Break cycle: TrackPanelResizerCell, TrackPanelResizeHandle, TrackView

src/Track.h

@@ -182,8 +182,13 @@ private:
    long mValue;
 };
 
+using AttachedTrackObjects = ClientData::Site<
+   Track, ClientData::Base, ClientData::SkipCopying, std::shared_ptr
+>;
+
 class AUDACITY_DLL_API Track /* not final */
    : public XMLTagHandler
+   , public AttachedTrackObjects
    , public std::enable_shared_from_this<Track> // see SharedPointer()
 {
    friend class TrackList;
@@ -207,6 +212,7 @@ class AUDACITY_DLL_API Track /* not final */
 
  public:
 
+   using AttachedObjects = ::AttachedTrackObjects;
    using ChannelType = XMLValueChecker::ChannelType;
 
    static const auto LeftChannel = XMLValueChecker::LeftChannel;

src/TrackPanel.cpp

@@ -73,6 +73,7 @@ is time to refresh some aspect of the screen.
 #include "RefreshCode.h"
 #include "TrackArtist.h"
 #include "TrackPanelAx.h"
+#include "TrackPanelResizerCell.h"
 #include "WaveTrack.h"
 #ifdef EXPERIMENTAL_MIDI_OUT
 #include "NoteTrack.h"
@@ -1151,7 +1152,7 @@ struct ChannelGroup final : TrackPanelGroup {
             yy += height;
             refinement.emplace_back(
                yy - kSeparatorThickness,
-               TrackView::Get( *channel ).GetResizer() );
+               TrackPanelResizerCell::Get( *channel ).shared_from_this() );
          }
       }
 
@@ -1270,8 +1271,9 @@ struct ResizingChannelGroup final : TrackPanelGroup {
       { rect.GetTop(),
          std::make_shared< LabeledChannelGroup >( mpTrack, mLeftOffset ) },
       { rect.GetTop() + rect.GetHeight() - kSeparatorThickness,
-         TrackView::Get( **TrackList::Channels( mpTrack.get() ).rbegin() )
-            .GetResizer() }
+         TrackPanelResizerCell::Get(
+            **TrackList::Channels( mpTrack.get() ).rbegin() ).shared_from_this()
+      }
    } }; }
    std::shared_ptr< Track > mpTrack;
    wxCoord mLeftOffset;

src/TrackPanelResizerCell.cpp

@@ -26,8 +26,8 @@ Paul Licameli split from TrackPanel.cpp
 #include <wx/mousestate.h>
 
 TrackPanelResizerCell::TrackPanelResizerCell(
-   const std::shared_ptr<TrackView> &pView )
-   : mwView{ pView }
+   const std::shared_ptr<Track> &pTrack )
+   : mwTrack{ pTrack }
 {}
 
 std::vector<UIHandlePtr> TrackPanelResizerCell::HitTest
@@ -47,10 +47,7 @@ std::vector<UIHandlePtr> TrackPanelResizerCell::HitTest
 
 std::shared_ptr<Track> TrackPanelResizerCell::DoFindTrack()
 {
-   const auto pView = mwView.lock();
-   if ( pView )
-      return pView->FindTrack();
-   return {};
+   return mwTrack.lock();
 }
 
 void TrackPanelResizerCell::Draw(
@@ -112,3 +109,20 @@ void TrackPanelResizerCell::Draw(
       }
    }
 }
+
+static const AttachedTrackObjects::RegisteredFactory key{
+   []( Track &track ){
+      return std::make_shared<TrackPanelResizerCell>(
+         track.shared_from_this() );
+   }
+};
+
+TrackPanelResizerCell &TrackPanelResizerCell::Get( Track &track )
+{
+   return track.AttachedObjects::Get< TrackPanelResizerCell >( key );
+}
+
+const TrackPanelResizerCell &TrackPanelResizerCell::Get( const Track &track )
+{
+   return Get( const_cast< Track & >( track ) );
+}

src/TrackPanelResizerCell.h

@@ -11,19 +11,26 @@
 #ifndef __AUDACITY_TRACK_PANEL_RESIZER_CELL__
 #define __AUDACITY_TRACK_PANEL_RESIZER_CELL__
 
-#include "tracks/ui/CommonTrackPanelCell.h"
+#include "ClientData.h" // to inherit
+#include "tracks/ui/CommonTrackPanelCell.h" // to inherit
 
+class Track;
 class TrackPanelResizeHandle;
-class TrackView;
 
-class TrackPanelResizerCell : public CommonTrackPanelCell
+class TrackPanelResizerCell
+   : public CommonTrackPanelCell
+   , public std::enable_shared_from_this< TrackPanelResizerCell >
+   , public ClientData::Base
 {
    TrackPanelResizerCell(const TrackPanelResizerCell&) = delete;
    TrackPanelResizerCell &operator= (const TrackPanelResizerCell&) = delete;
 public:
 
+   static TrackPanelResizerCell &Get( Track &track );
+   static const TrackPanelResizerCell &Get( const Track &track );
+
    explicit
-   TrackPanelResizerCell( const std::shared_ptr<TrackView> &pView );
+   TrackPanelResizerCell( const std::shared_ptr<Track> &pTrack );
 
    std::vector<UIHandlePtr> HitTest
       (const TrackPanelMouseState &, const AudacityProject *) override;
@@ -33,7 +40,7 @@ protected:
 
 private:
    // back-pointer is weak to break a cycle
-   std::weak_ptr<TrackView> mwView;
+   std::weak_ptr<Track> mwTrack;
 
    // TrackPanelDrawable implementation
    void Draw(

src/tracks/ui/TrackView.cpp

@@ -12,7 +12,6 @@ Paul Licameli split from TrackPanel.cpp
 #include "../../Track.h"
 
 #include "TrackControls.h"
-#include "../../TrackPanelResizerCell.h"
 
 #include "../../ClientData.h"
 #include "../../Project.h"
@@ -135,20 +134,6 @@ std::shared_ptr<const TrackVRulerControls> TrackView::GetVRulerControls() const
    return const_cast< TrackView* >( this )->GetVRulerControls();
 }
 
-#include "../../TrackPanelResizeHandle.h"
-std::shared_ptr<TrackPanelCell> TrackView::GetResizer()
-{
-   if (!mpResizer)
-      // create on demand
-      mpResizer = std::make_shared<TrackPanelResizerCell>( shared_from_this() );
-   return mpResizer;
-}
-
-std::shared_ptr<const TrackPanelCell> TrackView::GetResizer() const
-{
-   return const_cast<TrackView*>(this)->GetResizer();
-}
-
 void TrackView::DoSetY(int y)
 {
    mY = y;

src/tracks/ui/TrackView.h

@@ -63,11 +63,6 @@ public:
    std::shared_ptr<const TrackVRulerControls> GetVRulerControls() const;
 
 
-   // Return another, associated TrackPanelCell object that implements the
-   // click and drag to resize
-   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;
 
@@ -92,7 +87,6 @@ protected:
    virtual std::shared_ptr<TrackVRulerControls> DoGetVRulerControls() = 0;
 
    std::shared_ptr<TrackVRulerControls> mpVRulerControls;
-   std::shared_ptr<TrackPanelResizerCell> mpResizer;
 
 private:
    bool           mMinimized{ false };