boost::filesystem::directory_iterator(from_dir)) {
+        if (!boost::filesystem::is_directory(dir_entry.path())) {
+            std::string em;
+            CopyFileResult cfr = copy_file(dir_entry.path().string(), (to_dir / dir_entry.path().filename()).string(), em, false);
+            if (cfr != SUCCESS) {
+                BOOST_LOG_TRIVIAL(error) << "Error when copying files from " << from_dir << " to " << to_dir << ": " << em;
+            }
+        } else {
+            copy_dir(dir_entry.path(), to_dir / dir_entry.path().filename());
+        }
+    }
+}
+
+void PresetBundle::copy_files(const std::string& from)
+{
+    boost::filesystem::path data_dir = boost::filesystem::path(Slic3r::data_dir());
+    // list of searched paths based on current directory system in setup_directories()
+    // do not copy cache and snapshots
+    boost::filesystem::path from_data_dir = boost::filesystem::path(from);
+    std::initializer_list<boost::filesystem::path> from_dirs= {
+        from_data_dir / "vendor",
+        from_data_dir / "shapes",
+#ifdef SLIC3R_PROFILE_USE_PRESETS_SUBDIR
+        // Store the print/filament/printer presets into a "presets" directory.
+        data_dir / "presets",
+        data_dir / "presets" / "print",
+        data_dir / "presets" / "filament",
+        data_dir / "presets" / "sla_print",
+        data_dir / "presets" / "sla_material",
+        data_dir / "presets" / "printer",
+        data_dir / "presets" / "physical_printer"
+#else
+        // Store the print/filament/printer presets at the same location as the upstream Slic3r.
+        from_data_dir / "print",
+        from_data_dir / "filament",
+        from_data_dir / "sla_print",
+        from_data_dir / "sla_material",
+        from_data_dir / "printer",
+        from_data_dir / "physical_printer"
+#endif
+    };
+    // copy recursively all files
+    for (const boost::filesystem::path& from_dir : from_dirs) {
+        copy_dir(from_dir, data_dir / from_dir.filename());
+    }
+}
+
 PresetsConfigSubstitutions PresetBundle::load_presets(AppConfig &config, ForwardCompatibilitySubstitutionRule substitution_rule, 
                                                       const PresetPreferences& preferred_selection/* = PresetPreferences()*/)
 {

src/libslic3r/PresetBundle.hpp

@@ -24,6 +24,7 @@ public:
     void            reset(bool delete_files);
 
     void            setup_directories();
+    void            copy_files(const std::string& from);
 
     struct PresetPreferences {
         std::string printer_model_id;// name of a preferred printer model

src/slic3r/GUI/GUI_App.cpp

@@ -743,6 +743,25 @@ bool GUI_App::init_opengl()
 #endif
 }
 
+// gets path to PrusaSlicer.ini, returns semver from first line comment
+static boost::optional<Semver> parse_semver_from_ini(std::string path)
+{
+    std::ifstream stream(path);
+    std::stringstream buffer;
+    buffer << stream.rdbuf();
+    std::string body = buffer.str();
+    size_t end_line = body.find_first_of("\n\r");
+    body.resize(end_line);
+    size_t start = body.find("PrusaSlicer ");
+    if (start == std::string::npos)
+        return boost::none;
+    body = body.substr(start + 12);
+    size_t end = body.find_first_of(" \n\r");
+    if (end < body.size())
+        body.resize(end);
+    return Semver::parse(body);
+}
+
 void GUI_App::init_app_config()
 {
 	// Profiles for the alpha are stored into the PrusaSlicer-alpha directory to not mix with the current release.
@@ -791,9 +810,110 @@ void GUI_App::init_app_config()
                     "\n\n" + app_config->config_path() + "\n\n" + error);
             }
         }
+        // Save orig_version here, so its empty if no app_config existed before this run.
+        m_last_config_version = app_config->orig_version();//parse_semver_from_ini(app_config->config_path());
     }
 }
 
+// returns true if found newer version and user agreed to use it
+bool GUI_App::check_older_app_config(Semver current_version, bool backup)
+{
+    // find other version app config (alpha / beta / release)
+    std::string             config_path = app_config->config_path();
+    boost::filesystem::path parent_file_path(config_path);
+    std::string             filename = parent_file_path.filename().string();
+    parent_file_path.remove_filename().remove_filename();
+
+    std::vector<boost::filesystem::path> candidates;
+
+    if (SLIC3R_APP_KEY "-alpha" != GetAppName()) candidates.emplace_back(parent_file_path / SLIC3R_APP_KEY "-alpha" / filename);
+    if (SLIC3R_APP_KEY "-beta" != GetAppName())  candidates.emplace_back(parent_file_path / SLIC3R_APP_KEY "-beta" / filename);
+    if (SLIC3R_APP_KEY != GetAppName())          candidates.emplace_back(parent_file_path / SLIC3R_APP_KEY / filename);
+
+    Semver last_semver = current_version;
+    for (const auto& candidate : candidates) {
+        if (boost::filesystem::exists(candidate)) {
+            // parse
+            boost::optional<Semver>other_semver = parse_semver_from_ini(candidate.string());
+            if (other_semver && *other_semver > last_semver) {
+                last_semver = *other_semver;
+                m_older_data_dir_path = candidate.parent_path().string();
+            }
+        }
+    }
+    if (m_older_data_dir_path.empty())
+        return false;
+    BOOST_LOG_TRIVIAL(info) << "last app config file used: " << m_older_data_dir_path;
+    // ask about using older data folder
+    wxRichMessageDialog msg(nullptr, backup ? 
+        wxString::Format(_L("PrusaSlicer detected another configuration folder at %s."
+            "\nIts version is %s." 
+            "\nLast version you used in current configuration folder is %s."
+            "\nPlease note that PrusaSlicer uses different folders to save configuration of alpha, beta and full release versions."
+            "\nWould you like to copy found configuration to your current configuration folder?"
+            
+            "\n\nIf you select yes, PrusaSlicer will copy all profiles and other files from found folder to the current one. Overwriting any existing file with matching name."
+            "\nIf you select no, you will continue with current configuration.")
+            , m_older_data_dir_path, last_semver.to_string(), current_version.to_string())
+        : wxString::Format(_L("PrusaSlicer detected another configuration folder at %s."
+            "\nIts version is %s."
+            "\nThere is no configuration file in current configuration folder."
+            "\nPlease note that PrusaSlicer uses different folders to save configuration of alpha, beta and full release versions."
+            "\nWould you like to copy found configuration to your current configuration folder?"
+
+            "\n\nIf you select yes, PrusaSlicer will copy all profiles and other files from found folder to the current one."
+            "\nIf you select no, you will start with clean installation with configuration wizard.")
+            , m_older_data_dir_path, last_semver.to_string())
+        , _L("PrusaSlicer"), wxICON_QUESTION | wxYES_NO);
+    if (msg.ShowModal() == wxID_YES) {
+        std::string snapshot_id;
+        if (backup) {
+            // configuration snapshot
+            std::string comment;
+            if (const Config::Snapshot* snapshot = Config::take_config_snapshot_report_error(
+                    *app_config, 
+                    Config::Snapshot::SNAPSHOT_USER, 
+                    comment);
+                    snapshot != nullptr)
+                // Is thos correct? Save snapshot id for later, when new app config is loaded.
+                snapshot_id = snapshot->id;
+            else
+                BOOST_LOG_TRIVIAL(error) << "Failed to take congiguration snapshot: ";
+        }
+
+        // This will tell later (when config folder structure is sure to exists) to copy files from m_older_data_dir_path
+        m_init_app_config_from_older = true;
+        // load app config from older file
+        app_config->set_loading_path((boost::filesystem::path(m_older_data_dir_path) / filename).string());
+        std::string error = app_config->load();
+        if (!error.empty()) {
+            // Error while parsing config file. We'll customize the error message and rethrow to be displayed.
+            if (is_editor()) {
+                throw Slic3r::RuntimeError(
+                    _u8L("Error parsing PrusaSlicer config file, it is probably corrupted. "
+                        "Try to manually delete the file to recover from the error. Your user profiles will not be affected.") +
+                    "\n\n" + app_config->config_path() + "\n\n" + error);
+            }
+            else {
+                throw Slic3r::RuntimeError(
+                    _u8L("Error parsing PrusaGCodeViewer config file, it is probably corrupted. "
+                        "Try to manually delete the file to recover from the error.") +
+                    "\n\n" + app_config->config_path() + "\n\n" + error);
+            }
+        }
+        if (!snapshot_id.empty())
+            app_config->set("on_snapshot", snapshot_id);
+        m_app_conf_exists = true;
+        return true;
+    }
+    return false;
+}
+
+void GUI_App::copy_older_config()
+{
+    preset_bundle->copy_files(m_older_data_dir_path);
+}
+
 void GUI_App::init_single_instance_checker(const std::string &name, const std::string &path)
 {
     BOOST_LOG_TRIVIAL(debug) << "init wx instance checker " << name << " "<< path; 
@@ -884,6 +1004,13 @@ bool GUI_App::on_init_inner()
         }
     }
 
+    if (m_last_config_version) {
+        if (*m_last_config_version < *Semver::parse(SLIC3R_VERSION))
+            check_older_app_config(*m_last_config_version, true);
+    } else {
+        check_older_app_config(Semver(), false);
+    }
+
     app_config->set("version", SLIC3R_VERSION);
     app_config->save();
 
@@ -922,12 +1049,18 @@ bool GUI_App::on_init_inner()
         scrn->SetText(_L("Loading configuration")+ dots);
     }
 
+    
+
     preset_bundle = new PresetBundle();
 
     // just checking for existence of Slic3r::data_dir is not enough : it may be an empty directory
     // supplied as argument to --datadir; in that case we should still run the wizard
     preset_bundle->setup_directories();
 
+    
+    if (m_init_app_config_from_older)
+        copy_older_config();
+
     if (is_editor()) {
 #ifdef __WXMSW__ 
         if (app_config->get("associate_3mf") == "1")

src/slic3r/GUI/GUI_App.hpp

@@ -337,6 +337,8 @@ public:
 private:
     bool            on_init_inner();
 	void            init_app_config();
+    bool            check_older_app_config(Semver current_version, bool backup);
+    void            copy_older_config();
     void            window_pos_save(wxTopLevelWindow* window, const std::string &name);
     void            window_pos_restore(wxTopLevelWindow* window, const std::string &name, bool default_maximized = false);
     void            window_pos_sanitize(wxTopLevelWindow* window);
@@ -344,6 +346,10 @@ private:
 
     bool            config_wizard_startup();
 	void            check_updates(const bool verbose);
+
+    bool                    m_init_app_config_from_older { false };
+    std::string             m_older_data_dir_path;
+    boost::optional<Semver> m_last_config_version;
 };
 
 DECLARE_APP(GUI_App)