Reusable preference-populating code for other registries than Menus

src/Menus.cpp

@@ -42,7 +42,6 @@
 #include "widgets/AudacityMessageBox.h"
 #include "widgets/ErrorDialog.h"
 
-#include <mutex>
 #include <unordered_set>
 
 #include <wx/menu.h>
@@ -941,6 +940,22 @@ void Visit( Visitor &visitor, BaseItem *pTopItem, GroupItem *pRegistry )
       gPrefs->Flush();
 }
 
+OrderingPreferenceInitializer::OrderingPreferenceInitializer(
+   Literal root, const Pairs &pairs )
+{
+   bool doFlush = false;
+   for (const auto &pair : pairs) {
+      const auto key = wxString{'/'} + root + pair.first;
+      if ( gPrefs->Read(key).empty() ) {
+         gPrefs->Write( key, pair.second );
+         doFlush = true;
+      }
+   }
+   
+   if (doFlush)
+      gPrefs->Flush();
+}
+
 }
 
 /// CreateMenusAndCommands builds the menus, and also rebuilds them after
@@ -963,45 +978,6 @@ MenuTable::AttachedItem::AttachedItem(
 
 namespace {
 
-// Once only, cause initial population of preferences for the ordering
-// of some menu items that used to be given in tables 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 menus.
-// But this needs only to mention some strings -- there is no compilation or
-// link dependency of this source file on those other implementation files.
-void InitializeMenuOrdering()
-{
-   using Pair = std::pair<const wxChar *, const wxChar *>;
-   static const Pair pairs [] = {
-      {wxT(""), wxT(
-"File,Edit,Select,View,Transport,Tracks,Generate,Effect,Analyze,Tools,Window,Optional,Help"
-       )},
-      {wxT("/Optional/Extra/Part1"), wxT(
-"Transport,Tools,Mixer,Edit,PlayAtSpeed,Seek,Device,Select"
-       )},
-      {wxT("/Optional/Extra/Part2"), wxT(
-"Navigation,Focus,Cursor,Track,Scriptables1,Scriptables2"
-       )},
-      {wxT("/View/Windows"), wxT("UndoHistory,Karaoke,MixerBoard")},
-      {wxT("/Analyze/Analyzers/Windows"), wxT("ContrastAnalyser,PlotSpectrum")},
-      {wxT("/Transport/Basic"),wxT("Play,Record,Scrubbing,Cursor")},
-   };
-
-   bool doFlush = false;
-   for (auto pair : pairs) {
-      const auto key = wxString{'/'} + MenuPathStart + pair.first;
-      if ( gPrefs->Read(key).empty() ) {
-         gPrefs->Write( key, pair.second );
-         doFlush = true;
-      }
-   }
-   
-   if (doFlush)
-      gPrefs->Flush();
-}
-
 using namespace MenuTable;
 
 struct MenuItemVisitor : MenuVisitor
@@ -1105,8 +1081,31 @@ struct MenuItemVisitor : MenuVisitor
 
 void MenuCreator::CreateMenusAndCommands(AudacityProject &project)
 {
-   static std::once_flag flag;
+   // Once only, cause initial population of preferences for the ordering
-   std::call_once( flag, InitializeMenuOrdering );
+   // of some menu items that used to be given in tables 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 menus.
+   // 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{
+      MenuPathStart,
+      {
+         {wxT(""), wxT(
+   "File,Edit,Select,View,Transport,Tracks,Generate,Effect,Analyze,Tools,Window,Optional,Help"
+          )},
+         {wxT("/Optional/Extra/Part1"), wxT(
+   "Transport,Tools,Mixer,Edit,PlayAtSpeed,Seek,Device,Select"
+          )},
+         {wxT("/Optional/Extra/Part2"), wxT(
+   "Navigation,Focus,Cursor,Track,Scriptables1,Scriptables2"
+          )},
+         {wxT("/View/Windows"), wxT("UndoHistory,Karaoke,MixerBoard")},
+         {wxT("/Analyze/Analyzers/Windows"), wxT("ContrastAnalyser,PlotSpectrum")},
+         {wxT("/Transport/Basic"),wxT("Play,Record,Scrubbing,Cursor")},
+      }
+   };
 
    auto &commandManager = CommandManager::Get( project );
 

src/commands/CommandManager.h

@@ -645,6 +645,27 @@ namespace Registry {
       Visitor &visitor,
       BaseItem *pTopItem,
       GroupItem *pRegistry = nullptr );
+
+   // Typically a static object.  Constructor initializes certain preferences
+   // if they are not present.  These preferences determine an extrinsic
+   // visitation ordering for registered items.  This is needed in some
+   // places that have migrated from a system of exhaustive listings, to a
+   // registry of plug-ins, and something must be done to preserve old
+   // behavior.  It can be done in the central place using string literal
+   // identifiers only, not requiring static compilation or linkage dependency.
+   struct OrderingPreferenceInitializer {
+      using Literal = const wxChar *;
+      using Pair = std::pair< Literal, Literal >;
+      using Pairs = std::vector< Pair >;
+      OrderingPreferenceInitializer(
+         // Specifies the topmost preference section:
+         Literal root,
+         // Specifies /-separated Registry paths relative to root
+         // (these should be blank or start with / and not end with /),
+         // each with a ,-separated sequence of identifiers, which specify a
+         // desired ordering at one node of the tree:
+         const Pairs &pairs );
+   };
 }
 
 struct MenuVisitor : Registry::Visitor