Don't call QuitAudacity directly from src/menus...

... This cuts link dependency on AudacityApp.cpp, and allows the function to
be private to that file

src/Audacity.h

@@ -109,9 +109,6 @@
 
 class wxWindow;
 
-void QuitAudacity(bool bForce);
-void QuitAudacity();
-
 // Please try to support unlimited path length instead of using PLATFORM_MAX_PATH!
 // Define one constant for maximum path value, so we don't have to do
 // platform-specific conditionals everywhere we want to check it.

src/AudacityApp.cpp

@@ -266,7 +266,7 @@ static void wxOnAssert(const wxChar *fileName, int lineNumber, const wxChar *msg
 static bool gInited = false;
 static bool gIsQuitting = false;
 
-void QuitAudacity(bool bForce)
+static void QuitAudacity(bool bForce)
 {
    // guard against recursion
    if (gIsQuitting)
@@ -323,7 +323,7 @@ void QuitAudacity(bool bForce)
    }
 }
 
-void QuitAudacity()
+static void QuitAudacity()
 {
    QuitAudacity(false);
 }
@@ -647,9 +647,14 @@ BEGIN_EVENT_TABLE(AudacityApp, wxApp)
    EVT_MENU(wxID_OPEN, AudacityApp::OnMenuOpen)
    EVT_MENU(wxID_ABOUT, AudacityApp::OnMenuAbout)
    EVT_MENU(wxID_PREFERENCES, AudacityApp::OnMenuPreferences)
-   EVT_MENU(wxID_EXIT, AudacityApp::OnMenuExit)
 #endif
 
+   // Associate the handler with the menu id on all operating systems, even
+   // if they don't have an application menu bar like in macOS, so that
+   // other parts of the program can send the application a shut-down
+   // event
+   EVT_MENU(wxID_EXIT, AudacityApp::OnMenuExit)
+
 #ifndef __WXMSW__
    EVT_SOCKET(ID_IPC_SERVER, AudacityApp::OnServerEvent)
    EVT_SOCKET(ID_IPC_SOCKET, AudacityApp::OnSocketEvent)

src/AudacityApp.h

@@ -39,9 +39,6 @@ class AppCommandEvent;
 class AudacityLogger;
 class AudacityProject;
 
-void QuitAudacity(bool bForce);
-void QuitAudacity();
-
 class AliasBlockFile;
 
 class AudacityApp final : public wxApp {

src/Project.cpp

@@ -2784,7 +2784,9 @@ void AudacityProject::OnCloseWindow(wxCloseEvent & event)
 
 #if !defined(__WXMAC__)
       if (quitOnClose) {
-         QuitAudacity();
+         // Simulate the application Exit menu item
+         wxCommandEvent evt{ wxEVT_MENU, wxID_EXIT };
+         wxTheApp->AddPendingEvent( evt );
       }
       else {
          AllProjects::Reset();

src/menus/FileMenus.cpp

@@ -542,7 +542,9 @@ void OnPrint(const CommandContext &context)
 
 void OnExit(const CommandContext &WXUNUSED(context) )
 {
-   QuitAudacity();
+   // Simulate the application Exit menu item
+   wxCommandEvent evt{ wxEVT_MENU, wxID_EXIT };
+   wxTheApp->AddPendingEvent( evt );
 }
 
 }; // struct Handler

src/menus/TransportMenus.cpp

@@ -457,7 +457,11 @@ void OnTimerRecord(const CommandContext &context)
          // No action required
          break;
       case POST_TIMER_RECORD_CLOSE:
-         wxTheApp->CallAfter( []{ QuitAudacity(); } );
+         wxTheApp->CallAfter( []{
+            // Simulate the application Exit menu item
+            wxCommandEvent evt{ wxEVT_MENU, wxID_EXIT };
+            wxTheApp->AddPendingEvent( evt );
+         } );
          break;
       case POST_TIMER_RECORD_RESTART:
          // Restart System