diff --git a/src/LabelTrack.cpp b/src/LabelTrack.cpp
index f1b872841..c47065617 100644
--- a/src/LabelTrack.cpp
+++ b/src/LabelTrack.cpp
@@ -1012,7 +1012,7 @@ void LabelTrack::calculateFontHeight(wxDC & dc) const
    mFontHeight += CursorExtraHeight - (charLeading+charDescent);
 }
 
-bool LabelTrack::IsTextSelected()
+bool LabelTrack::IsTextSelected() const
 {
    if (mSelIndex == -1)
       return false;
diff --git a/src/LabelTrack.h b/src/LabelTrack.h
index e794cb075..bdd90d529 100644
--- a/src/LabelTrack.h
+++ b/src/LabelTrack.h
@@ -117,7 +117,7 @@ class AUDACITY_DLL_API LabelTrack final : public Track
 
    bool IsGoodLabelFirstKey(const wxKeyEvent & evt);
    bool IsGoodLabelEditKey(const wxKeyEvent & evt);
-   bool IsTextSelected();
+   bool IsTextSelected() const;
 
    void CreateCustomGlyphs();
    LabelTrack(const std::shared_ptr<DirManager> &projDirManager);
@@ -228,6 +228,7 @@ class AUDACITY_DLL_API LabelTrack final : public Track
 
    int GetNumLabels() const;
    const LabelStruct *GetLabel(int index) const;
+   const LabelArray &GetLabels() const { return mLabels; }
 
    //This returns the index of the label we just added.
    int AddLabel(const SelectedRegion &region, const wxString &title = {},
diff --git a/src/Menus.cpp b/src/Menus.cpp
index a97079400..767638328 100644
--- a/src/Menus.cpp
+++ b/src/Menus.cpp
@@ -30,6 +30,8 @@
 
 #include "Experimental.h"
 
+#include <wx/frame.h>
+
 #include "AdornedRulerPanel.h"
 #include "AudioIO.h"
 #include "LabelTrack.h"
@@ -414,55 +416,286 @@ CommandFlag MenuManager::GetFocusedFrame(AudacityProject &project)
 }
 
 
-ReservedCommandFlag::ReservedCommandFlag()
+// Really means, some track is selected, that isn't a time track
+const auto TracksSelectedPred =
+   [](const AudacityProject &project){
+      auto range = TrackList::Get( project ).Selected()
+        - []( const Track *pTrack ){
+           return track_cast<const TimeTrack*>( pTrack ); };
+      return !range.empty();
+   };
+
+const auto AudioIOBusyPred =
+   [](const AudacityProject &project ){
+      return AudioIOBase::Get()->IsAudioTokenActive(
+         ProjectAudioIO::Get( project ).GetAudioIOToken());
+   };
+
+const auto TimeSelectedPred =
+   [](const AudacityProject &project){
+      // This is equivalent to check if there is a valid selection,
+      // so it's used for Zoom to Selection too
+      return !ViewInfo::Get( project ).selectedRegion.isPoint();
+   };
+
+namespace{
+   using Predicates = std::vector< ReservedCommandFlag::Predicate >;
+   Predicates &RegisteredPredicates()
+   {
+      static Predicates thePredicates;
+      return thePredicates;
+   }
+}
+
+ReservedCommandFlag::ReservedCommandFlag( const Predicate &predicate )
 {
    static size_t sNextReservedFlag = 0;
    // This will throw std::out_of_range if the constant NCommandFlags is too
    // small
    set( sNextReservedFlag++ );
+   RegisteredPredicates().emplace_back( predicate );
 }
 
 const ReservedCommandFlag
-   AudioIONotBusyFlag,
-   TimeSelectedFlag, // This is equivalent to check if there is a valid selection, so it's used for Zoom to Selection too
-   TracksSelectedFlag,
-   TracksExistFlag,
-   LabelTracksExistFlag,
-   WaveTracksSelectedFlag,
-   ClipboardFlag,
-   TextClipFlag, // Same as Clipboard flag for now.
-   UnsavedChangesFlag,
-   HasLastEffectFlag,
-   UndoAvailableFlag,
-   RedoAvailableFlag,
-   ZoomInAvailableFlag,
-   ZoomOutAvailableFlag,
-   StereoRequiredFlag,  //lda
-   TopDockHasFocus,  //lll
-   TrackPanelHasFocus,  //lll
-   BotDockHasFocus,  //lll
-   LabelsSelectedFlag,
-   AudioIOBusyFlag,  //lll
-   PlayRegionLockedFlag,  //msmeyer
-   PlayRegionNotLockedFlag,  //msmeyer
-   CutCopyAvailableFlag,
-   WaveTracksExistFlag,
-   NoteTracksExistFlag,  //gsw
-   NoteTracksSelectedFlag,  //gsw
-   HaveRecentFiles,
-   IsNotSyncLockedFlag,  //awd
-   IsSyncLockedFlag,  //awd
-   IsRealtimeNotActiveFlag,  //lll
-   CaptureNotBusyFlag,
-   CanStopAudioStreamFlag,
-   RulerHasFocus, // prl
-   NotMinimizedFlag, // prl
-   PausedFlag, // jkc
-   NotPausedFlag, // jkc
-   HasWaveDataFlag, // jkc
-   PlayableTracksExistFlag,
-   AudioTracksSelectedFlag,
-   NoAutoSelect // jkc
+   AudioIONotBusyFlag{
+      [](const AudacityProject &project ){
+         return !AudioIOBusyPred( project );
+      }
+   },
+   TimeSelectedFlag{
+      TimeSelectedPred
+   },
+   TracksSelectedFlag{
+      TracksSelectedPred
+   },
+   TracksExistFlag{
+      [](const AudacityProject &project){
+         return !TrackList::Get( project ).Any().empty();
+      }
+   },
+   LabelTracksExistFlag{
+      [](const AudacityProject &project){
+         return !TrackList::Get( project ).Any<const LabelTrack>().empty();
+      }
+   },
+   WaveTracksSelectedFlag{
+      [](const AudacityProject &project){
+         return !TrackList::Get( project ).Selected<const WaveTrack>().empty();
+      }
+   },
+   UnsavedChangesFlag{
+      [](const AudacityProject &project){
+         auto &undoManager = UndoManager::Get( project );
+         return
+            undoManager.UnsavedChanges()
+         ||
+            !ProjectFileIO::Get( project ).IsProjectSaved()
+         ;
+      }
+   },
+   HasLastEffectFlag{
+      [](const AudacityProject &project){
+         return !MenuManager::Get( project ).mLastEffect.empty();
+      }
+   },
+   UndoAvailableFlag{
+      [](const AudacityProject &project){
+         return ProjectHistory::Get( project ).UndoAvailable();
+      }
+   },
+   RedoAvailableFlag{
+      [](const AudacityProject &project){
+         return ProjectHistory::Get( project ).RedoAvailable();
+      }
+   },
+   ZoomInAvailableFlag{
+      [](const AudacityProject &project){
+         return
+            ViewInfo::Get( project ).ZoomInAvailable()
+         &&
+            !TrackList::Get( project ).Any().empty()
+         ;
+      }
+   },
+   ZoomOutAvailableFlag{
+      [](const AudacityProject &project){
+         return
+            ViewInfo::Get( project ).ZoomOutAvailable()
+         &&
+            !TrackList::Get( project ).Any().empty()
+         ;
+      }
+   },
+   StereoRequiredFlag{
+      [](const AudacityProject &project){
+         // True iff at least one stereo track is selected, i.e., at least
+         // one right channel is selected.
+         // TODO: more-than-two-channels
+         auto range = TrackList::Get( project ).Selected<const WaveTrack>()
+            - &Track::IsLeader;
+         return !range.empty();
+      }
+   },  //lda
+   TrackPanelHasFocus{
+      [](const AudacityProject &project){
+         for (auto w = wxWindow::FindFocus(); w; w = w->GetParent()) {
+            if (dynamic_cast<const NonKeystrokeInterceptingWindow*>(w))
+               return true;
+         }
+         return false;
+      }
+   },  //lll
+   LabelsSelectedFlag{
+      [](const AudacityProject &project){
+         // At least one label track selected, having at least one label
+         // completely within the time selection.
+         const auto &selectedRegion = ViewInfo::Get( project ).selectedRegion;
+         const auto &test = [&]( const LabelTrack *pTrack ){
+            const auto &labels = pTrack->GetLabels();
+            return std::any_of( labels.begin(), labels.end(),
+               [&](const LabelStruct &label){
+                  return
+                     label.getT0() >= selectedRegion.t0()
+                  &&
+                     label.getT1() <= selectedRegion.t1()
+                  ;
+               }
+            );
+         };
+         auto range = TrackList::Get( project ).Selected<const LabelTrack>()
+            + test;
+         return !range.empty();
+      }
+   },
+   AudioIOBusyFlag{
+      AudioIOBusyPred
+   }, //lll
+   PlayRegionLockedFlag{
+      [](const AudacityProject &project){
+         return ViewInfo::Get(project).playRegion.Locked();
+      }
+   },  //msmeyer
+   PlayRegionNotLockedFlag{
+      [](const AudacityProject &project){
+         const auto &playRegion = ViewInfo::Get(project).playRegion;
+         return !playRegion.Locked() && !playRegion.Empty();
+      }
+   },  //msmeyer
+   CutCopyAvailableFlag{
+      [](const AudacityProject &project){
+         auto range = TrackList::Get( project ).Any<const LabelTrack>()
+            + &LabelTrack::IsTextSelected;
+         if ( !range.empty() )
+            return true;
+
+         if (
+            !AudioIOBusyPred( project )
+         &&
+            TimeSelectedPred( project )
+         &&
+            TracksSelectedPred( project )
+         )
+            return true;
+
+         return false;
+      }
+   },
+   WaveTracksExistFlag{
+      [](const AudacityProject &project){
+         return !TrackList::Get( project ).Any<const WaveTrack>().empty();
+      }
+   },
+   NoteTracksExistFlag{
+      [](const AudacityProject &project){
+         return !TrackList::Get( project ).Any<const NoteTrack>().empty();
+      }
+   },  //gsw
+   NoteTracksSelectedFlag{
+      [](const AudacityProject &project){
+         return !TrackList::Get( project ).Selected<const NoteTrack>().empty();
+      }
+   },  //gsw
+   IsNotSyncLockedFlag{
+      [](const AudacityProject &project){
+         return !ProjectSettings::Get( project ).IsSyncLocked();
+      }
+   },  //awd
+   IsSyncLockedFlag{
+      [](const AudacityProject &project){
+         return ProjectSettings::Get( project ).IsSyncLocked();
+      }
+   },  //awd
+   IsRealtimeNotActiveFlag{
+      [](const AudacityProject &){
+         return !EffectManager::Get().RealtimeIsActive();
+      }
+   },  //lll
+   CaptureNotBusyFlag{
+      [](const AudacityProject &){
+         auto gAudioIO = AudioIO::Get();
+         return !(
+            gAudioIO->IsBusy() &&
+            gAudioIO->GetNumCaptureChannels() > 0
+         );
+      }
+   },
+   CanStopAudioStreamFlag{
+      [](const AudacityProject &project){
+         return ControlToolBar::Get( project ).CanStopAudioStream();
+      }
+   },
+   NotMinimizedFlag{
+      [](const AudacityProject &project){
+         const wxWindow *focus = FindProjectFrame( &project );
+         if (focus) {
+            while (focus && focus->GetParent())
+               focus = focus->GetParent();
+         }
+         return (focus &&
+            !static_cast<const wxTopLevelWindow*>(focus)->IsIconized()
+         );
+      }
+   }, // prl
+   PausedFlag{
+      [](const AudacityProject&){
+         return AudioIOBase::Get()->IsPaused();
+      }
+   },
+   HasWaveDataFlag{
+      [](const AudacityProject &project){
+         auto range = TrackList::Get( project ).Any<const WaveTrack>()
+            + [](const WaveTrack *pTrack){
+               return pTrack->GetEndTime() > pTrack->GetStartTime();
+            };
+         return !range.empty();
+      }
+   }, // jkc
+   PlayableTracksExistFlag{
+      [](const AudacityProject &project){
+         auto &tracks = TrackList::Get( project );
+         return
+#ifdef EXPERIMENTAL_MIDI_OUT
+            !tracks.Any<const NoteTrack>().empty()
+         ||
+#endif
+            !tracks.Any<const WaveTrack>().empty()
+         ;
+      }
+   },
+   AudioTracksSelectedFlag{
+      [](const AudacityProject &project){
+         auto &tracks = TrackList::Get( project );
+         return
+            !tracks.Selected<const NoteTrack>().empty()
+            // even if not EXPERIMENTAL_MIDI_OUT
+         ||
+            tracks.Selected<const WaveTrack>().empty()
+         ;
+      }
+   },
+   NoAutoSelect{
+     [](const AudacityProject &){ return false; }
+   } // jkc
 ;
 
 CommandFlag MenuManager::GetUpdateFlags( bool checkActive )
diff --git a/src/ProjectFileIO.cpp b/src/ProjectFileIO.cpp
index a45f031c0..918ea8902 100644
--- a/src/ProjectFileIO.cpp
+++ b/src/ProjectFileIO.cpp
@@ -642,7 +642,7 @@ void ProjectFileIO::DeleteCurrentAutoSaveFile()
    }
 }
 
-bool ProjectFileIO::IsProjectSaved() {
+bool ProjectFileIO::IsProjectSaved() const {
    auto &project = mProject;
    auto &dirManager = DirManager::Get( project );
    // This is true if a project was opened from an .aup
diff --git a/src/ProjectFileIO.h b/src/ProjectFileIO.h
index 3130c09e6..c13f9d49a 100644
--- a/src/ProjectFileIO.h
+++ b/src/ProjectFileIO.h
@@ -40,7 +40,7 @@ public:
    // recovery file
    void SetProjectTitle( int number = -1 );
 
-   bool IsProjectSaved();
+   bool IsProjectSaved() const;
 
    void Reset();
    
diff --git a/src/ProjectHistory.cpp b/src/ProjectHistory.cpp
index 32356d29a..f5674dda3 100644
--- a/src/ProjectHistory.cpp
+++ b/src/ProjectHistory.cpp
@@ -59,7 +59,7 @@ void ProjectHistory::InitialState()
    undoManager.StateSaved();
 }
 
-bool ProjectHistory::UndoAvailable()
+bool ProjectHistory::UndoAvailable() const
 {
    auto &project = mProject;
    auto &tracks = TrackList::Get( project );
@@ -68,7 +68,7 @@ bool ProjectHistory::UndoAvailable()
        !tracks.HasPendingTracks();
 }
 
-bool ProjectHistory::RedoAvailable()
+bool ProjectHistory::RedoAvailable() const
 {
    auto &project = mProject;
    auto &tracks = TrackList::Get( project );
diff --git a/src/ProjectHistory.h b/src/ProjectHistory.h
index d425854e4..6e86d626e 100644
--- a/src/ProjectHistory.h
+++ b/src/ProjectHistory.h
@@ -31,8 +31,8 @@ public:
 
    void InitialState();
    void SetStateTo(unsigned int n);
-   bool UndoAvailable();
-   bool RedoAvailable();
+   bool UndoAvailable() const;
+   bool RedoAvailable() const;
    void PushState(const wxString &desc, const wxString &shortDesc); // use UndoPush::AUTOSAVE
    void PushState(const wxString &desc, const wxString &shortDesc, UndoPush flags);
    void RollbackState();
diff --git a/src/UndoManager.cpp b/src/UndoManager.cpp
index fa6ab15fa..c552581a3 100644
--- a/src/UndoManager.cpp
+++ b/src/UndoManager.cpp
@@ -388,7 +388,7 @@ void UndoManager::Redo(const Consumer &consumer)
    mProject.QueueEvent( safenew wxCommandEvent{ EVT_UNDO_OR_REDO } );
 }
 
-bool UndoManager::UnsavedChanges()
+bool UndoManager::UnsavedChanges() const
 {
    return (saved != current) || HasODChangesFlag();
 }
@@ -418,7 +418,7 @@ void UndoManager::SetODChangesFlag()
    mODChangesMutex.Unlock();
 }
 
-bool UndoManager::HasODChangesFlag()
+bool UndoManager::HasODChangesFlag() const
 {
    bool ret;
    mODChangesMutex.Lock();
diff --git a/src/UndoManager.h b/src/UndoManager.h
index fa383e3ce..a7b9b475b 100644
--- a/src/UndoManager.h
+++ b/src/UndoManager.h
@@ -152,7 +152,7 @@ class AUDACITY_DLL_API UndoManager
    bool UndoAvailable();
    bool RedoAvailable();
 
-   bool UnsavedChanges();
+   bool UnsavedChanges() const;
    void StateSaved();
 
    // Return value must first be calculated by CalculateSpaceUsage():
@@ -167,7 +167,7 @@ class AUDACITY_DLL_API UndoManager
 
    ///to mark as unsaved changes without changing the state/tracks.
    void SetODChangesFlag();
-   bool HasODChangesFlag();
+   bool HasODChangesFlag() const;
    void ResetODChangesFlag();
 
  private:
@@ -184,7 +184,7 @@ class AUDACITY_DLL_API UndoManager
    unsigned long long mClipboardSpaceUsage {};
 
    bool mODChanges;
-   ODLock mODChangesMutex;//mODChanges is accessed from many threads.
+   mutable ODLock mODChangesMutex;//mODChanges is accessed from many threads.
 
 };
 
diff --git a/src/commands/CommandFlag.h b/src/commands/CommandFlag.h
index f570abaa6..7260314a4 100644
--- a/src/commands/CommandFlag.h
+++ b/src/commands/CommandFlag.h
@@ -12,6 +12,9 @@
 // Flags used in command handling.
 
 #include <bitset>
+#include <functional>
+
+class AudacityProject;
 
 // Increase the template parameter as needed to allow more flags
 constexpr size_t NCommandFlags = 64;
@@ -30,10 +33,12 @@ constexpr CommandFlag
    NoFlagsSpecified{ ~0ULL }; // all ones
 
 // Construct one statically to register (and reserve) a bit position in the set
+// an associate it with a test function
 class ReservedCommandFlag : public CommandFlag
 {
 public:
-   ReservedCommandFlag();
+   using Predicate = std::function< bool( const AudacityProject& ) >;
+   ReservedCommandFlag( const Predicate & );
 };
 
 // Widely used command flags, but this list need not be exhaustive.  It may be
diff --git a/src/toolbars/ControlToolBar.cpp b/src/toolbars/ControlToolBar.cpp
index 5c4541dff..adcd3ae9e 100644
--- a/src/toolbars/ControlToolBar.cpp
+++ b/src/toolbars/ControlToolBar.cpp
@@ -824,7 +824,7 @@ void ControlToolBar::OnStop(wxCommandEvent & WXUNUSED(evt))
    }
 }
 
-bool ControlToolBar::CanStopAudioStream()
+bool ControlToolBar::CanStopAudioStream() const
 {
    auto gAudioIO = AudioIO::Get();
    return (!gAudioIO->IsStreamActive() ||
diff --git a/src/toolbars/ControlToolBar.h b/src/toolbars/ControlToolBar.h
index 6324bce82..d4d438490 100644
--- a/src/toolbars/ControlToolBar.h
+++ b/src/toolbars/ControlToolBar.h
@@ -99,7 +99,7 @@ class ControlToolBar final : public ToolBar {
    bool IsRecordDown() const;
 
    // A project is only allowed to stop an audio stream that it owns.
-   bool CanStopAudioStream ();
+   bool CanStopAudioStream () const;
 
    // Play currently selected region, or if nothing selected,
    // play from current cursor.
diff --git a/src/toolbars/ToolManager.cpp b/src/toolbars/ToolManager.cpp
index 35e2d79e9..696c9d0cf 100644
--- a/src/toolbars/ToolManager.cpp
+++ b/src/toolbars/ToolManager.cpp
@@ -1022,6 +1022,11 @@ ToolDock *ToolManager::GetTopDock()
    return mTopDock;
 }
 
+const ToolDock *ToolManager::GetTopDock() const
+{
+   return mTopDock;
+}
+
 //
 // Return a pointer to the bottom dock
 //
@@ -1030,6 +1035,11 @@ ToolDock *ToolManager::GetBotDock()
    return mBotDock;
 }
 
+const ToolDock *ToolManager::GetBotDock() const
+{
+   return mBotDock;
+}
+
 //
 // Queues an EVT_TOOLBAR_UPDATED command event to notify any
 // interest parties of an updated toolbar or dock layout
diff --git a/src/toolbars/ToolManager.h b/src/toolbars/ToolManager.h
index 673b76caf..820512645 100644
--- a/src/toolbars/ToolManager.h
+++ b/src/toolbars/ToolManager.h
@@ -68,7 +68,9 @@ class ToolManager final
    ToolBar *GetToolBar( int type ) const;
 
    ToolDock *GetTopDock();
+   const ToolDock *GetTopDock() const;
    ToolDock *GetBotDock();
+   const ToolDock *GetBotDock() const;
 
    void Reset();
    void Destroy();