TrackList emits more events for certain changes of state of tracks...

... Also rewrote some of the existing event handling so all events from
TrackList are of the same, custom event class, and distinguishing addition
from resizing events, though this distinction is not yet used

src/Track.h

@@ -205,8 +205,10 @@ class AUDACITY_DLL_API Track /* not final */
    wxString       mName;
    wxString       mDefaultName;
 
+ private:
    bool           mSelected;
 
+ protected:
    bool           mLinked;
    bool           mMinimized;
 
@@ -367,7 +369,7 @@ private:
    virtual void Merge(const Track &orig);
 
    wxString GetName() const { return mName; }
-   void SetName( const wxString &n ) { mName = n; }
+   void SetName( const wxString &n );
    wxString GetDefaultName() const { return mDefaultName; }
    void SetDefaultName( const wxString &n ) { mDefaultName = n; }
 
@@ -714,6 +716,11 @@ public:
    // Checks if sync-lock is on and any track in its sync-lock group is selected.
    bool IsSyncLockSelected() const;
 
+   // Send an event to listeners when state of the track changes
+   // To do: define values for the argument to distinguish different parts
+   // of the state, perhaps with wxNewId
+   void Notify( int code = -1 );
+
    // An always-true predicate useful for defining iterators
    bool Any() const;
 
@@ -763,8 +770,8 @@ public:
 
    bool GetMute    () const { return mMute;     }
    bool GetSolo    () const { return mSolo;     }
-   void SetMute    (bool m) { mMute     = m; }
-   void SetSolo    (bool s) { mSolo     = s; }
+   void SetMute    (bool m);
+   void SetSolo    (bool s);
 
    void Init( const PlayableTrack &init );
    void Merge( const Track &init ) override;
@@ -1086,31 +1093,50 @@ template <
  * Clear, and Contains, plus serialization of the list of tracks.
  */
 
-struct TrackListEvent : public wxCommandEvent
+struct TrackListEvent : public wxEvent
 {
-   TrackListEvent(wxEventType commandType = wxEVT_NULL, int winid = 0)
-   : wxCommandEvent{ commandType, winid } {}
+   explicit
+   TrackListEvent(
+      wxEventType commandType,
+      const std::weak_ptr<Track> &pTrack = {}, int code = -1)
+   : wxEvent{ commandType }
+   , mpTrack{ pTrack }
+   , mCode{ code }
+   {}
 
    TrackListEvent( const TrackListEvent& ) = default;
 
    wxEvent *Clone() const override { return new TrackListEvent(*this); }
 
    std::weak_ptr<Track> mpTrack;
+   int mCode;
 };
 
+// Posted when the set of selected tracks changes.
+wxDECLARE_EXPORTED_EVENT(AUDACITY_DLL_API,
+                         EVT_TRACKLIST_SELECTION_CHANGE, TrackListEvent);
+
+// Posted when certain fields of a track change.
+wxDECLARE_EXPORTED_EVENT(AUDACITY_DLL_API,
+                         EVT_TRACKLIST_TRACK_DATA_CHANGE, TrackListEvent);
+
 // Posted when tracks are reordered but otherwise unchanged.
 wxDECLARE_EXPORTED_EVENT(AUDACITY_DLL_API,
-                         EVT_TRACKLIST_PERMUTED, wxCommandEvent);
+                         EVT_TRACKLIST_PERMUTED, TrackListEvent);
 
-// Posted when some track was added or changed its height.
-// Cast to TrackListEvent and examine mpTrack to retrieve it.
+// Posted when some track changed its height.
 wxDECLARE_EXPORTED_EVENT(AUDACITY_DLL_API,
-                         EVT_TRACKLIST_RESIZING, wxCommandEvent);
+                         EVT_TRACKLIST_RESIZING, TrackListEvent);
+
+// Posted when a track has been added to a tracklist.
+// Also posted when one track replaces another
+wxDECLARE_EXPORTED_EVENT(AUDACITY_DLL_API,
+                         EVT_TRACKLIST_ADDITION, TrackListEvent);
 
 // Posted when a track has been deleted from a tracklist.
 // Also posted when one track replaces another
 wxDECLARE_EXPORTED_EVENT(AUDACITY_DLL_API,
-                         EVT_TRACKLIST_DELETION, wxCommandEvent);
+                         EVT_TRACKLIST_DELETION, TrackListEvent);
 
 class TrackList final : public wxEvtHandler, public ListOfTracks
 {
@@ -1495,8 +1521,11 @@ private:
    }
 
    void RecalcPositions(TrackNodePointer node);
+   void SelectionEvent( const std::shared_ptr<Track> &pTrack );
    void PermutationEvent();
+   void DataEvent( const std::shared_ptr<Track> &pTrack, int code );
    void DeletionEvent();
+   void AdditionEvent(TrackNodePointer node);
    void ResizingEvent(TrackNodePointer node);
 
    void SwapNodes(TrackNodePointer s1, TrackNodePointer s2);