Use a hook to implement the shift-click shortcut to keyboard prefs...

This frees EIGHTEEN files from the big strongly connected component!!

They are:

Dependencies
Export
ExportCL
ExportFFmpeg
ExportFFmpegDialogs
ExportFLAC
EportMP2
ExportMP3
ExportOGG
ExportPCM
ExtImportPrefs
Import
ImportRaw
KeyConfigPrefs
KeyView
LibraryPrefs
PrefsDialog
SpectrumPrefs

... and that includes all of the remaining *Prefs files.

It does still leave the nine Export* files in a smaller s.c.c, which could be
broken with a registration system, as was done for import at commit e2cf1d9

src/AudacityApp.cpp

@@ -108,6 +108,10 @@ It handles initialization and termination by subclassing wxApp.
 #include "tracks/ui/Scrubbing.h"
 #include "widgets/FileHistory.h"
 
+#ifdef EXPERIMENTAL_EASY_CHANGE_KEY_BINDINGS
+#include "../prefs/KeyConfigPrefs.h"
+#endif
+
 //temporarily commented out till it is added to all projects
 //#include "Profiler.h"
 
@@ -1593,6 +1597,23 @@ bool AudacityApp::OnInit()
    mTimer.SetOwner(this, kAudacityAppTimerID);
    mTimer.Start(200);
 
+#ifdef EXPERIMENTAL_EASY_CHANGE_KEY_BINDINGS
+   CommandManager::SetMenuHook( [](const CommandID &id){
+      if (::wxGetMouseState().ShiftDown()) {
+         // Only want one page of the preferences
+         PrefsDialog::Factories factories;
+         factories.push_back(KeyConfigPrefsFactory( id ));
+         auto pWindow = FindProjectFrame( GetActiveProject() );
+         GlobalPrefsDialog dialog( pWindow, factories );
+         dialog.ShowModal();
+         MenuCreator::RebuildAllMenuBars();
+         return true;
+      }
+      else
+         return false;
+   } );
+#endif
+
    return TRUE;
 }
 

src/commands/CommandManager.cpp

@@ -170,6 +170,20 @@ const CommandManager &CommandManager::Get( const AudacityProject &project )
    return Get( const_cast< AudacityProject & >( project ) );
 }
 
+static CommandManager::MenuHook &sMenuHook()
+{
+   static CommandManager::MenuHook theHook;
+   return theHook;
+}
+
+auto CommandManager::SetMenuHook( const MenuHook &hook ) -> MenuHook
+{
+   auto &theHook = sMenuHook();
+   auto result = theHook;
+   theHook = hook;
+   return result;
+}
+
 ///
 ///  Standard Constructor
 ///
@@ -1272,24 +1286,13 @@ bool CommandManager::HandleCommandEntry(const CommandListEntry * entry,
 ///CommandManagerListener function.  If you pass any flags,
 ///the command won't be executed unless the flags are compatible
 ///with the command's flags.
-#include "../prefs/PrefsDialog.h"
-#include "../prefs/KeyConfigPrefs.h"
 bool CommandManager::HandleMenuID(int id, CommandFlag flags, CommandMask mask)
 {
    CommandListEntry *entry = mCommandNumericIDHash[id];
 
-#ifdef EXPERIMENTAL_EASY_CHANGE_KEY_BINDINGS
-   if (::wxGetMouseState().ShiftDown()) {
-      // Only want one page of the preferences
-      PrefsDialog::Factories factories;
-      factories.push_back(KeyConfigPrefsFactory( entry->name ));
-      auto pWindow = FindProjectFrame( GetActiveProject() );
-      GlobalPrefsDialog dialog( pWindow, factories );
-      dialog.ShowModal();
-      MenuCreator::RebuildAllMenuBars();
+   auto hook = sMenuHook();
+   if (hook && hook(entry->name))
       return true;
-   }
-#endif
 
    return HandleCommandEntry( entry, flags, mask );
 }

src/commands/CommandManager.h

@@ -108,6 +108,13 @@ class AUDACITY_DLL_API CommandManager final
    static CommandManager &Get( AudacityProject &project );
    static const CommandManager &Get( const AudacityProject &project );
 
+   // Type of a function that can intercept menu item handling.
+   // If it returns true, bypass the usual dipatch of commands.
+   using MenuHook = std::function< bool(const CommandID&) >;
+
+   // install a menu hook, returning the previously installed one
+   static MenuHook SetMenuHook( const MenuHook &hook );
+
    //
    // Constructor / Destructor
    //