From 4339c0df688ac9641358cf509856c9e43b213b6a Mon Sep 17 00:00:00 2001
From: Paul Licameli <paul.licameli@audacityteam.org>
Date: Sat, 22 Jun 2019 08:39:20 -0400
Subject: [PATCH 1/6] Move height calculation utilities to class TrackView

---
 src/Printing.cpp                    |  3 ++-
 src/ProjectWindow.cpp               |  3 ++-
 src/Track.cpp                       | 22 ----------------------
 src/Track.h                         |  3 ---
 src/TrackPanel.cpp                  | 14 ++++----------
 src/commands/GetInfoCommand.cpp     |  2 +-
 src/menus/ViewMenus.cpp             |  5 ++---
 src/tracks/ui/TrackSelectHandle.cpp |  5 +++--
 src/tracks/ui/TrackView.cpp         | 23 +++++++++++++++++++++++
 src/tracks/ui/TrackView.h           |  9 +++++++++
 10 files changed, 46 insertions(+), 43 deletions(-)

diff --git a/src/Printing.cpp b/src/Printing.cpp
index b14eb7393..481b470fa 100644
--- a/src/Printing.cpp
+++ b/src/Printing.cpp
@@ -72,7 +72,8 @@ bool AudacityPrintout::OnPrintPage(int WXUNUSED(page))
    dc->GetSize(&width, &height);
 
    int rulerScreenHeight = 40;
-   int screenTotalHeight = mTracks->GetHeight() + rulerScreenHeight;
+   int screenTotalHeight =
+      TrackView::GetTotalHeight( *mTracks ) + rulerScreenHeight;
 
    double scale = height / (double)screenTotalHeight;
 
diff --git a/src/ProjectWindow.cpp b/src/ProjectWindow.cpp
index e0b944730..effa0cc8f 100644
--- a/src/ProjectWindow.cpp
+++ b/src/ProjectWindow.cpp
@@ -29,6 +29,7 @@ Paul Licameli split from AudacityProject.cpp
 #include "toolbars/ControlToolBar.h"
 #include "toolbars/ToolManager.h"
 #include "tracks/ui/Scrubbing.h"
+#include "tracks/ui/TrackView.h"
 #include "widgets/wxPanelWrapper.h"
 #include "widgets/WindowAccessible.h"
 
@@ -1137,7 +1138,7 @@ void ProjectWindow::FixScrollbars()
    bool refresh = false;
    bool rescroll = false;
 
-   int totalHeight = (tracks.GetHeight() + 32);
+   int totalHeight = TrackView::GetTotalHeight( tracks ) + 32;
 
    int panelWidth, panelHeight;
    trackPanel.GetTracksUsableArea(&panelWidth, &panelHeight);
diff --git a/src/Track.cpp b/src/Track.cpp
index 8d34889ec..4b9fae1fd 100644
--- a/src/Track.cpp
+++ b/src/Track.cpp
@@ -842,15 +842,6 @@ Track *TrackList::GetPrev(Track * t, bool linked) const
    return nullptr;
 }
 
-/// For mono track height of track
-/// For stereo track combined height of both channels.
-int TrackList::GetGroupHeight(const Track * t) const
-{
-   const auto GetHeight = []( const Track *track )
-      { return TrackView::Get( *track ).GetHeight(); };
-   return Channels(t).sum( GetHeight );
-}
-
 bool TrackList::CanMoveUp(Track * t) const
 {
    return GetPrev(t, true) != NULL;
@@ -970,19 +961,6 @@ size_t TrackList::size() const
    return cnt;
 }
 
-int TrackList::GetHeight() const
-{
-   int height = 0;
-
-   if (!empty()) {
-      auto track = getPrev( getEnd() ).first->get();
-      auto &view = TrackView::Get( *track );
-      height = view.GetY() + view.GetHeight();
-   }
-
-   return height;
-}
-
 namespace {
    // Abstract the common pattern of the following three member functions
    inline double Accumulate
diff --git a/src/Track.h b/src/Track.h
index 74b1bfba6..321124153 100644
--- a/src/Track.h
+++ b/src/Track.h
@@ -1360,8 +1360,6 @@ public:
    /// Make the list empty
    void Clear(bool sendEvent = true);
 
-   int GetGroupHeight(const Track * t) const;
-
    bool CanMoveUp(Track * t) const;
    bool CanMoveDown(Track * t) const;
 
@@ -1393,7 +1391,6 @@ public:
    double GetEndTime() const;
 
    double GetMinOffset() const;
-   int GetHeight() const;
 
 #if LEGACY_PROJECT_FILE_SUPPORT
    // File I/O
diff --git a/src/TrackPanel.cpp b/src/TrackPanel.cpp
index 65b221f21..914cfa25b 100644
--- a/src/TrackPanel.cpp
+++ b/src/TrackPanel.cpp
@@ -832,10 +832,8 @@ void TrackPanel::RefreshTrack(Track *trk, bool refreshbacking)
 
    trk = *GetTracks()->FindLeader(trk);
    auto &view = TrackView::Get( *trk );
-   const auto GetHeight = []( const Track *track )
-      { return TrackView::Get( *track ).GetHeight(); };
    auto height =
-      TrackList::Channels(trk).sum( GetHeight )
+      TrackList::Channels(trk).sum( TrackView::GetTrackHeight )
       - kTopInset - kShadowThickness;
 
    // subtract insets and shadows from the rectangle, but not border
@@ -1327,9 +1325,7 @@ void TrackPanel::EnsureVisible(Track * t)
       trackTop += trackHeight;
 
       auto channels = TrackList::Channels(it);
-      const auto GetHeight = []( const Track *track )
-         { return TrackView::Get( *track ).GetHeight(); };
-      trackHeight = channels.sum( GetHeight );
+      trackHeight = channels.sum( TrackView::GetTrackHeight );
 
       //We have found the track we want to ensure is visible.
       if (channels.contains(t)) {
@@ -1363,15 +1359,13 @@ void TrackPanel::VerticalScroll( float fracPosition){
    int trackHeight = 0;
 
    auto tracks = GetTracks();
-   const auto GetHeight =
-      [&]( const Track *t ){ return tracks->GetGroupHeight(t); };
 
    auto range = tracks->Leaders();
    if (!range.empty()) {
-      trackHeight = GetHeight( *range.rbegin() );
+      trackHeight = TrackView::GetChannelGroupHeight( *range.rbegin() );
       --range.second;
    }
-   trackTop = range.sum( GetHeight );
+   trackTop = range.sum( TrackView::GetChannelGroupHeight );
 
    int delta;
    
diff --git a/src/commands/GetInfoCommand.cpp b/src/commands/GetInfoCommand.cpp
index 36eaa5513..8ea5d3f8a 100644
--- a/src/commands/GetInfoCommand.cpp
+++ b/src/commands/GetInfoCommand.cpp
@@ -497,7 +497,7 @@ bool GetInfoCommand::SendTracks(const CommandContext & context)
       context.AddBool( (trk == fTrack), "focused");
       context.AddBool( trk->GetSelected(), "selected" );
       //JKC: Possibly add later...
-      //context.AddItem( GetTrackView::Get( *trk ).GetHeight(), "height" );
+      //context.AddItem( TrackView::Get( *trk ).GetHeight(), "height" );
       trk->TypeSwitch( [&] (const WaveTrack* t ) {
          float vzmin, vzmax;
          t->GetDisplayBounds(&vzmin, &vzmax);
diff --git a/src/menus/ViewMenus.cpp b/src/menus/ViewMenus.cpp
index 4c8e8e8a6..e311aaebd 100644
--- a/src/menus/ViewMenus.cpp
+++ b/src/menus/ViewMenus.cpp
@@ -206,10 +206,9 @@ void DoZoomFitV(AudacityProject &project)
    height -= 28;
    
    // The height of minimized and non-audio tracks cannot be apportioned
-   const auto GetHeight = []( const Track *track )
-      { return TrackView::Get( *track ).GetHeight(); };
    height -=
-      tracks.Any().sum( GetHeight ) - range.sum( GetHeight );
+      tracks.Any().sum( TrackView::GetTrackHeight )
+         - range.sum( TrackView::GetTrackHeight );
    
    // Give each resized track the average of the remaining height
    height = height / count;
diff --git a/src/tracks/ui/TrackSelectHandle.cpp b/src/tracks/ui/TrackSelectHandle.cpp
index 63738bc54..3761b3de9 100644
--- a/src/tracks/ui/TrackSelectHandle.cpp
+++ b/src/tracks/ui/TrackSelectHandle.cpp
@@ -11,6 +11,7 @@ Paul Licameli split from TrackPanel.cpp
 #include "../../Audacity.h"
 #include "TrackSelectHandle.h"
 
+#include "TrackView.h"
 #include "../../Menus.h"
 #include "../../Project.h"
 #include "../../ProjectAudioIO.h"
@@ -219,7 +220,7 @@ void TrackSelectHandle::CalculateRearrangingThresholds(const wxMouseEvent & even
    if (tracks.CanMoveUp(mpTrack.get()))
       mMoveUpThreshold =
          event.m_y -
-            tracks.GetGroupHeight(
+            TrackView::GetChannelGroupHeight(
                * -- tracks.FindLeader( mpTrack.get() ) );
    else
       mMoveUpThreshold = INT_MIN;
@@ -227,7 +228,7 @@ void TrackSelectHandle::CalculateRearrangingThresholds(const wxMouseEvent & even
    if (tracks.CanMoveDown(mpTrack.get()))
       mMoveDownThreshold =
          event.m_y +
-            tracks.GetGroupHeight(
+            TrackView::GetChannelGroupHeight(
                * ++ tracks.FindLeader( mpTrack.get() ) );
    else
       mMoveDownThreshold = INT_MAX;
diff --git a/src/tracks/ui/TrackView.cpp b/src/tracks/ui/TrackView.cpp
index 843fdee4f..bdf9ae3dd 100644
--- a/src/tracks/ui/TrackView.cpp
+++ b/src/tracks/ui/TrackView.cpp
@@ -18,6 +18,29 @@ TrackView::~TrackView()
 {
 }
 
+int TrackView::GetTrackHeight( const Track *pTrack )
+{
+   return pTrack ? Get( *pTrack ).GetHeight() : 0;
+}
+
+int TrackView::GetChannelGroupHeight( const Track *pTrack )
+{
+   return pTrack ? TrackList::Channels( pTrack ).sum( GetTrackHeight ) : 0;
+}
+
+int TrackView::GetCumulativeHeight( const Track *pTrack )
+{
+   if ( !pTrack )
+      return 0;
+   auto &view = Get( *pTrack );
+   return view.GetY() + view.GetHeight();
+}
+
+int TrackView::GetTotalHeight( const TrackList &list )
+{
+   return GetCumulativeHeight( *list.Any().rbegin() );
+}
+
 void TrackView::Copy( const TrackView &other )
 {
    mMinimized = other.mMinimized;
diff --git a/src/tracks/ui/TrackView.h b/src/tracks/ui/TrackView.h
index 5fa4a564b..e1afaa32d 100644
--- a/src/tracks/ui/TrackView.h
+++ b/src/tracks/ui/TrackView.h
@@ -15,6 +15,7 @@ Paul Licameli split from class Track
 #include "CommonTrackPanelCell.h" // to inherit
 
 class Track;
+class TrackList;
 class TrackVRulerControls;
 class TrackPanelResizerCell;
 
@@ -32,6 +33,14 @@ public:
       : CommonTrackCell{ pTrack } {}
    virtual ~TrackView() = 0;
 
+   // some static conveniences, useful for summation over track iterator
+   // ranges
+   static int GetTrackHeight( const Track *pTrack );
+   static int GetChannelGroupHeight( const Track *pTrack );
+   // Total height of the given track and all previous ones (constant time!)
+   static int GetCumulativeHeight( const Track *pTrack );
+   static int GetTotalHeight( const TrackList &list );
+
    // Copy view state, for undo/redo purposes
    virtual void Copy( const TrackView &other );
 

From 278509a5054e07e0eccabece9c3c471c3aef9bc4 Mon Sep 17 00:00:00 2001
From: Paul Licameli <paul.licameli@audacityteam.org>
Date: Sat, 22 Jun 2019 10:13:31 -0400
Subject: [PATCH 2/6] TrackView, not TrackList, updates Y coordinates of views,
 using events

---
 src/Track.cpp               | 51 ++++++++++++++++++++++------------
 src/Track.h                 |  8 ++++--
 src/tracks/ui/TrackView.cpp | 55 ++++++++++++++++++++++++++++++++++++-
 3 files changed, 92 insertions(+), 22 deletions(-)

diff --git a/src/Track.cpp b/src/Track.cpp
index 4b9fae1fd..4778b1d70 100644
--- a/src/Track.cpp
+++ b/src/Track.cpp
@@ -156,7 +156,6 @@ void Track::SetLinked(bool l)
    if (pList && !pList->mPendingUpdates.empty()) {
       auto orig = pList->FindById( GetId() );
       if (orig && orig != this) {
-         // delegate, and rely on RecalcPositions to copy back
          orig->SetLinked(l);
          return;
       }
@@ -532,23 +531,17 @@ void TrackList::RecalcPositions(TrackNodePointer node)
 
    Track *t;
    int i = 0;
-   int y = 0;
 
    auto prev = getPrev( node );
    if ( !isNull( prev ) ) {
       t = prev.first->get();
       i = t->GetIndex() + 1;
-      auto &view = TrackView::Get( *t );
-      y = view.GetY() + view.GetHeight();
    }
 
    const auto theEnd = end();
    for (auto n = Find( node.first->get() ); n != theEnd; ++n) {
       t = *n;
-      auto &view = TrackView::Get( *t );
       t->SetIndex(i++);
-      view.SetY(y);
-      y += view.GetHeight();
    }
 
    UpdatePendingTracks();
@@ -568,16 +561,21 @@ void TrackList::DataEvent( const std::shared_ptr<Track> &pTrack, int code )
       safenew TrackListEvent{ EVT_TRACKLIST_TRACK_DATA_CHANGE, pTrack, code } );
 }
 
-void TrackList::PermutationEvent()
+void TrackList::PermutationEvent(TrackNodePointer node)
 {
    // wxWidgets will own the event object
-   QueueEvent( safenew TrackListEvent{ EVT_TRACKLIST_PERMUTED } );
+   QueueEvent( safenew TrackListEvent{ EVT_TRACKLIST_PERMUTED, *node.first } );
 }
 
-void TrackList::DeletionEvent()
+void TrackList::DeletionEvent(TrackNodePointer node)
 {
    // wxWidgets will own the event object
-   QueueEvent( safenew TrackListEvent{ EVT_TRACKLIST_DELETION } );
+   QueueEvent( safenew TrackListEvent{
+      EVT_TRACKLIST_DELETION,
+      node.second && node.first != node.second->end()
+         ? *node.first
+         : nullptr
+   } );
 }
 
 void TrackList::AdditionEvent(TrackNodePointer node)
@@ -631,7 +629,7 @@ void TrackList::Permute(const std::vector<TrackNodePointer> &permutation)
    }
    auto n = getBegin();
    RecalcPositions(n);
-   PermutationEvent();
+   PermutationEvent(n);
 }
 
 Track *TrackList::FindById( TrackId id )
@@ -738,7 +736,7 @@ auto TrackList::Replace(Track * t, const ListOfTracks::value_type &with) ->
       pTrack->SetId( t->GetId() );
       RecalcPositions(node);
 
-      DeletionEvent();
+      DeletionEvent(node);
       AdditionEvent(node);
    }
    return holder;
@@ -759,7 +757,7 @@ TrackNodePointer TrackList::Remove(Track *t)
          if ( !isNull( result ) )
             RecalcPositions(result);
 
-         DeletionEvent();
+         DeletionEvent(result);
       }
    }
    return result;
@@ -912,7 +910,7 @@ void TrackList::SwapNodes(TrackNodePointer s1, TrackNodePointer s2)
 
    // Now correct the Index in the tracks, and other things
    RecalcPositions(s1);
-   PermutationEvent();
+   PermutationEvent(s1);
 }
 
 bool TrackList::MoveUp(Track * t)
@@ -1051,6 +1049,11 @@ void TrackList::ClearPendingTracks( ListOfTracks *pAdded )
    if (pAdded)
       pAdded->clear();
 
+   // To find the first node that remains after the first deleted one
+   TrackNodePointer node;
+   bool findingNode = false;
+   bool foundNode = false;
+
    for (auto it = ListOfTracks::begin(), stop = ListOfTracks::end();
         it != stop;) {
       if (it->get()->GetId() == TrackId{}) {
@@ -1058,13 +1061,23 @@ void TrackList::ClearPendingTracks( ListOfTracks *pAdded )
             pAdded->push_back( *it );
          (*it)->SetOwner( {}, {} );
          it = erase( it );
+
+         if (!findingNode)
+            findingNode = true;
+         if (!foundNode && it != stop)
+            node = (*it)->GetNode();
       }
-      else
+      else {
+         if ( findingNode )
+            foundNode = true;
          ++it;
+      }
    }
 
-   if (!empty())
+   if (!empty()) {
       RecalcPositions(getBegin());
+      DeletionEvent( node );
+   }
 }
 
 bool TrackList::ApplyPendingTracks()
@@ -1125,7 +1138,9 @@ bool TrackList::ApplyPendingTracks()
       }
    }
    if (inserted) {
-      RecalcPositions({first, this});
+      TrackNodePointer node{first, this};
+      RecalcPositions(node);
+      AdditionEvent(node);
       result = true;
    }
 
diff --git a/src/Track.h b/src/Track.h
index 321124153..7675fd3bc 100644
--- a/src/Track.h
+++ b/src/Track.h
@@ -1092,6 +1092,7 @@ wxDECLARE_EXPORTED_EVENT(AUDACITY_DLL_API,
                          EVT_TRACKLIST_TRACK_DATA_CHANGE, TrackListEvent);
 
 // Posted when tracks are reordered but otherwise unchanged.
+// mpTrack points to the moved track that is earliest in the New ordering.
 wxDECLARE_EXPORTED_EVENT(AUDACITY_DLL_API,
                          EVT_TRACKLIST_PERMUTED, TrackListEvent);
 
@@ -1105,7 +1106,8 @@ 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
+// Also posted when one track replaces another.
+// mpTrack points to the first track after the deletion, if there is one.
 wxDECLARE_EXPORTED_EVENT(AUDACITY_DLL_API,
                          EVT_TRACKLIST_DELETION, TrackListEvent);
 
@@ -1487,9 +1489,9 @@ private:
 
    void RecalcPositions(TrackNodePointer node);
    void SelectionEvent( const std::shared_ptr<Track> &pTrack );
-   void PermutationEvent();
+   void PermutationEvent(TrackNodePointer node);
    void DataEvent( const std::shared_ptr<Track> &pTrack, int code );
-   void DeletionEvent();
+   void DeletionEvent(TrackNodePointer node = {});
    void AdditionEvent(TrackNodePointer node);
    void ResizingEvent(TrackNodePointer node);
 
diff --git a/src/tracks/ui/TrackView.cpp b/src/tracks/ui/TrackView.cpp
index bdf9ae3dd..d1924434f 100644
--- a/src/tracks/ui/TrackView.cpp
+++ b/src/tracks/ui/TrackView.cpp
@@ -14,6 +14,9 @@ Paul Licameli split from TrackPanel.cpp
 #include "TrackControls.h"
 #include "../../TrackPanelResizerCell.h"
 
+#include "../../ClientData.h"
+#include "../../Project.h"
+
 TrackView::~TrackView()
 {
 }
@@ -45,7 +48,7 @@ void TrackView::Copy( const TrackView &other )
 {
    mMinimized = other.mMinimized;
 
-   // Let mY remain 0 -- TrackList::RecalcPositions corrects it later
+   // Let mY remain 0 -- TrackPositioner corrects it later
    mY = 0;
    mHeight = other.mHeight;
 }
@@ -152,3 +155,53 @@ void TrackView::DoSetHeight(int h)
 {
    mHeight = h;
 }
+
+namespace {
+
+// Attach an object to each project.  It receives track list events and updates
+// track Y coordinates
+struct TrackPositioner : ClientData::Base, wxEvtHandler
+{
+   AudacityProject &mProject;
+
+   explicit TrackPositioner( AudacityProject &project )
+      : mProject{ project }
+   {
+      TrackList::Get( project ).Bind(
+         EVT_TRACKLIST_ADDITION, &TrackPositioner::OnUpdate, this );
+      TrackList::Get( project ).Bind(
+         EVT_TRACKLIST_DELETION, &TrackPositioner::OnUpdate, this );
+      TrackList::Get( project ).Bind(
+         EVT_TRACKLIST_PERMUTED, &TrackPositioner::OnUpdate, this );
+      TrackList::Get( project ).Bind(
+         EVT_TRACKLIST_RESIZING, &TrackPositioner::OnUpdate, this );
+   }
+
+   void OnUpdate( TrackListEvent & e )
+   {
+      e.Skip();
+
+      auto iter =
+         TrackList::Get( mProject ).Find( e.mpTrack.lock().get() );
+      if ( !*iter )
+         return;
+
+      auto prev = iter;
+      auto yy = TrackView::GetCumulativeHeight( *--prev );
+
+      while( auto pTrack = *iter ) {
+         auto &view = TrackView::Get( *pTrack );
+         view.SetY( yy );
+         yy += view.GetHeight();
+         ++iter;
+      }
+   }
+};
+
+static const AudacityProject::AttachedObjects::RegisteredFactory key{
+  []( AudacityProject &project ){
+     return std::make_shared< TrackPositioner >( project );
+   }
+};
+
+}

From 3f1fd8ced0fb5fe617ad2dd7808cd1ae2ca2c0f3 Mon Sep 17 00:00:00 2001
From: Paul Licameli <paul.licameli@audacityteam.org>
Date: Sat, 22 Jun 2019 10:27:04 -0400
Subject: [PATCH 3/6] TrackView handles its own special XML attributes via
 virtual functions

---
 src/Track.cpp                          | 23 +++++++++--------------
 src/tracks/ui/CommonTrackPanelCell.cpp |  9 +++++++++
 src/tracks/ui/CommonTrackPanelCell.h   |  7 +++++++
 src/tracks/ui/TrackView.cpp            | 26 ++++++++++++++++++++++++++
 src/tracks/ui/TrackView.h              |  3 +++
 5 files changed, 54 insertions(+), 14 deletions(-)

diff --git a/src/Track.cpp b/src/Track.cpp
index 4778b1d70..6e77df7f9 100644
--- a/src/Track.cpp
+++ b/src/Track.cpp
@@ -1191,9 +1191,10 @@ void Track::WriteCommonXMLAttributes(
       xmlFile.WriteAttr(wxT("name"), GetName());
       xmlFile.WriteAttr(wxT("isSelected"), this->GetSelected());
    }
-   auto &view = TrackView::Get( *this );
-   xmlFile.WriteAttr(wxT("height"), view.GetActualHeight());
-   xmlFile.WriteAttr(wxT("minimized"), view.GetMinimized());
+   if ( mpView )
+      mpView->WriteXMLAttributes( xmlFile );
+   if ( mpControls )
+      mpControls->WriteXMLAttributes( xmlFile );
 }
 
 // Return true iff the attribute is recognized.
@@ -1201,21 +1202,15 @@ bool Track::HandleCommonXMLAttribute(const wxChar *attr, const wxChar *value)
 {
    long nValue = -1;
    wxString strValue( value );
-   if (!wxStrcmp(attr, wxT("name")) &&
+   if ( mpView && mpView->HandleXMLAttribute( attr, value ) )
+      ;
+   else if ( mpControls && mpControls->HandleXMLAttribute( attr, value ) )
+      ;
+   else if (!wxStrcmp(attr, wxT("name")) &&
       XMLValueChecker::IsGoodString(strValue)) {
       SetName( strValue );
       return true;
    }
-   else if (!wxStrcmp(attr, wxT("height")) &&
-         XMLValueChecker::IsGoodInt(strValue) && strValue.ToLong(&nValue)) {
-      TrackView::Get( *this ).SetHeight(nValue);
-      return true;
-   }
-   else if (!wxStrcmp(attr, wxT("minimized")) &&
-         XMLValueChecker::IsGoodInt(strValue) && strValue.ToLong(&nValue)) {
-      TrackView::Get( *this ).SetMinimized(nValue != 0);
-      return true;
-   }
    else if (!wxStrcmp(attr, wxT("isSelected")) &&
          XMLValueChecker::IsGoodInt(strValue) && strValue.ToLong(&nValue)) {
       this->SetSelected(nValue != 0);
diff --git a/src/tracks/ui/CommonTrackPanelCell.cpp b/src/tracks/ui/CommonTrackPanelCell.cpp
index 5c3caeb26..e3b280e6f 100644
--- a/src/tracks/ui/CommonTrackPanelCell.cpp
+++ b/src/tracks/ui/CommonTrackPanelCell.cpp
@@ -66,3 +66,12 @@ std::shared_ptr<Track> CommonTrackCell::DoFindTrack()
 {
    return mwTrack.lock();
 }
+
+void CommonTrackCell::WriteXMLAttributes( XMLWriter & ) const
+{
+}
+
+bool CommonTrackCell::HandleXMLAttribute( const wxChar *, const wxChar * )
+{
+   return false;
+}
diff --git a/src/tracks/ui/CommonTrackPanelCell.h b/src/tracks/ui/CommonTrackPanelCell.h
index a571624b5..ace3520fe 100644
--- a/src/tracks/ui/CommonTrackPanelCell.h
+++ b/src/tracks/ui/CommonTrackPanelCell.h
@@ -19,6 +19,7 @@ Paul Licameli split from TrackPanel.cpp
 #include <functional>
 
 class Track;
+class XMLWriter;
 
 class AUDACITY_DLL_API CommonTrackPanelCell /* not final */
    : public TrackPanelCell
@@ -65,6 +66,12 @@ public:
 
    virtual void Reparent( const std::shared_ptr<Track> &parent );
 
+   // default does nothing
+   virtual void WriteXMLAttributes( XMLWriter & ) const;
+
+   // default recognizes no attributes, and returns false
+   virtual bool HandleXMLAttribute( const wxChar *attr, const wxChar *value );
+
 private:
    std::weak_ptr< Track > mwTrack;
 };
diff --git a/src/tracks/ui/TrackView.cpp b/src/tracks/ui/TrackView.cpp
index d1924434f..0deb266c1 100644
--- a/src/tracks/ui/TrackView.cpp
+++ b/src/tracks/ui/TrackView.cpp
@@ -16,6 +16,8 @@ Paul Licameli split from TrackPanel.cpp
 
 #include "../../ClientData.h"
 #include "../../Project.h"
+#include "../../xml/XMLTagHandler.h"
+#include "../../xml/XMLWriter.h"
 
 TrackView::~TrackView()
 {
@@ -74,6 +76,30 @@ void TrackView::SetMinimized(bool isMinimized)
       leader->AdjustPositions();
 }
 
+void TrackView::WriteXMLAttributes( XMLWriter &xmlFile ) const
+{
+   xmlFile.WriteAttr(wxT("height"), GetActualHeight());
+   xmlFile.WriteAttr(wxT("minimized"), GetMinimized());
+}
+
+bool TrackView::HandleXMLAttribute( const wxChar *attr, const wxChar *value )
+{
+   wxString strValue;
+   long nValue;
+   if (!wxStrcmp(attr, wxT("height")) &&
+         XMLValueChecker::IsGoodInt(strValue) && strValue.ToLong(&nValue)) {
+      SetHeight(nValue);
+      return true;
+   }
+   else if (!wxStrcmp(attr, wxT("minimized")) &&
+         XMLValueChecker::IsGoodInt(strValue) && strValue.ToLong(&nValue)) {
+      SetMinimized(nValue != 0);
+      return true;
+   }
+   else
+      return false;
+}
+
 void TrackView::DoSetMinimized(bool isMinimized)
 {
    mMinimized = isMinimized;
diff --git a/src/tracks/ui/TrackView.h b/src/tracks/ui/TrackView.h
index e1afaa32d..3c339c78b 100644
--- a/src/tracks/ui/TrackView.h
+++ b/src/tracks/ui/TrackView.h
@@ -69,6 +69,9 @@ public:
    std::shared_ptr<TrackPanelCell> GetResizer();
    std::shared_ptr<const TrackPanelCell> GetResizer() const;
 
+   void WriteXMLAttributes( XMLWriter & ) const override;
+   bool HandleXMLAttribute( const wxChar *attr, const wxChar *value ) override;
+
 protected:
    virtual void DoSetMinimized( bool isMinimized );
 

From 8793d6b475fad20c2dad3832e98241a7b2315cc3 Mon Sep 17 00:00:00 2001
From: Paul Licameli <paul.licameli@audacityteam.org>
Date: Sat, 22 Jun 2019 10:43:55 -0400
Subject: [PATCH 4/6] Demote Copy to CommonTrackCell; Track points only to that
 base class

---
 src/Track.h                                 |  6 +++---
 src/tracks/labeltrack/ui/LabelTrackView.cpp |  2 +-
 src/tracks/labeltrack/ui/LabelTrackView.h   |  2 +-
 src/tracks/ui/CommonTrackPanelCell.cpp      |  4 ++++
 src/tracks/ui/CommonTrackPanelCell.h        |  3 +++
 src/tracks/ui/TrackView.cpp                 | 15 ++++++++++-----
 src/tracks/ui/TrackView.h                   |  2 +-
 7 files changed, 23 insertions(+), 11 deletions(-)

diff --git a/src/Track.h b/src/Track.h
index 7675fd3bc..edc82f986 100644
--- a/src/Track.h
+++ b/src/Track.h
@@ -263,8 +263,8 @@ class AUDACITY_DLL_API Track /* not final */
 
    // Return another, associated TrackPanelCell object that implements
    // click and drag and keystrokes in the track contents.
-   std::shared_ptr<TrackView> GetTrackView();
-   std::shared_ptr<const TrackView> GetTrackView() const;
+   std::shared_ptr<CommonTrackCell> GetTrackView();
+   std::shared_ptr<const CommonTrackCell> GetTrackView() const;
 
    // Return another, associated TrackPanelCell object that implements the
    // drop-down, close and minimize buttons, etc.
@@ -704,7 +704,7 @@ public:
    bool HandleCommonXMLAttribute(const wxChar *attr, const wxChar *value);
 
 protected:
-   std::shared_ptr<TrackView> mpView;
+   std::shared_ptr<CommonTrackCell> mpView;
    std::shared_ptr<CommonTrackCell> mpControls;
 };
 
diff --git a/src/tracks/labeltrack/ui/LabelTrackView.cpp b/src/tracks/labeltrack/ui/LabelTrackView.cpp
index 620a22e87..2550ed99b 100644
--- a/src/tracks/labeltrack/ui/LabelTrackView.cpp
+++ b/src/tracks/labeltrack/ui/LabelTrackView.cpp
@@ -97,7 +97,7 @@ void LabelTrackView::UnbindFrom( LabelTrack *pParent )
       EVT_LABELTRACK_PERMUTED, &LabelTrackView::OnLabelPermuted, this );
 }
 
-void LabelTrackView::Copy( const TrackView &other )
+void LabelTrackView::Copy( const CommonTrackCell &other )
 {
    TrackView::Copy( other );
 
diff --git a/src/tracks/labeltrack/ui/LabelTrackView.h b/src/tracks/labeltrack/ui/LabelTrackView.h
index 4a25aabb7..dbcb631cb 100644
--- a/src/tracks/labeltrack/ui/LabelTrackView.h
+++ b/src/tracks/labeltrack/ui/LabelTrackView.h
@@ -82,7 +82,7 @@ private:
    std::shared_ptr<TrackVRulerControls> DoGetVRulerControls() override;
 
    // Preserve some view state too for undo/redo purposes
-   void Copy( const TrackView &other ) override;
+   void Copy( const CommonTrackCell &other ) override;
 
 public:
    static void DoEditLabels(
diff --git a/src/tracks/ui/CommonTrackPanelCell.cpp b/src/tracks/ui/CommonTrackPanelCell.cpp
index e3b280e6f..e0ac5ff8f 100644
--- a/src/tracks/ui/CommonTrackPanelCell.cpp
+++ b/src/tracks/ui/CommonTrackPanelCell.cpp
@@ -57,6 +57,10 @@ CommonTrackCell::CommonTrackCell( const std::shared_ptr< Track > &parent )
 
 CommonTrackCell::~CommonTrackCell() = default;
 
+void CommonTrackCell::Copy( const CommonTrackCell & )
+{
+}
+
 void CommonTrackCell::Reparent( const std::shared_ptr<Track> &parent )
 {
    mwTrack = parent;
diff --git a/src/tracks/ui/CommonTrackPanelCell.h b/src/tracks/ui/CommonTrackPanelCell.h
index ace3520fe..a2db5d54d 100644
--- a/src/tracks/ui/CommonTrackPanelCell.h
+++ b/src/tracks/ui/CommonTrackPanelCell.h
@@ -62,6 +62,9 @@ public:
 
   ~CommonTrackCell();
 
+   // Copy state, for undo/redo purposes
+   virtual void Copy( const CommonTrackCell &other );
+
    std::shared_ptr<Track> DoFindTrack() override;
 
    virtual void Reparent( const std::shared_ptr<Track> &parent );
diff --git a/src/tracks/ui/TrackView.cpp b/src/tracks/ui/TrackView.cpp
index 0deb266c1..7e6080827 100644
--- a/src/tracks/ui/TrackView.cpp
+++ b/src/tracks/ui/TrackView.cpp
@@ -46,8 +46,13 @@ int TrackView::GetTotalHeight( const TrackList &list )
    return GetCumulativeHeight( *list.Any().rbegin() );
 }
 
-void TrackView::Copy( const TrackView &other )
+void TrackView::Copy( const CommonTrackCell &otherCell )
 {
+   auto pOther = dynamic_cast< const TrackView* >( &otherCell );
+   if ( !pOther )
+      return;
+   auto &other = *pOther;
+
    mMinimized = other.mMinimized;
 
    // Let mY remain 0 -- TrackPositioner corrects it later
@@ -57,12 +62,12 @@ void TrackView::Copy( const TrackView &other )
 
 TrackView &TrackView::Get( Track &track )
 {
-   return *track.GetTrackView();
+   return static_cast<TrackView&>( *track.GetTrackView() );
 }
 
 const TrackView &TrackView::Get( const Track &track )
 {
-   return *track.GetTrackView();
+   return static_cast<const TrackView&>( *track.GetTrackView() );
 }
 
 void TrackView::SetMinimized(bool isMinimized)
@@ -105,7 +110,7 @@ void TrackView::DoSetMinimized(bool isMinimized)
    mMinimized = isMinimized;
 }
 
-std::shared_ptr<TrackView> Track::GetTrackView()
+std::shared_ptr<CommonTrackCell> Track::GetTrackView()
 {
    if (!mpView)
       // create on demand
@@ -113,7 +118,7 @@ std::shared_ptr<TrackView> Track::GetTrackView()
    return mpView;
 }
 
-std::shared_ptr<const TrackView> Track::GetTrackView() const
+std::shared_ptr<const CommonTrackCell> Track::GetTrackView() const
 {
    return const_cast<Track*>(this)->GetTrackView();
 }
diff --git a/src/tracks/ui/TrackView.h b/src/tracks/ui/TrackView.h
index 3c339c78b..0a57decae 100644
--- a/src/tracks/ui/TrackView.h
+++ b/src/tracks/ui/TrackView.h
@@ -42,7 +42,7 @@ public:
    static int GetTotalHeight( const TrackList &list );
 
    // Copy view state, for undo/redo purposes
-   virtual void Copy( const TrackView &other );
+   void Copy( const CommonTrackCell &other ) override;
 
    static TrackView &Get( Track & );
    static const TrackView &Get( const Track & );

From dc9e436dde54381582635dc8c015b3016f805ae4 Mon Sep 17 00:00:00 2001
From: Paul Licameli <paul.licameli@audacityteam.org>
Date: Sat, 22 Jun 2019 11:02:55 -0400
Subject: [PATCH 5/6] Change the track view copy function...

... It is const, renamed CopyTo, and invokes the create-on-demand factory in
the destination track; this means Track.cpp doesn't need to do that, and so
does not need TrackView.h
---
 src/Track.cpp                               |  4 +---
 src/tracks/labeltrack/ui/LabelTrackView.cpp |  7 ++++---
 src/tracks/labeltrack/ui/LabelTrackView.h   |  2 +-
 src/tracks/ui/CommonTrackPanelCell.cpp      |  2 +-
 src/tracks/ui/CommonTrackPanelCell.h        |  3 ++-
 src/tracks/ui/TrackView.cpp                 | 13 +++++--------
 src/tracks/ui/TrackView.h                   |  2 +-
 7 files changed, 15 insertions(+), 18 deletions(-)

diff --git a/src/Track.cpp b/src/Track.cpp
index 6e77df7f9..e3a78a8d4 100644
--- a/src/Track.cpp
+++ b/src/Track.cpp
@@ -41,8 +41,6 @@ and TimeTrack.
 
 #include "InconsistencyException.h"
 
-#include "tracks/ui/TrackView.h"
-
 #ifdef _MSC_VER
 //Disable truncation warnings
 #pragma warning( disable : 4786 )
@@ -115,7 +113,7 @@ Track::Holder Track::Duplicate() const
 
    if (mpView)
       // Copy view state that might be important to undo/redo
-      TrackView::Get( *result ).Copy( *mpView );
+      mpView->CopyTo( *result );
 
    return result;
 }
diff --git a/src/tracks/labeltrack/ui/LabelTrackView.cpp b/src/tracks/labeltrack/ui/LabelTrackView.cpp
index 2550ed99b..12c75c127 100644
--- a/src/tracks/labeltrack/ui/LabelTrackView.cpp
+++ b/src/tracks/labeltrack/ui/LabelTrackView.cpp
@@ -97,13 +97,14 @@ void LabelTrackView::UnbindFrom( LabelTrack *pParent )
       EVT_LABELTRACK_PERMUTED, &LabelTrackView::OnLabelPermuted, this );
 }
 
-void LabelTrackView::Copy( const CommonTrackCell &other )
+void LabelTrackView::CopyTo( Track &track ) const
 {
-   TrackView::Copy( other );
+   TrackView::CopyTo( track );
+   auto &other = TrackView::Get( track );
 
    if ( const auto pOther = dynamic_cast< const LabelTrackView* >( &other ) ) {
       // only one field is important to preserve in undo/redo history
-      mSelIndex = pOther->mSelIndex;
+      pOther->mSelIndex = mSelIndex;
    }
 }
 
diff --git a/src/tracks/labeltrack/ui/LabelTrackView.h b/src/tracks/labeltrack/ui/LabelTrackView.h
index dbcb631cb..39376d28d 100644
--- a/src/tracks/labeltrack/ui/LabelTrackView.h
+++ b/src/tracks/labeltrack/ui/LabelTrackView.h
@@ -82,7 +82,7 @@ private:
    std::shared_ptr<TrackVRulerControls> DoGetVRulerControls() override;
 
    // Preserve some view state too for undo/redo purposes
-   void Copy( const CommonTrackCell &other ) override;
+   void CopyTo( Track &track ) const override;
 
 public:
    static void DoEditLabels(
diff --git a/src/tracks/ui/CommonTrackPanelCell.cpp b/src/tracks/ui/CommonTrackPanelCell.cpp
index e0ac5ff8f..f34fafe78 100644
--- a/src/tracks/ui/CommonTrackPanelCell.cpp
+++ b/src/tracks/ui/CommonTrackPanelCell.cpp
@@ -57,7 +57,7 @@ CommonTrackCell::CommonTrackCell( const std::shared_ptr< Track > &parent )
 
 CommonTrackCell::~CommonTrackCell() = default;
 
-void CommonTrackCell::Copy( const CommonTrackCell & )
+void CommonTrackCell::CopyTo( Track& ) const
 {
 }
 
diff --git a/src/tracks/ui/CommonTrackPanelCell.h b/src/tracks/ui/CommonTrackPanelCell.h
index a2db5d54d..b229a4c60 100644
--- a/src/tracks/ui/CommonTrackPanelCell.h
+++ b/src/tracks/ui/CommonTrackPanelCell.h
@@ -63,7 +63,8 @@ public:
   ~CommonTrackCell();
 
    // Copy state, for undo/redo purposes
-   virtual void Copy( const CommonTrackCell &other );
+   // The default does nothing
+   virtual void CopyTo( Track &track ) const;
 
    std::shared_ptr<Track> DoFindTrack() override;
 
diff --git a/src/tracks/ui/TrackView.cpp b/src/tracks/ui/TrackView.cpp
index 7e6080827..47524c25f 100644
--- a/src/tracks/ui/TrackView.cpp
+++ b/src/tracks/ui/TrackView.cpp
@@ -46,18 +46,15 @@ int TrackView::GetTotalHeight( const TrackList &list )
    return GetCumulativeHeight( *list.Any().rbegin() );
 }
 
-void TrackView::Copy( const CommonTrackCell &otherCell )
+void TrackView::CopyTo( Track &track ) const
 {
-   auto pOther = dynamic_cast< const TrackView* >( &otherCell );
-   if ( !pOther )
-      return;
-   auto &other = *pOther;
+   auto &other = Get( track );
 
-   mMinimized = other.mMinimized;
+   other.mMinimized = mMinimized;
 
    // Let mY remain 0 -- TrackPositioner corrects it later
-   mY = 0;
-   mHeight = other.mHeight;
+   other.mY = 0;
+   other.mHeight = mHeight;
 }
 
 TrackView &TrackView::Get( Track &track )
diff --git a/src/tracks/ui/TrackView.h b/src/tracks/ui/TrackView.h
index 0a57decae..0feee6c35 100644
--- a/src/tracks/ui/TrackView.h
+++ b/src/tracks/ui/TrackView.h
@@ -42,7 +42,7 @@ public:
    static int GetTotalHeight( const TrackList &list );
 
    // Copy view state, for undo/redo purposes
-   void Copy( const CommonTrackCell &other ) override;
+   void CopyTo( Track &track ) const override;
 
    static TrackView &Get( Track & );
    static const TrackView &Get( const Track & );

From 9e731390f65e5c810ea5563df432195a956bca7a Mon Sep 17 00:00:00 2001
From: Paul Licameli <paul.licameli@audacityteam.org>
Date: Sat, 22 Jun 2019 11:27:54 -0400
Subject: [PATCH 6/6] Don't define any Track members outside of Track.cpp

---
 src/Track.cpp                   | 30 ++++++++++++++++---------
 src/Track.h                     | 36 +++++++-----------------------
 src/tracks/ui/TrackControls.cpp | 13 +++++++++--
 src/tracks/ui/TrackControls.h   | 11 ++++++++++
 src/tracks/ui/TrackView.cpp     | 39 ++++++++++-----------------------
 src/tracks/ui/TrackView.h       | 11 ++++++++++
 6 files changed, 72 insertions(+), 68 deletions(-)

diff --git a/src/Track.cpp b/src/Track.cpp
index e3a78a8d4..9a4d50cd3 100644
--- a/src/Track.cpp
+++ b/src/Track.cpp
@@ -138,6 +138,26 @@ void Track::SetOwner
    mNode = node;
 }
 
+const std::shared_ptr<CommonTrackCell> &Track::GetTrackView()
+{
+   return mpView;
+}
+
+void Track::SetTrackView( const std::shared_ptr<CommonTrackCell> &pView )
+{
+   mpView = pView;
+}
+
+const std::shared_ptr<CommonTrackCell> &Track::GetTrackControls()
+{
+   return mpControls;
+}
+
+void Track::SetTrackControls( const std::shared_ptr<CommonTrackCell> &pControls )
+{
+   mpControls = pControls;
+}
+
 int Track::GetIndex() const
 {
    return mIndex;
@@ -1270,13 +1290,3 @@ void TrackFactory::Destroy( AudacityProject &project )
 {
    project.AttachedObjects::Assign( key2, nullptr );
 }
-
-template<> auto DoGetControls::Implementation() -> Function {
-   return nullptr;
-}
-static DoGetControls registerDoGetControls;
-
-template<> auto DoGetView::Implementation() -> Function {
-   return nullptr;
-}
-static DoGetView registerDoGetView;
diff --git a/src/Track.h b/src/Track.h
index edc82f986..d850a983a 100644
--- a/src/Track.h
+++ b/src/Track.h
@@ -261,15 +261,15 @@ class AUDACITY_DLL_API Track /* not final */
  public:
    mutable wxSize vrulerSize;
 
-   // Return another, associated TrackPanelCell object that implements
-   // click and drag and keystrokes in the track contents.
-   std::shared_ptr<CommonTrackCell> GetTrackView();
-   std::shared_ptr<const CommonTrackCell> GetTrackView() const;
+   // These are exposed only for the purposes of the TrackView class, to
+   // initialize the pointer on demand
+   const std::shared_ptr<CommonTrackCell> &GetTrackView();
+   void SetTrackView( const std::shared_ptr<CommonTrackCell> &pView );
 
-   // Return another, associated TrackPanelCell object that implements the
-   // drop-down, close and minimize buttons, etc.
-   std::shared_ptr<TrackPanelCell> GetTrackControls();
-   std::shared_ptr<const TrackPanelCell> GetTrackControls() const;
+   // These are exposed only for the purposes of the TrackControls class, to
+   // initialize the pointer on demand
+   const std::shared_ptr<CommonTrackCell> &GetTrackControls();
+   void SetTrackControls( const std::shared_ptr<CommonTrackCell> &pControls );
 
    // Return another, associated TrackPanelCell object that implements the
 
@@ -1588,24 +1588,4 @@ class AUDACITY_DLL_API TrackFactory final
 #endif
 };
 
-#include "AttachedVirtualFunction.h"
-
-struct DoGetControlsTag;
-
-using DoGetControls =
-AttachedVirtualFunction<
-   DoGetControlsTag,
-   std::shared_ptr< TrackControls >,
-   Track
->;
-
-struct DoGetViewTag;
-
-using DoGetView =
-AttachedVirtualFunction<
-   DoGetViewTag,
-   std::shared_ptr< TrackView >,
-   Track
->;
-
 #endif
diff --git a/src/tracks/ui/TrackControls.cpp b/src/tracks/ui/TrackControls.cpp
index 0c850ec59..5e4dee257 100644
--- a/src/tracks/ui/TrackControls.cpp
+++ b/src/tracks/ui/TrackControls.cpp
@@ -24,11 +24,20 @@ TrackControls::~TrackControls()
 
 TrackControls &TrackControls::Get( Track &track )
 {
-   return *static_cast<TrackControls*>( track.GetTrackControls().get() );
+   auto pControls =
+      std::static_pointer_cast<TrackControls>( track.GetTrackControls() );
+   if (!pControls)
+      // create on demand
+      track.SetTrackControls( pControls = DoGetControls::Call( track ) );
+   return *pControls;
 }
 
 const TrackControls &TrackControls::Get( const Track &track )
 {
-   return *static_cast<const TrackControls*>( track.GetTrackControls().get() );
+   return Get( const_cast< Track& >( track ) );
 }
 
+template<> auto DoGetControls::Implementation() -> Function {
+   return nullptr;
+}
+static DoGetControls registerDoGetControls;
diff --git a/src/tracks/ui/TrackControls.h b/src/tracks/ui/TrackControls.h
index 317548343..11f451bc6 100644
--- a/src/tracks/ui/TrackControls.h
+++ b/src/tracks/ui/TrackControls.h
@@ -28,4 +28,15 @@ public:
    virtual ~TrackControls() = 0;
 };
 
+#include "AttachedVirtualFunction.h"
+
+struct DoGetControlsTag;
+
+using DoGetControls =
+AttachedVirtualFunction<
+   DoGetControlsTag,
+   std::shared_ptr< TrackControls >,
+   Track
+>;
+
 #endif
diff --git a/src/tracks/ui/TrackView.cpp b/src/tracks/ui/TrackView.cpp
index 47524c25f..7d25afe14 100644
--- a/src/tracks/ui/TrackView.cpp
+++ b/src/tracks/ui/TrackView.cpp
@@ -59,12 +59,16 @@ void TrackView::CopyTo( Track &track ) const
 
 TrackView &TrackView::Get( Track &track )
 {
-   return static_cast<TrackView&>( *track.GetTrackView() );
+   auto pView = std::static_pointer_cast<TrackView>( track.GetTrackView() );
+   if (!pView)
+      // create on demand
+      track.SetTrackView( pView = DoGetView::Call( track ) );
+   return *pView;
 }
 
 const TrackView &TrackView::Get( const Track &track )
 {
-   return static_cast<const TrackView&>( *track.GetTrackView() );
+   return Get( const_cast< Track& >( track ) );
 }
 
 void TrackView::SetMinimized(bool isMinimized)
@@ -107,32 +111,6 @@ void TrackView::DoSetMinimized(bool isMinimized)
    mMinimized = isMinimized;
 }
 
-std::shared_ptr<CommonTrackCell> Track::GetTrackView()
-{
-   if (!mpView)
-      // create on demand
-      mpView = DoGetView::Call( *this );
-   return mpView;
-}
-
-std::shared_ptr<const CommonTrackCell> Track::GetTrackView() const
-{
-   return const_cast<Track*>(this)->GetTrackView();
-}
-
-std::shared_ptr<TrackPanelCell> Track::GetTrackControls()
-{
-   if (!mpControls)
-      // create on demand
-      mpControls = DoGetControls::Call( *this );
-   return mpControls;
-}
-
-std::shared_ptr<const TrackPanelCell> Track::GetTrackControls() const
-{
-   return const_cast< Track* >( this )->GetTrackControls();
-}
-
 std::shared_ptr<TrackVRulerControls> TrackView::GetVRulerControls()
 {
    if (!mpVRulerControls)
@@ -233,3 +211,8 @@ static const AudacityProject::AttachedObjects::RegisteredFactory key{
 };
 
 }
+
+template<> auto DoGetView::Implementation() -> Function {
+   return nullptr;
+}
+static DoGetView registerDoGetView;
diff --git a/src/tracks/ui/TrackView.h b/src/tracks/ui/TrackView.h
index 0feee6c35..fcf855b15 100644
--- a/src/tracks/ui/TrackView.h
+++ b/src/tracks/ui/TrackView.h
@@ -93,4 +93,15 @@ private:
    int            mHeight{ DefaultHeight };
 };
 
+#include "AttachedVirtualFunction.h"
+
+struct DoGetViewTag;
+
+using DoGetView =
+AttachedVirtualFunction<
+   DoGetViewTag,
+   std::shared_ptr< TrackView >,
+   Track
+>;
+
 #endif