ProjectHistory does not depend on ViewMenus ...

... Remove the last dependency by making the special vertical zoom fit on undo
push an event callback

src/Menus.h

@@ -134,7 +134,6 @@ void DoSelectSomething( AudacityProject &project );
 namespace ViewActions {
 double GetZoomOfToFit( const AudacityProject &project );
 void DoZoomFit( AudacityProject &project );
-void DoZoomFitV( AudacityProject &project );
 }
 
 /// Namespace for functions for Transport menu

src/ProjectHistory.cpp

@@ -11,10 +11,8 @@ Paul Licameli split from ProjectManager.cpp
 #include "ProjectHistory.h"
 
 #include "DirManager.h"
-#include "Menus.h"
 #include "Project.h"
 #include "ProjectFileIO.h"
-#include "ProjectSettings.h"
 #include "Tags.h"
 #include "Track.h"
 #include "TrackPanel.h"
@@ -91,7 +89,6 @@ void ProjectHistory::PushState(const wxString &desc,
 {
    auto &project = mProject;
    auto &projectFileIO = ProjectFileIO::Get( project );
-   const auto &settings = ProjectSettings::Get( project );
    auto &tracks = TrackList::Get( project );
    auto &viewInfo = ViewInfo::Get( project );
    auto &undoManager = UndoManager::Get( project );
@@ -102,8 +99,6 @@ void ProjectHistory::PushState(const wxString &desc,
 
    mDirty = true;
 
-   if (settings.GetTracksFitVerticallyZoomed())
-      ViewActions::DoZoomFitV( project );
    if((flags & UndoPush::AUTOSAVE) != UndoPush::MINIMAL)
       projectFileIO.AutoSave();
 }

src/menus/ViewMenus.cpp

@@ -8,6 +8,7 @@
 #include "../Prefs.h"
 #include "../Project.h"
 #include "../ProjectHistory.h"
+#include "../ProjectSettings.h"
 #include "../ProjectWindow.h"
 #include "../TrackPanel.h"
 #include "../UndoManager.h"
@@ -178,6 +179,9 @@ void DoZoomFit(AudacityProject &project)
    window.TP_ScrollWindow(start);
 }
 
+}
+
+namespace {
 void DoZoomFitV(AudacityProject &project)
 {
    auto &trackPanel = TrackPanel::Get( project );
@@ -205,10 +209,16 @@ void DoZoomFitV(AudacityProject &project)
    for (auto t : range)
       t->SetHeight(height);
 }
+}
+
+namespace ViewActions {
 
 // Menu handler functions
 
-struct Handler : CommandHandlerObject {
+struct Handler final
+   : CommandHandlerObject // MUST be the first base class!
+   , ClientData::Base
+{
 
 void OnZoomIn(const CommandContext &context)
 {
@@ -417,15 +427,40 @@ void OnShowEffectsRack(const CommandContext &WXUNUSED(context) )
 }
 #endif
 
+// Not a menu item, but a listener for events
+void OnUndoPushed( wxCommandEvent &evt )
+{
+   evt.Skip();
+   const auto &settings = ProjectSettings::Get( mProject );
+   if (settings.GetTracksFitVerticallyZoomed())
+      DoZoomFitV( mProject );
+}
+
+Handler( AudacityProject &project )
+   : mProject{ project }
+{
+   mProject.Bind( EVT_UNDO_PUSHED, &Handler::OnUndoPushed, this );
+}
+
+~Handler()
+{
+   mProject.Unbind( EVT_UNDO_PUSHED, &Handler::OnUndoPushed, this );
+}
+
+AudacityProject &mProject;
+
 }; // struct Handler
 
 } // namespace
 
-static CommandHandlerObject &findCommandHandler(AudacityProject &) {
-   // Handler is not stateful.  Doesn't need a factory registered with
-   // AudacityProject.
-   static ViewActions::Handler instance;
-   return instance;
+// Handler needs a back-reference to the project, so needs a factory registered
+// with AudacityProject.
+static const AudacityProject::AttachedObjects::RegisteredFactory key{
+   []( AudacityProject &project ) {
+      return std::make_unique< ViewActions::Handler >( project ); } };
+
+static CommandHandlerObject &findCommandHandler(AudacityProject &project) {
+   return project.AttachedObjects::Get< ViewActions::Handler >( key );
 };
 
 // Menu definitions