Register preference pages, importers, exporters without sequence nos.

src/export/Export.cpp

@@ -282,6 +282,24 @@ BEGIN_EVENT_TABLE(Exporter, wxEvtHandler)
 END_EVENT_TABLE()
 
 namespace {
+const auto PathStart = wxT("Exporters");
+
+static Registry::GroupItem &sRegistry()
+{
+   static Registry::TransparentGroupItem<> registry{ PathStart };
+   return registry;
+}
+
+struct ExporterItem final : Registry::SingleItem {
+   ExporterItem(
+      const Identifier &id, const Exporter::ExportPluginFactory &factory )
+      : SingleItem{ id }
+      , mFactory{ factory }
+   {}
+
+   Exporter::ExportPluginFactory mFactory;
+};
+
    using ExportPluginFactories = std::vector< Exporter::ExportPluginFactory >;
    ExportPluginFactories &sFactories()
    {
@@ -291,15 +309,24 @@ namespace {
 }
 
 Exporter::RegisteredExportPlugin::RegisteredExportPlugin(
-   const ExportPluginFactory &factory )
+   const Identifier &id,
+   const ExportPluginFactory &factory,
+   const Registry::Placement &placement )
 {
    if ( factory )
-      sFactories().emplace_back( factory );
+      Registry::RegisterItem( sRegistry(), placement,
+         std::make_unique< ExporterItem >( id, factory ) );
 }
 
 Exporter::Exporter( AudacityProject &project )
 : mProject{ &project }
 {
+   using namespace Registry;
+   static OrderingPreferenceInitializer init{
+      PathStart,
+      { {wxT(""), wxT("PCM,MP3,OGG,FLAC,MP2,CommandLine,FFmpeg") } },
+   };
+
    mMixerSpec = NULL;
    mBook = NULL;
 
@@ -307,15 +334,25 @@ Exporter::Exporter( AudacityProject &project )
    for ( const auto &factory : sFactories() )
       mPlugins.emplace_back( factory() );
 
-   // The factories were pushed on the array at static initialization time in an
-   // unspecified sequence.  Sort according to the sequence numbers the plugins
-   // report to make the order determinate.
-   std::sort( mPlugins.begin(), mPlugins.end(),
-      []( const ExportPluginArray::value_type &a,
-          const ExportPluginArray::value_type &b ){
-         return a->SequenceNumber() < b->SequenceNumber();
+   struct MyVisitor final : Visitor {
+      MyVisitor()
+      {
+         // visit the registry to collect the plug-ins properly
+         // sorted
+         TransparentGroupItem<> top{ PathStart };
+         Registry::Visit( *this, &top, &sRegistry() );
       }
-   );
+
+      void Visit( SingleItem &item, const Path &path ) override
+      {
+         mPlugins.emplace_back(
+            static_cast<ExporterItem&>( item ).mFactory() );
+      }
+
+      ExportPluginArray mPlugins;
+   } visitor;
+
+   mPlugins.swap( visitor.mPlugins );
 
    SetFileDialogTitle( XO("Export Audio") );
 }

src/export/Export.h

@@ -19,6 +19,8 @@
 #include "../widgets/wxPanelWrapper.h" // to inherit
 #include "../FileNames.h" // for FileTypes
 
+#include "../commands/CommandManager.h" // for Registry::Placement
+
 class wxArrayString;
 class FileDialogWrapper;
 class wxFileCtrlEvent;
@@ -132,8 +134,6 @@ public:
                        const Tags *metadata = NULL,
                        int subformat = 0) = 0;
 
-   virtual unsigned SequenceNumber() const = 0;
-
 protected:
    std::unique_ptr<Mixer> CreateMixer(const TrackList &tracks,
          bool selectionOnly,
@@ -174,7 +174,10 @@ public:
    // to have some fresh state variables each time export begins again
    // and to compute translated strings for the current locale
    struct RegisteredExportPlugin{
-      RegisteredExportPlugin( const ExportPluginFactory& );
+      RegisteredExportPlugin(
+         const Identifier &id, // an internal string naming the plug-in
+         const ExportPluginFactory&,
+         const Registry::Placement &placement = { wxEmptyString, {} } );
    };
 
    static bool DoEditMetadata(AudacityProject &project,

src/export/ExportCL.cpp

@@ -310,8 +310,6 @@ public:
                MixerSpec *mixerSpec = NULL,
                const Tags *metadata = NULL,
                int subformat = 0) override;
-
-   virtual unsigned SequenceNumber() const override { return 60; }
 };
 
 ExportCL::ExportCL()
@@ -567,5 +565,6 @@ void ExportCL::OptionsCreate(ShuttleGui &S, int format)
    S.AddWindow( safenew ExportCLOptions{ S.GetParent(), format } );
 }
 
-static Exporter::RegisteredExportPlugin
-sRegisteredPlugin{ []{ return std::make_unique< ExportCL >(); } };
+static Exporter::RegisteredExportPlugin sRegisteredPlugin{ "CommandLine",
+   []{ return std::make_unique< ExportCL >(); }
+};

src/export/ExportFFmpeg.cpp

@@ -152,8 +152,6 @@ public:
       const Tags *metadata = NULL,
       int subformat = 0) override;
 
-   virtual unsigned SequenceNumber() const override { return 70; }
-
 private:
 
    AVOutputFormat  *   mEncFormatDesc{};       // describes our output file to libavformat
@@ -1141,8 +1139,9 @@ void ExportFFmpeg::OptionsCreate(ShuttleGui &S, int format)
    ExportPlugin::OptionsCreate(S, format);
 }
 
-static Exporter::RegisteredExportPlugin
-sRegisteredPlugin{ []{ return std::make_unique< ExportFFmpeg >(); } };
+static Exporter::RegisteredExportPlugin sRegisteredPlugin{ "FFmpeg",
+   []{ return std::make_unique< ExportFFmpeg >(); }
+};
 
 #endif
 

src/export/ExportFLAC.cpp

@@ -224,8 +224,6 @@ public:
                const Tags *metadata = NULL,
                int subformat = 0) override;
 
-   virtual unsigned SequenceNumber() const override { return 40; }
-
 private:
 
    bool GetMetadata(AudacityProject *project, const Tags *tags);
@@ -474,8 +472,9 @@ bool ExportFLAC::GetMetadata(AudacityProject *project, const Tags *tags)
    return true;
 }
 
-static Exporter::RegisteredExportPlugin
-sRegisteredPlugin{ []{ return std::make_unique< ExportFLAC >(); } };
+static Exporter::RegisteredExportPlugin sRegisteredPlugin{ "FLAC",
+   []{ return std::make_unique< ExportFLAC >(); }
+};
 
 #endif // USE_LIBFLAC
 

src/export/ExportMP2.cpp

@@ -217,8 +217,6 @@ public:
                const Tags *metadata = NULL,
                int subformat = 0) override;
 
-   virtual unsigned SequenceNumber() const override { return 50; }
-
 private:
 
    int AddTags(AudacityProject *project, ArrayOf<char> &buffer, bool *endOfFile, const Tags *tags);
@@ -498,8 +496,9 @@ void ExportMP2::AddFrame(struct id3_tag *tp, const wxString & n, const wxString
 }
 #endif
 
-static Exporter::RegisteredExportPlugin
-sRegisteredPlugin{ []{ return std::make_unique< ExportMP2 >(); } };
+static Exporter::RegisteredExportPlugin sRegisteredPlugin{ "MP2",
+   []{ return std::make_unique< ExportMP2 >(); }
+};
 
 #endif // #ifdef USE_LIBTWOLAME
 

src/export/ExportMP3.cpp

@@ -1687,8 +1687,6 @@ public:
                const Tags *metadata = NULL,
                int subformat = 0) override;
 
-   virtual unsigned SequenceNumber() const override { return 20; }
-
 private:
 
    int AskResample(int bitrate, int rate, int lowrate, int highrate);
@@ -2199,8 +2197,9 @@ void ExportMP3::AddFrame(struct id3_tag *tp, const wxString & n, const wxString
 }
 #endif
 
-static Exporter::RegisteredExportPlugin
-sRegisteredPlugin{ []{ return std::make_unique< ExportMP3 >(); } };
+static Exporter::RegisteredExportPlugin sRegisteredPlugin{ "MP3",
+   []{ return std::make_unique< ExportMP3 >(); }
+};
 
 //----------------------------------------------------------------------------
 // Return library version

src/export/ExportOGG.cpp

@@ -143,8 +143,6 @@ public:
                const Tags *metadata = NULL,
                int subformat = 0) override;
 
-   virtual unsigned SequenceNumber() const override { return 30; }
-
 private:
 
    bool FillComment(AudacityProject *project, vorbis_comment *comment, const Tags *metadata);
@@ -398,8 +396,9 @@ bool ExportOGG::FillComment(AudacityProject *project, vorbis_comment *comment, c
    return true;
 }
 
-static Exporter::RegisteredExportPlugin
-sRegisteredPlugin{ []{ return std::make_unique< ExportOGG >(); } };
+static Exporter::RegisteredExportPlugin sRegisteredPlugin{ "OGG",
+   []{ return std::make_unique< ExportOGG >(); }
+};
 
 #endif // USE_LIBVORBIS
 

src/export/ExportPCM.cpp

@@ -342,8 +342,6 @@ public:
    FileExtension GetExtension(int index) override;
    bool CheckFileName(wxFileName &filename, int format) override;
 
-   virtual unsigned SequenceNumber() const override { return 10; }
-
 private:
    void ReportTooBigError(wxWindow * pParent);
    ArrayOf<char> AdjustString(const wxString & wxStr, int sf_format);
@@ -971,5 +969,6 @@ bool ExportPCM::CheckFileName(wxFileName &filename, int format)
    return ExportPlugin::CheckFileName(filename, format);
 }
 
-static Exporter::RegisteredExportPlugin
-sRegisteredPlugin{ []{ return std::make_unique< ExportPCM >(); } };
+static Exporter::RegisteredExportPlugin sRegisteredPlugin{ "PCM",
+   []{ return std::make_unique< ExportPCM >(); }
+};

src/import/Import.cpp

@@ -84,11 +84,33 @@ ImportPluginList &Importer::sImportPluginList()
    return theList;
 }
 
+namespace {
+static const auto PathStart = wxT("Importers");
+
+static Registry::GroupItem &sRegistry()
+{
+   static Registry::TransparentGroupItem<> registry{ PathStart };
+   return registry;
+}
+
+struct ImporterItem final : Registry::SingleItem {
+   ImporterItem( const Identifier &id, std::unique_ptr<ImportPlugin> pPlugin )
+      : SingleItem{ id }
+      , mpPlugin{ std::move( pPlugin ) }
+   {}
+
+   std::unique_ptr<ImportPlugin> mpPlugin;
+};
+}
+
 Importer::RegisteredImportPlugin::RegisteredImportPlugin(
-   std::unique_ptr<ImportPlugin> pPlugin )
+   const Identifier &id,
+   std::unique_ptr<ImportPlugin> pPlugin,
+   const Registry::Placement &placement )
 {
    if ( pPlugin )
-      sImportPluginList().emplace_back( std::move( pPlugin ) );
+      Registry::RegisterItem( sRegistry(), placement,
+         std::make_unique< ImporterItem >( id, std::move( pPlugin ) ) );
 }
 
 UnusableImportPluginList &Importer::sUnusableImportPluginList()
@@ -110,16 +132,29 @@ bool Importer::Initialize()
    // order is significant.  If none match, they will all be tried
    // in the order defined here.
 
-   // They were pushed on the array at static initialization time in an
-   // unspecified sequence.  Sort according to the sequence numbers they
-   // report to make the order determinate.
-   auto &list = sImportPluginList();
-   std::sort( list.begin(), list.end(),
-      []( const ImportPluginList::value_type &a,
-          const ImportPluginList::value_type &b ){
-         return a->SequenceNumber() < b->SequenceNumber();
+   using namespace Registry;
+   static OrderingPreferenceInitializer init{
+      PathStart,
+      { {wxT(""), wxT("PCM,OGG,FLAC,MP3,LOF,FFmpeg") } }
+      // QT and GStreamer are only conditionally compiled and would get
+      // placed at the end if present
+   };
+   
+   static struct MyVisitor final : Visitor {
+      MyVisitor()
+      {
+         // Once only, visit the registry to collect the plug-ins properly
+         // sorted
+         TransparentGroupItem<> top{ PathStart };
+         Registry::Visit( *this, &top, &sRegistry() );
       }
-   );
+
+      void Visit( SingleItem &item, const Path &path ) override
+      {
+         sImportPluginList().push_back(
+            static_cast<ImporterItem&>( item ).mpPlugin.get() );
+      }
+   } visitor;
 
    // Ordering of the unusable plugin list is not important.
 
@@ -292,7 +327,7 @@ void Importer::ReadImportItems()
          {
             if (importPlugin->GetPluginStringID() == new_item->filters[i])
             {
-               new_item->filter_objects.push_back(importPlugin.get());
+               new_item->filter_objects.push_back(importPlugin);
                found = true;
                break;
             }
@@ -307,7 +342,7 @@ void Importer::ReadImportItems()
          bool found = false;
          for (size_t i = 0; i < new_item->filter_objects.size(); i++)
          {
-            if (importPlugin.get() == new_item->filter_objects[i])
+            if (importPlugin == new_item->filter_objects[i])
             {
                found = true;
                break;
@@ -323,7 +358,7 @@ void Importer::ReadImportItems()
                new_item->filters.begin() + index,
                importPlugin->GetPluginStringID());
             new_item->filter_objects.insert(
-               new_item->filter_objects.begin() + index, importPlugin.get());
+               new_item->filter_objects.begin() + index, importPlugin);
             if (new_item->divider >= 0)
                new_item->divider++;
          }
@@ -402,7 +437,7 @@ std::unique_ptr<ExtImportItem> Importer::CreateDefaultImportItem()
    for (const auto &importPlugin : sImportPluginList())
    {
       new_item->filters.push_back(importPlugin->GetPluginStringID());
-      new_item->filter_objects.push_back(importPlugin.get());
+      new_item->filter_objects.push_back(importPlugin);
    }
    new_item->divider = -1;
    return new_item;
@@ -462,7 +497,7 @@ bool Importer::Import( AudacityProject &project,
          {
             // This plugin corresponds to user-selected filter, try it first.
             wxLogDebug(wxT("Inserting %s"),plugin->GetPluginStringID());
-            importPlugins.insert(importPlugins.begin(), plugin.get());
+            importPlugins.insert(importPlugins.begin(), plugin);
          }
       }
    }
@@ -532,14 +567,14 @@ bool Importer::Import( AudacityProject &project,
    // is not changed by user selection overrides or any other mechanism, but we include an assert
    // in case subsequent code revisions to the constructor should break this assumption that
    // libsndfile is first.
-   ImportPlugin *libsndfilePlugin = sImportPluginList().begin()->get();
+   ImportPlugin *libsndfilePlugin = *sImportPluginList().begin();
    wxASSERT(libsndfilePlugin->GetPluginStringID() == wxT("libsndfile"));
 
    for (const auto &plugin : sImportPluginList())
    {
       // Make sure its not already in the list
       if (importPlugins.end() ==
-          std::find(importPlugins.begin(), importPlugins.end(), plugin.get()))
+          std::find(importPlugins.begin(), importPlugins.end(), plugin))
       {
          if (plugin->SupportsExtension(extension))
          {
@@ -562,7 +597,7 @@ bool Importer::Import( AudacityProject &project,
                }
             }
             wxLogDebug(wxT("Appending %s"),plugin->GetPluginStringID());
-            importPlugins.push_back(plugin.get());
+            importPlugins.push_back(plugin);
          }
       }
    }
@@ -577,10 +612,10 @@ bool Importer::Import( AudacityProject &project,
       {
          // Make sure its not already in the list
          if (importPlugins.end() ==
-             std::find(importPlugins.begin(), importPlugins.end(), plugin.get()))
+             std::find(importPlugins.begin(), importPlugins.end(), plugin))
          {
             wxLogDebug(wxT("Appending %s"),plugin->GetPluginStringID());
-            importPlugins.push_back(plugin.get());
+            importPlugins.push_back(plugin);
          }
       }
    }

src/import/Import.h

@@ -20,6 +20,8 @@
 #include "../widgets/wxPanelWrapper.h" // to inherit
 #include "../FileNames.h" // for FileType
 
+#include "../commands/CommandManager.h" // for Registry::Placement
+
 class wxArrayString;
 class wxListBox;
 class AudacityProject;
@@ -80,7 +82,10 @@ public:
    // Objects of this type are statically constructed in files implementing
    // subclasses of ImportPlugin
    struct RegisteredImportPlugin{
-      RegisteredImportPlugin( std::unique_ptr<ImportPlugin> );
+      RegisteredImportPlugin(
+         const Identifier &id, // an internal string naming the plug-in
+         std::unique_ptr<ImportPlugin>,
+         const Registry::Placement &placement = { wxEmptyString, {} } );
    };
 
    // Objects of this type are statically constructed in files, to identify

src/import/ImportFFmpeg.cpp

@@ -185,8 +185,6 @@ public:
    ///! Probes the file and opens it if appropriate
    std::unique_ptr<ImportFileHandle> Open(
       const FilePath &Filename, AudacityProject*) override;
-   
-   unsigned SequenceNumber() const override;
 };
 
 ///! Does acual import, returned by FFmpegImportPlugin::Open
@@ -335,12 +333,7 @@ std::unique_ptr<ImportFileHandle> FFmpegImportPlugin::Open(
    return std::move(handle);
 }
 
-unsigned FFmpegImportPlugin::SequenceNumber() const
-{
-   return 60;
-}
-
-static Importer::RegisteredImportPlugin registered{
+static Importer::RegisteredImportPlugin registered{ "FFmpeg",
    std::make_unique< FFmpegImportPlugin >()
 };
 

src/import/ImportFLAC.cpp

@@ -137,8 +137,6 @@ class FLACImportPlugin final : public ImportPlugin
    TranslatableString GetPluginFormatDescription() override;
    std::unique_ptr<ImportFileHandle> Open(
       const FilePath &Filename, AudacityProject*)  override;
-
-   unsigned SequenceNumber() const override;
 };
 
 
@@ -334,12 +332,7 @@ std::unique_ptr<ImportFileHandle> FLACImportPlugin::Open(
    return std::move(handle);
 }
 
-unsigned FLACImportPlugin::SequenceNumber() const
-{
-   return 30;
-}
-
-static Importer::RegisteredImportPlugin registered{
+static Importer::RegisteredImportPlugin registered{ "FLAC",
    std::make_unique< FLACImportPlugin >()
 };
 

src/import/ImportForwards.h

@@ -16,7 +16,7 @@ class ImportPlugin;
 class UnusableImportPlugin;
 
 using ImportPluginList =
-   std::vector< std::unique_ptr<ImportPlugin> >;
+   std::vector< ImportPlugin * >;
 using UnusableImportPluginList =
    std::vector< std::unique_ptr<UnusableImportPlugin> >;
 

src/import/ImportGStreamer.cpp

@@ -249,8 +249,6 @@ public:
    ///! Probes the file and opens it if appropriate
    std::unique_ptr<ImportFileHandle> Open(
       const wxString &Filename, AudacityProject*) override;
-
-   unsigned SequenceNumber() const override;
 };
 
 // ============================================================================
@@ -261,7 +259,8 @@ public:
 // Instantiate GStreamerImportPlugin and add to the list of known importers
 
 static
-Importer::RegisteredImportPlugin{ []() -> std::unique_ptr< ImportPlugin > {
+Importer::RegisteredImportPlugin{ "GStreamer",
+   []() -> std::unique_ptr< ImportPlugin > {
    wxLogMessage(_TS("Audacity is built against GStreamer version %d.%d.%d-%d"),
                 GST_VERSION_MAJOR,
                 GST_VERSION_MINOR,
@@ -1152,11 +1151,6 @@ GStreamerImportFileHandle::Import(TrackFactory *trackFactory,
    return updateResult;
 }
 
-unsigned GStreamerImportPlugin::SequenceNumber() const
-{
-   return 80;
-}
-
 // ----------------------------------------------------------------------------
 // Message handlers
 // ----------------------------------------------------------------------------

src/import/ImportLOF.cpp

@@ -116,8 +116,6 @@ public:
    TranslatableString GetPluginFormatDescription() override;
    std::unique_ptr<ImportFileHandle> Open(
       const FilePath &Filename, AudacityProject *pProject) override;
-
-   unsigned SequenceNumber() const override;
 };
 
 
@@ -272,12 +270,7 @@ ProgressResult LOFImportFileHandle::Import(
    return ProgressResult::Success;
 }
 
-unsigned LOFImportPlugin::SequenceNumber() const
-{
-   return 50;
-}
-
-static Importer::RegisteredImportPlugin registered{
+static Importer::RegisteredImportPlugin registered{ "LOF",
    std::make_unique< LOFImportPlugin >()
 };
 

src/import/ImportMP3.cpp

@@ -117,8 +117,6 @@ public:
    TranslatableString GetPluginFormatDescription() override;
    std::unique_ptr<ImportFileHandle> Open(
       const FilePath &Filename, AudacityProject*) override;
-
-   unsigned SequenceNumber() const override;
 };
 
 class MP3ImportFileHandle final : public ImportFileHandle
@@ -257,12 +255,7 @@ ProgressResult MP3ImportFileHandle::Import(
    return privateData.updateResult;
 }
 
-unsigned MP3ImportPlugin::SequenceNumber() const
-{
-   return 40;
-}
-
-static Importer::RegisteredImportPlugin registered{
+static Importer::RegisteredImportPlugin registered{ "MP3",
    std::make_unique< MP3ImportPlugin >()
 };
 

src/import/ImportOGG.cpp

@@ -91,8 +91,6 @@ public:
    TranslatableString GetPluginFormatDescription() override;
    std::unique_ptr<ImportFileHandle> Open(
       const FilePath &Filename, AudacityProject*) override;
-
-   unsigned SequenceNumber() const override;
 };
 
 
@@ -215,12 +213,7 @@ std::unique_ptr<ImportFileHandle> OggImportPlugin::Open(
    return std::make_unique<OggImportFileHandle>(filename, std::move(file), std::move(vorbisFile));
 }
 
-unsigned OggImportPlugin::SequenceNumber() const
-{
-   return 20;
-}
-
-static Importer::RegisteredImportPlugin registered{
+static Importer::RegisteredImportPlugin registered{ "OGG",
    std::make_unique< OggImportPlugin >()
 };
 

src/import/ImportPCM.cpp

@@ -89,8 +89,6 @@ public:
    TranslatableString GetPluginFormatDescription() override;
    std::unique_ptr<ImportFileHandle> Open(
       const FilePath &Filename, AudacityProject*) override;
-
-   unsigned SequenceNumber() const override;
 };
 
 
@@ -192,12 +190,7 @@ std::unique_ptr<ImportFileHandle> PCMImportPlugin::Open(
    return std::make_unique<PCMImportFileHandle>(filename, std::move(file), info);
 }
 
-unsigned PCMImportPlugin::SequenceNumber() const
-{
-   return 10;
-}
-
-static Importer::RegisteredImportPlugin registered{
+static Importer::RegisteredImportPlugin registered{ "PCM",
    std::make_unique< PCMImportPlugin >()
 };
 

src/import/ImportPlugin.h

@@ -96,8 +96,6 @@ public:
    virtual std::unique_ptr<ImportFileHandle> Open(
       const FilePath &Filename, AudacityProject*) = 0;
 
-   virtual unsigned SequenceNumber() const = 0;
-
    virtual ~ImportPlugin() { }
 
 protected:

src/import/ImportQT.cpp

@@ -125,8 +125,6 @@ class QTImportPlugin final : public ImportPlugin
    std::unique_ptr<ImportFileHandle> Open(
       const wxString & Filename, AudacityProject*) override;
 
-   unsigned SequenceNumber() const override;
-
  private:
    bool mInitialized;
 };
@@ -222,12 +220,7 @@ std::unique_ptr<ImportFileHandle> QTImportPlugin::Open(
    return std::make_unique<QTImportFileHandle>(Filename, theMovie);
 }
 
-unsigned QTImportPlugin::SequenceNumber() const
-{
-   return 70;
-}
-
-static Importer::RegisteredImportPlugin registered{
+static Importer::RegisteredImportPlugin registered{ "QT",
    std::make_unique< QTImportPlugin >()
 };
 

src/prefs/BatchPrefs.cpp

@@ -97,12 +97,16 @@ BatchPrefs::~BatchPrefs()
 
 #if 0
 namespace{
-PrefsPanel::Registration sAttachment{ 190,
+PrefsPanel::Registration sAttachment{ "Batch",
    [](wxWindow *parent, wxWindowID winid, AudacityProject *)
    {
       wxASSERT(parent); // to justify safenew
       return safenew BatchPrefs(parent, winid);
-   }
+   },
+   false,
+   // Register with an explicit ordering hint because this one is
+   // only conditionally compiled
+   { "", { Registry::OrderingHint::Before, "KeyConfig" } }
 };
 }
 #endif

src/prefs/DevicePrefs.cpp

@@ -423,7 +423,7 @@ bool DevicePrefs::Commit()
 }
 
 namespace{
-PrefsPanel::Registration sAttachment{ 10,
+PrefsPanel::Registration sAttachment{ "Device",
    [](wxWindow *parent, wxWindowID winid, AudacityProject *)
    {
       wxASSERT(parent); // to justify safenew

src/prefs/DirectoriesPrefs.cpp

@@ -300,7 +300,7 @@ DirectoriesPrefsFactory() {
 }
 
 namespace{
-PrefsPanel::Registration sAttachment{ 150,
+PrefsPanel::Registration sAttachment{ "Directories",
    DirectoriesPrefsFactory() };
 };
 

src/prefs/EffectsPrefs.cpp

@@ -251,7 +251,7 @@ bool EffectsPrefs::Commit()
 }
 
 namespace{
-PrefsPanel::Registration sAttachment{ 170,
+PrefsPanel::Registration sAttachment{ "Effects",
    [](wxWindow *parent, wxWindowID winid, AudacityProject *)
    {
       wxASSERT(parent); // to justify safenew

src/prefs/ExtImportPrefs.cpp

@@ -827,11 +827,14 @@ void ExtImportPrefsDropTarget::OnLeave()
 }
 
 namespace{
-PrefsPanel::Registration sAttachment{ 120,
+PrefsPanel::Registration sAttachment{ "ExtImport",
    [](wxWindow *parent, wxWindowID winid, AudacityProject *)
    {
       wxASSERT(parent); // to justify safenew
       return safenew ExtImportPrefs(parent, winid);
-   }
+   },
+   false,
+   // Place as a lower level of the tree of pages:
+   { "ImportExport" }
 };
 }

src/prefs/GUIPrefs.cpp

@@ -382,7 +382,7 @@ int ShowClippingPrefsID()
 }
 
 namespace{
-PrefsPanel::Registration sAttachment{ 60,
+PrefsPanel::Registration sAttachment{ "GUI",
    [](wxWindow *parent, wxWindowID winid, AudacityProject *)
    {
       wxASSERT(parent); // to justify safenew

src/prefs/ImportExportPrefs.cpp

@@ -150,12 +150,11 @@ bool ImportExportPrefs::Commit()
 }
 
 namespace{
-PrefsPanel::Registration sAttachment{ 110,
+PrefsPanel::Registration sAttachment{ "ImportExport",
    [](wxWindow *parent, wxWindowID winid, AudacityProject *)
    {
       wxASSERT(parent); // to justify safenew
       return safenew ImportExportPrefs(parent, winid);
-   },
-   1
+   }
 };
 }

src/prefs/KeyConfigPrefs.cpp

@@ -890,7 +890,7 @@ KeyConfigPrefsFactory( const CommandID &name )
    };
 }
 namespace{
-PrefsPanel::Registration sAttachment{ 200,
+PrefsPanel::Registration sAttachment{ "KeyConfig",
    KeyConfigPrefsFactory()
 };
 }

src/prefs/LibraryPrefs.cpp

@@ -263,12 +263,16 @@ bool LibraryPrefs::Commit()
 
 #if !defined(DISABLE_DYNAMIC_LOADING_FFMPEG) || !defined(DISABLE_DYNAMIC_LOADING_LAME)
 namespace{
-PrefsPanel::Registration sAttachment{ 140,
+PrefsPanel::Registration sAttachment{ "Library",
    [](wxWindow *parent, wxWindowID winid, AudacityProject *)
    {
       wxASSERT(parent); // to justify safenew
       return safenew LibraryPrefs(parent, winid);
-   }
+   },
+   false,
+   // Register with an explicit ordering hint because this one is
+   // only conditionally compiled
+   { "", { Registry::OrderingHint::Before, "Directories" } }
 };
 }
 #endif

src/prefs/MidiIOPrefs.cpp

@@ -303,12 +303,16 @@ bool MidiIOPrefs::Validate()
 
 #ifdef EXPERIMENTAL_MIDI_OUT
 namespace{
-PrefsPanel::Registration sAttachment{ 40,
+PrefsPanel::Registration sAttachment{ "MidiIO",
    [](wxWindow *parent, wxWindowID winid, AudacityProject *)
    {
       wxASSERT(parent); // to justify safenew
       return safenew MidiIOPrefs(parent, winid);
-   }
+   },
+   false,
+   // Register with an explicit ordering hint because this one is
+   // only conditionally compiled
+   { "", { Registry::OrderingHint::After, "Recording" } }
 };
 }
 #endif

src/prefs/ModulePrefs.cpp

@@ -191,12 +191,16 @@ void ModulePrefs::SetModuleStatus(const FilePath &fname, int iStatus){
 
 #ifdef EXPERIMENTAL_MODULE_PREFS
 namespace{
-PrefsPanel::Registration sAttachment{ 220,
+PrefsPanel::Registration sAttachment{ "Module",
    [](wxWindow *parent, wxWindowID winid, AudacityProject *)
    {
       wxASSERT(parent); // to justify safenew
       return safenew ModulePrefs(parent, winid);
-   }
+   },
+   false,
+   // Register with an explicit ordering hint because this one is
+   // only conditionally compiled
+   { "", { Registry::OrderingHint::After, "Mouse" } }
 };
 }
 #endif

src/prefs/MousePrefs.cpp

@@ -223,7 +223,7 @@ bool MousePrefs::Commit()
 }
 
 namespace{
-PrefsPanel::Registration sAttachment{ 210,
+PrefsPanel::Registration sAttachment{ "Mouse",
    [](wxWindow *parent, wxWindowID winid, AudacityProject *)
    {
       wxASSERT(parent); // to justify safenew

src/prefs/PlaybackPrefs.cpp

@@ -183,7 +183,7 @@ bool PlaybackPrefs::Commit()
 }
 
 namespace{
-PrefsPanel::Registration sAttachment{ 20,
+PrefsPanel::Registration sAttachment{ "Playback",
    [](wxWindow *parent, wxWindowID winid, AudacityProject *)
    {
       wxASSERT(parent); // to justify safenew

src/prefs/PrefsDialog.cpp

@@ -39,6 +39,7 @@
 #include "../AudioIOBase.h"
 #include "../Prefs.h"
 #include "../ShuttleGui.h"
+#include "../commands/CommandManager.h"
 
 #include "PrefsPanel.h"
 
@@ -452,46 +453,101 @@ int wxTreebookExt::SetSelection(size_t n)
 }
 
 namespace {
-   struct Entry{
-      unsigned sequenceNumber;
-      PrefsDialog::PrefsNode node;
 
-      bool operator < ( const Entry &other ) const
-      { return sequenceNumber < other.sequenceNumber; }
-   };
-   using Entries = std::vector< Entry >;
-   Entries &Registry()
+struct PrefsItem final : Registry::ConcreteGroupItem<false> {
+   PrefsPanel::Factory factory;
+   bool expanded{ false };
+
+   PrefsItem( const wxString &name,
+      const PrefsPanel::Factory &factory_, bool expanded_ )
+         : ConcreteGroupItem<false>{ name }
+         , factory{ factory_ }, expanded{ expanded_ }
+   {}
+};
+
+// Collects registry tree nodes into a vector, in preorder.
+struct PrefsItemVisitor final : Registry::Visitor {
+   PrefsItemVisitor( PrefsDialog::Factories &factories_ )
+      : factories{ factories_ }
    {
-      static Entries result;
-      return result;
+      childCounts.push_back( 0 );
    }
+   void BeginGroup( Registry::GroupItem &item, const Path & ) override
+   {
+      auto pItem = dynamic_cast<PrefsItem*>( &item );
+      if (!pItem)
+         return;
+      indices.push_back( factories.size() );
+      factories.emplace_back( pItem->factory, 0, pItem->expanded );
+      ++childCounts.back();
+      childCounts.push_back( 0 );
+   }
+   void EndGroup( Registry::GroupItem &item, const Path & ) override
+   {
+      auto pItem = dynamic_cast<PrefsItem*>( &item );
+      if (!pItem)
+         return;
+      auto &factory = factories[ indices.back() ];
+      factory.nChildren = childCounts.back();
+      childCounts.pop_back();
+      indices.pop_back();
+   }
+
+   PrefsDialog::Factories &factories;
+   std::vector<size_t> childCounts;
+   std::vector<size_t> indices;
+};
+
+
+const auto PathStart = wxT("Preferences");
+   
 }
 
-PrefsPanel::Registration::Registration( unsigned sequenceNumber,
-   const Factory &factory,
-   unsigned nChildren,
-   bool expanded )
+
+namespace {
+static Registry::GroupItem &sRegistry()
 {
-   auto &registry = Registry();
-   Entry entry{ sequenceNumber, { factory, nChildren, expanded } };
-   const auto end = registry.end();
-   // Find insertion point:
-   auto iter = std::lower_bound( registry.begin(), end, entry );
-   // There should not be duplicate sequence numbers:
-   wxASSERT( iter == end || entry < *iter );
-   registry.insert( iter, entry );
+   static Registry::TransparentGroupItem<> registry{ PathStart };
+   return registry;
+}
+}
+
+PrefsPanel::Registration::Registration( const wxString &name,
+   const Factory &factory, bool expanded,
+   const Registry::Placement &placement )
+{
+   Registry::RegisterItem( sRegistry(), placement,
+      std::make_unique< PrefsItem >( name, factory, expanded ) );
 }
 
 PrefsDialog::Factories
 &PrefsDialog::DefaultFactories()
 {
+   // Once only, cause initial population of preferences for the ordering
+   // of some preference pages that used to be given in a table but are now
+   // separately registered in several .cpp files; the sequence of registration
+   // depends on unspecified accidents of static initialization order across
+   // compilation units, so we need something specific here to preserve old
+   // default appearance of the preference dialog.
+   // But this needs only to mention some strings -- there is no compilation or
+   // link dependency of this source file on those other implementation files.
+   static Registry::OrderingPreferenceInitializer init{
+      PathStart,
+      {
+         {wxT(""),
+       wxT("Device,Playback,Recording,Quality,GUI,Tracks,ImportExport,Directories,Warnings,Effects,KeyConfig,Mouse")
+         },
+         {wxT("/Tracks"), wxT("TracksBehaviors,Spectrum")},
+      }
+   };
+
    static Factories factories;
    static std::once_flag flag;
 
    std::call_once( flag, []{
-      for ( const auto &entry : Registry() ) {
-         factories.push_back( entry.node );
-      }
+      PrefsItemVisitor visitor{ factories };
+      Registry::TransparentGroupItem<> top{ PathStart };
+      Registry::Visit( visitor, &top, &sRegistry() );
    } );
    return factories;
 }

src/prefs/PrefsDialog.h

@@ -39,8 +39,8 @@ class PrefsDialog /* not final */ : public wxDialogWrapper
          std::function< PrefsPanel * (
             wxWindow *parent, wxWindowID winid, AudacityProject *) >;
        Factory factory;
-       unsigned nChildren;
-       bool expanded;
+       size_t nChildren{ 0 };
+       bool expanded{ false };
 
        PrefsNode(const Factory &factory_,
           unsigned nChildren_ = 0,

src/prefs/PrefsPanel.h

@@ -30,6 +30,7 @@ MousePrefs, QualityPrefs, SpectrumPrefs and ThemePrefs.
 #include <functional>
 #include "../widgets/wxPanelWrapper.h" // to inherit
 #include "../include/audacity/ComponentInterface.h"
+#include "../commands/CommandManager.h"
 
 /* A few constants for an attempt at semi-uniformity */
 #define PREFS_FONT_SIZE     8
@@ -61,10 +62,9 @@ class PrefsPanel /* not final */ : public wxPanelWrapper, ComponentInterface
    // also implements the PrefsPanel subclass.
    struct Registration final
    {
-      Registration( unsigned sequenceNumber,
-         const Factory &factory,
-         unsigned nChildren = 0,
-         bool expanded = true );
+      Registration( const wxString &name, const Factory &factory,
+         bool expanded = true,
+         const Registry::Placement &placement = { wxEmptyString, {} });
    };
 
    PrefsPanel(wxWindow * parent,

src/prefs/ProjectsPrefs.cpp

@@ -99,12 +99,16 @@ bool ProjectsPrefs::Commit()
 
 #ifdef EXPERIMENTAL_OD_DATA
 namespace{
-PrefsPanel::Registration sAttachment{ 130,
+PrefsPanel::Registration sAttachment{ "Projects",
    [](wxWindow *parent, wxWindowID winid, AudacityProject *)
    {
       wxASSERT(parent); // to justify safenew
       return safenew ProjectsPrefs(parent, winid);
-   }
+   },
+   false,
+   // Register with an explicit ordering hint because this one is
+   // only conditionally compiled
+   { "", { Registry::OrderingHint::After, "ImportExport" } }
 };
 }
 #endif

src/prefs/QualityPrefs.cpp

@@ -234,7 +234,7 @@ bool QualityPrefs::Commit()
 }
 
 namespace{
-PrefsPanel::Registration sAttachment{ 50,
+PrefsPanel::Registration sAttachment{ "Quality",
    [](wxWindow *parent, wxWindowID winid, AudacityProject *)
    {
       wxASSERT(parent); // to justify safenew

src/prefs/RecordingPrefs.cpp

@@ -305,7 +305,7 @@ void RecordingPrefs::OnToggleCustomName(wxCommandEvent & /* Evt */)
 }
 
 namespace{
-PrefsPanel::Registration sAttachment{ 30,
+PrefsPanel::Registration sAttachment{ "Recording",
    [](wxWindow *parent, wxWindowID winid, AudacityProject *)
    {
       wxASSERT(parent); // to justify safenew

src/prefs/SpectrumPrefs.cpp

@@ -602,8 +602,10 @@ SpectrumPrefsFactory( WaveTrack *wt )
 }
 
 namespace{
-PrefsPanel::Registration sAttachment{ 100,
+PrefsPanel::Registration sAttachment{ "Spectrum",
    SpectrumPrefsFactory( nullptr ),
-   false
+   false,
+   // Place it at a lower tree level
+   { "Tracks" }
 };
 }

src/prefs/ThemePrefs.cpp

@@ -233,12 +233,16 @@ bool ThemePrefs::Commit()
 
 #ifdef EXPERIMENTAL_THEME_PREFS
 namespace{
-PrefsPanel::Registration sAttachment{ 180,
+PrefsPanel::Registration sAttachment{ "Theme",
    [](wxWindow *parent, wxWindowID winid, AudacityProject *)
    {
       wxASSERT(parent); // to justify safenew
       return safenew ThemePrefs(parent, winid);
-   }
+   },
+   false,
+   // Register with an explicit ordering hint because this one is
+   // only conditionally compiled
+   { "", { Registry::OrderingHint::After, "Effects" } }
 };
 }
 #endif

src/prefs/TracksBehaviorsPrefs.cpp

@@ -132,11 +132,14 @@ bool TracksBehaviorsPrefs::Commit()
 }
 
 namespace{
-PrefsPanel::Registration sAttachment{ 90,
+PrefsPanel::Registration sAttachment{ "TracksBehaviors",
    [](wxWindow *parent, wxWindowID winid, AudacityProject *)
    {
       wxASSERT(parent); // to justify safenew
       return safenew TracksBehaviorsPrefs(parent, winid);
-   }
+   },
+   false,
+   // Place it at a lower tree level
+   { "Tracks" }
 };
 }

src/prefs/TracksPrefs.cpp

@@ -448,12 +448,11 @@ bool TracksPrefs::Commit()
 }
 
 namespace{
-PrefsPanel::Registration sAttachment{ 70,
+PrefsPanel::Registration sAttachment{ "Tracks",
    [](wxWindow *parent, wxWindowID winid, AudacityProject *)
    {
       wxASSERT(parent); // to justify safenew
       return safenew TracksPrefs(parent, winid);
-   },
-   2
+   }
 };
 }

src/prefs/WarningsPrefs.cpp

@@ -107,7 +107,7 @@ bool WarningsPrefs::Commit()
 }
 
 namespace{
-PrefsPanel::Registration sAttachment{ 160,
+PrefsPanel::Registration sAttachment{ "Warnings",
    [](wxWindow *parent, wxWindowID winid, AudacityProject *)
    {
       wxASSERT(parent); // to justify safenew

src/prefs/WaveformPrefs.cpp

@@ -265,9 +265,12 @@ WaveformPrefsFactory(WaveTrack *wt)
 }
 #if 0
 namespace{
-PrefsPanel::Registration sAttachment{ 80,
+PrefsPanel::Registration sAttachment{ "Waveform",
    WaveformPrefsFactory( nullptr ),
-   false
+   false,
+   // Register with an explicit ordering hint because this one is
+   // only conditionally compiled; and place it at a lower tree level
+   { "Tracks", { Registry::OrderingHint::Before, "Spectrum" } }
 };
 }
 #endif