Reimplement Track::Pointer using std::enable_shared_from_this...

... now the Track need not be owned yet by a TrackList

src/Mix.cpp

@@ -85,7 +85,7 @@ void MixAndRender(TrackList *tracks, TrackFactory *trackFactory,
    WaveTrackConstArray waveArray;
 
    for(auto wt : trackRange) {
-      waveArray.push_back( Track::Pointer< const WaveTrack >( wt ) );
+      waveArray.push_back( wt->SharedPointer< const WaveTrack >() );
       tstart = wt->GetStartTime();
       tend = wt->GetEndTime();
       if (tend > mixEndTime)

src/MixerBoard.cpp

@@ -989,7 +989,7 @@ void MixerBoard::UpdateTrackClusters()
 
    for (auto pPlayableTrack: mTracks->Leaders<PlayableTrack>()) {
       // TODO: more-than-two-channels
-      auto spTrack = Track::Pointer<PlayableTrack>( pPlayableTrack );
+      auto spTrack = pPlayableTrack->SharedPointer<PlayableTrack>();
       if (nClusterIndex < nClusterCount)
       {
          // Already showing it.

src/Project.cpp

@@ -4198,7 +4198,7 @@ AudacityProject::AddImportedTracks(const FilePath &fileName,
       auto nChannels = group.size();
       for (auto &uNewTrack : group) {
          auto newTrack = mTracks->Add(std::move(uNewTrack));
-         results.push_back(Track::Pointer(newTrack));
+         results.push_back(newTrack->SharedPointer());
       }
       mTracks->GroupChannels(*first, nChannels);
    }
@@ -4337,7 +4337,7 @@ bool AudacityProject::Import(const FilePath &fileName, WaveTrackArray* pTrackArr
    if (pTrackArray) {
       for (const auto &newTrack : newSharedTracks) {
          newTrack->TypeSwitch( [&](WaveTrack *wt) {
-            pTrackArray->push_back( Track::Pointer< WaveTrack >( wt ) );
+            pTrackArray->push_back( wt->SharedPointer< WaveTrack >() );
          });
       }
    }

src/SelectionState.cpp

@@ -42,7 +42,7 @@ void SelectionState::SelectTrack(
       channel->SetSelected(selected);
 
    if (updateLastPicked)
-      mLastPickedTrack = Track::Pointer( &track );
+      mLastPickedTrack = track.SharedPointer();
 
 //The older code below avoids an anchor on an unselected track.
 
@@ -92,11 +92,11 @@ void SelectionState::ChangeSelectionOnShiftClick
 
       // If our track is at or after the first, extend from the first.
       if( pFirst && track.GetIndex() >= pFirst->GetIndex() )
-         pExtendFrom = Track::Pointer( pFirst );
+         pExtendFrom = pFirst->SharedPointer();
 
       // Our track was earlier than the first.  Extend from the last.
       if( !pExtendFrom )
-         pExtendFrom = Track::Pointer( *trackRange.rbegin() );
+         pExtendFrom = (*trackRange.rbegin())->SharedPointer();
    }
 
    SelectNone( tracks );

src/Track.cpp

@@ -105,7 +105,7 @@ void Track::SetSelected(bool s)
       mSelected = s;
       auto pList = mList.lock();
       if (pList)
-         pList->SelectionEvent( Pointer( this ) );
+         pList->SelectionEvent( SharedPointer() );
    }
 }
 
@@ -351,7 +351,7 @@ void Track::Notify( int code )
 {
    auto pList = mList.lock();
    if (pList)
-      pList->DataEvent( Pointer(this), code );
+      pList->DataEvent( SharedPointer(), code );
 }
 
 void Track::SyncLockAdjust(double oldT1, double newT1)
@@ -374,7 +374,7 @@ void Track::SyncLockAdjust(double oldT1, double newT1)
 
 std::shared_ptr<Track> Track::FindTrack()
 {
-   return Pointer( this );
+   return SharedPointer();
 }
 
 void PlayableTrack::Init( const PlayableTrack &orig )
@@ -1162,7 +1162,8 @@ namespace {
       if ( ! includeMuted )
          subRange = subRange - &Type::GetMute;
       return transform_range<Array>( subRange.begin(), subRange.end(),
-          []( Type *t ){ return Track::Pointer<Type>( t ); } );
+         []( Type *t ){ return t->template SharedPointer<Type>(); }
+      );
    }
 }
 
@@ -1375,7 +1376,7 @@ std::shared_ptr<const Track> Track::SubstitutePendingChangedTrack() const
       if (it != end)
          return *it;
    }
-   return Pointer( this );
+   return SharedPointer();
 }
 
 std::shared_ptr<const Track> Track::SubstituteOriginalTrack() const
@@ -1395,7 +1396,7 @@ std::shared_ptr<const Track> Track::SubstituteOriginalTrack() const
             return *it2;
       }
    }
-   return Pointer( this );
+   return SharedPointer();
 }
 
 bool TrackList::HasPendingTracks() const

src/Track.h

@@ -190,6 +190,7 @@ private:
 
 class AUDACITY_DLL_API Track /* not final */
    : public CommonTrackPanelCell, public XMLTagHandler
+   , public std::enable_shared_from_this<Track> // see SharedPointer()
 {
    friend class TrackList;
 
@@ -227,31 +228,29 @@ class AUDACITY_DLL_API Track /* not final */
    void SetId( TrackId id ) { mId = id; }
  public:
 
-   // Given a bare pointer, find a shared_ptr.  But this is not possible for
+   // Given a bare pointer, find a shared_ptr.  Undefined results if the track
-   // a track not owned by any project, so the result can be null.
+   // is not yet managed by a shared_ptr.  Undefined results if the track is
+   // not really of the subclass.  (That is, trusts the caller and uses static
+   // not dynamic casting.)
    template<typename Subclass = Track>
-   inline static std::shared_ptr<Subclass> Pointer( Track *t )
+   inline std::shared_ptr<Subclass> SharedPointer()
    {
-      if (t) {
+      // shared_from_this is injected into class scope by base class
-         auto pList = t->mList.lock();
+      // std::enable_shared_from_this<Track>
-         if (pList)
+      if (!this) return {};
-            return std::static_pointer_cast<Subclass>(*t->mNode.first);
+      return std::static_pointer_cast<Subclass>( shared_from_this() );
-      }
-      return {};
    }
 
    template<typename Subclass = const Track>
-   inline static std::shared_ptr<Subclass> Pointer( const Track *t )
+   inline auto SharedPointer() const -> typename
+      std::enable_if<
+         std::is_const<Subclass>::value, std::shared_ptr<Subclass>
+      >::type
    {
-      if (t) {
+      // shared_from_this is injected into class scope by base class
-         auto pList = t->mList.lock();
+      // std::enable_shared_from_this<Track>
-         if (pList) {
+      if (!this) return {};
-            std::shared_ptr<const Track> p{ *t->mNode.first };
+      return std::static_pointer_cast<Subclass>( shared_from_this() );
-            // Let you change the type, but not cast away the const
-            return std::static_pointer_cast<Subclass>(p);
-         }
-      }
-      return {};
    }
 
    // Find anything registered with TrackList::RegisterPendingChangedTrack and

src/TrackArtist.cpp

@@ -2022,7 +2022,7 @@ void TrackArt::DrawSpectrum( TrackPanelDrawingContext &context,
    DrawBackgroundWithSelection(
       context, rect, track, blankSelectedBrush, blankBrush );
 
-   WaveTrackCache cache(Track::Pointer<const WaveTrack>(track));
+   WaveTrackCache cache(track->SharedPointer<const WaveTrack>());
    for (const auto &clip: track->GetClips())
       DrawClipSpectrum( context, cache, clip.get(), rect );
 }

src/TrackPanel.cpp

@@ -2054,10 +2054,10 @@ struct ChannelGroup final : TrackPanelGroup {
       for ( auto channel : channels ) {
          refinement.emplace_back( yy,
             std::make_shared< VRulerAndChannel >(
-               Track::Pointer( channel ), mLeftOffset ) );
+               channel->SharedPointer(), mLeftOffset ) );
          if ( channel != pLast ) {
             const auto substitute =
-               Track::Pointer( channel )->SubstitutePendingChangedTrack();
+               channel->SubstitutePendingChangedTrack();
             yy += substitute->GetHeight();
             refinement.emplace_back(
                yy - kSeparatorThickness, channel->GetResizer() );
@@ -2120,12 +2120,12 @@ struct Subgroup final : TrackPanelGroup {
          wxCoord height = 0;
          for ( auto channel : TrackList::Channels( leader ) ) {
             auto substitute =
-               Track::Pointer( channel )->SubstitutePendingChangedTrack();
+               channel->SubstitutePendingChangedTrack();
             height += substitute->GetHeight();
          }
          refinement.emplace_back( yy,
             std::make_shared< ResizingChannelGroup >(
-               Track::Pointer( leader ), mPanel.GetLeftOffset() )
+               leader->SharedPointer(), mPanel.GetLeftOffset() )
          );
          yy += height;
       }
@@ -2241,7 +2241,7 @@ void TrackPanel::SetFocusedTrack( Track *t )
    // Make sure we always have the first linked track of a stereo track
    t = *GetTracks()->FindLeader(t);
 
-   auto cell = mAx->SetFocus( Track::Pointer( t ) ).get();
+   auto cell = mAx->SetFocus( t->SharedPointer() ).get();
 
    if (cell) {
       AudacityProject::CaptureKeyboard(this);

src/TrackPanelAx.cpp

@@ -62,7 +62,8 @@ std::shared_ptr<Track> TrackPanelAx::GetFocus()
          focusedTrack = FindTrack(mNumFocusedTrack);
       }
       if (!focusedTrack) {
-         focusedTrack = Track::Pointer( *mTrackPanel->GetTracks()->Any().first );
+         focusedTrack =
+            (*mTrackPanel->GetTracks()->Any().first)->SharedPointer();
          // only call SetFocus if the focus has changed to avoid
          // unnecessary focus events
          if (focusedTrack) 
@@ -97,7 +98,7 @@ std::shared_ptr<Track> TrackPanelAx::SetFocus( std::shared_ptr<Track> track )
 #endif
 
    if( !track )
-      track = Track::Pointer( *mTrackPanel->GetTracks()->Any().begin() );
+      track = (*mTrackPanel->GetTracks()->Any().begin())->SharedPointer();
 
    mFocusedTrack = track;
    mNumFocusedTrack = TrackNum(track);
@@ -175,7 +176,7 @@ std::shared_ptr<Track> TrackPanelAx::FindTrack( int num )
    {
       ndx++;
       if( ndx == num )
-         return Track::Pointer( t );
+         return t->SharedPointer();
    }
 
    return {};

src/toolbars/ControlToolBar.cpp

@@ -939,7 +939,7 @@ WaveTrackArray ControlToolBar::ChooseExistingRecordingTracks(
          }
          channelCounts.push_back(nChannels);
          for ( auto channel : channels ) {
-            candidates.push_back(Track::Pointer<WaveTrack>(channel));
+            candidates.push_back(channel->SharedPointer<WaveTrack>());
             if(candidates.size() == recordingChannels)
                // Done!
                return candidates;

src/tracks/labeltrack/ui/LabelDefaultClickHandle.cpp

@@ -37,7 +37,7 @@ void LabelDefaultClickHandle::SaveState( AudacityProject *pProject )
 
    for (auto lt : tracks->Any<LabelTrack>())
       pairs.push_back( std::make_pair(
-         Track::Pointer<LabelTrack>( lt ), lt->SaveFlags() ) );
+         lt->SharedPointer<LabelTrack>(), lt->SaveFlags() ) );
 }
 
 void LabelDefaultClickHandle::RestoreState( AudacityProject *pProject )

src/tracks/labeltrack/ui/LabelTrackUI.cpp

@@ -30,12 +30,12 @@ std::vector<UIHandlePtr> LabelTrack::DetailedHitTest
    const wxMouseState &state = st.state;
 
    result = LabelGlyphHandle::HitTest(
-      mGlyphHandle, state, Pointer<LabelTrack>(this), st.rect);
+      mGlyphHandle, state, SharedPointer<LabelTrack>(), st.rect);
    if (result)
       results.push_back(result);
 
    result = LabelTextHandle::HitTest(
-      mTextHandle, state, Pointer<LabelTrack>(this));
+      mTextHandle, state, SharedPointer<LabelTrack>());
    if (result)
       results.push_back(result);
 
@@ -44,10 +44,10 @@ std::vector<UIHandlePtr> LabelTrack::DetailedHitTest
 
 std::shared_ptr<TrackControls> LabelTrack::GetControls()
 {
-   return std::make_shared<LabelTrackControls>( Pointer( this ) );
+   return std::make_shared<LabelTrackControls>( SharedPointer() );
 }
 
 std::shared_ptr<TrackVRulerControls> LabelTrack::GetVRulerControls()
 {
-   return std::make_shared<LabelTrackVRulerControls>( Pointer( this ) );
+   return std::make_shared<LabelTrackVRulerControls>( SharedPointer() );
 }

src/tracks/playabletrack/notetrack/ui/NoteTrackUI.cpp

@@ -43,11 +43,11 @@ std::vector<UIHandlePtr> NoteTrack::DetailedHitTest
 
 std::shared_ptr<TrackControls> NoteTrack::GetControls()
 {
-   return std::make_shared<NoteTrackControls>( Pointer( this ) );
+   return std::make_shared<NoteTrackControls>( SharedPointer() );
 }
 
 std::shared_ptr<TrackVRulerControls> NoteTrack::GetVRulerControls()
 {
-   return std::make_shared<NoteTrackVRulerControls>( Pointer( this ) );
+   return std::make_shared<NoteTrackVRulerControls>( SharedPointer() );
 }
 #endif

src/tracks/playabletrack/wavetrack/ui/WaveTrackUI.cpp

@@ -41,7 +41,7 @@ std::vector<UIHandlePtr> WaveTrack::DetailedHitTest
       // (But this does not do the time shift constrained to the vertical only,
       //  which is what happens when you hold Ctrl in the Time Shift tool mode)
       result = TimeShiftHandle::HitAnywhere(
-         mTimeShiftHandle, Pointer(this), false);
+         mTimeShiftHandle, SharedPointer(), false);
       if (result)
          results.push_back(result);
       return results;
@@ -53,7 +53,7 @@ std::vector<UIHandlePtr> WaveTrack::DetailedHitTest
 
       if (NULL != (result = CutlineHandle::HitTest(
          mCutlineHandle, st.state, st.rect,
-         pProject, Pointer<WaveTrack>(this))))
+         pProject, SharedPointer<WaveTrack>())))
          // This overriding test applies in all tools
          results.push_back(result);
       if (bMultiTool) {
@@ -63,16 +63,16 @@ std::vector<UIHandlePtr> WaveTrack::DetailedHitTest
          // point, seems arbitrary
          if (NULL != (result = EnvelopeHandle::WaveTrackHitTest(
             mEnvelopeHandle, st.state, st.rect,
-            pProject, Pointer<WaveTrack>(this))))
+            pProject, SharedPointer<WaveTrack>())))
             results.push_back(result);
          if (NULL != (result = TimeShiftHandle::HitTest(
-            mTimeShiftHandle, st.state, st.rect, Pointer(this))))
+            mTimeShiftHandle, st.state, st.rect, SharedPointer())))
             // This is the hit test on the "grips" drawn left and
             // right in Multi only
             results.push_back(result);
          if (NULL != (result = SampleHandle::HitTest(
             mSampleHandle, st.state, st.rect,
-            pProject, Pointer<WaveTrack>(this))))
+            pProject, SharedPointer<WaveTrack>())))
             results.push_back(result);
       }
       else {
@@ -87,7 +87,7 @@ std::vector<UIHandlePtr> WaveTrack::DetailedHitTest
             }
             case drawTool:
                result = SampleHandle::HitAnywhere(
-                  mSampleHandle, st.state, Pointer<WaveTrack>(this));
+                  mSampleHandle, st.state, SharedPointer<WaveTrack>());
                break;
             default:
                result = {};
@@ -103,10 +103,10 @@ std::vector<UIHandlePtr> WaveTrack::DetailedHitTest
 
 std::shared_ptr<TrackControls> WaveTrack::GetControls()
 {
-   return std::make_shared<WaveTrackControls>( Pointer( this ) );
+   return std::make_shared<WaveTrackControls>( SharedPointer() );
 }
 
 std::shared_ptr<TrackVRulerControls> WaveTrack::GetVRulerControls()
 {
-   return std::make_shared<WaveTrackVRulerControls>( Pointer( this ) );
+   return std::make_shared<WaveTrackVRulerControls>( SharedPointer() );
 }

src/tracks/playabletrack/wavetrack/ui/WaveTrackVRulerControls.cpp

@@ -33,7 +33,7 @@ std::vector<UIHandlePtr> WaveTrackVRulerControls::HitTest
    std::vector<UIHandlePtr> results;
 
    if ( st.state.GetX() <= st.rect.GetRight() - kGuard ) {
-      auto pTrack = Track::Pointer<WaveTrack>( FindTrack().get() );
+      auto pTrack = FindTrack()->SharedPointer<WaveTrack>(  );
       if (pTrack) {
          auto result = std::make_shared<WaveTrackVZoomHandle>(
             pTrack, st.rect, st.state.m_y );

src/tracks/timetrack/ui/TimeTrackUI.cpp

@@ -23,8 +23,8 @@ std::vector<UIHandlePtr> TimeTrack::DetailedHitTest
  const AudacityProject *pProject, int, bool)
 {
    std::vector<UIHandlePtr> results;
-   auto result = EnvelopeHandle::TimeTrackHitTest
+   auto result = EnvelopeHandle::TimeTrackHitTest(
-      ( mEnvelopeHandle, st.state, st.rect, pProject, Pointer<TimeTrack>(this) );
+      mEnvelopeHandle, st.state, st.rect, pProject, SharedPointer<TimeTrack>() );
    if (result)
       results.push_back(result);
    return results;
@@ -32,10 +32,10 @@ std::vector<UIHandlePtr> TimeTrack::DetailedHitTest
 
 std::shared_ptr<TrackControls> TimeTrack::GetControls()
 {
-   return std::make_shared<TimeTrackControls>( Pointer( this ) );
+   return std::make_shared<TimeTrackControls>( SharedPointer() );
 }
 
 std::shared_ptr<TrackVRulerControls> TimeTrack::GetVRulerControls()
 {
-   return std::make_shared<TimeTrackVRulerControls>( Pointer( this ) );
+   return std::make_shared<TimeTrackVRulerControls>( SharedPointer() );
 }

src/tracks/ui/SelectHandle.cpp

@@ -639,7 +639,7 @@ UIHandle::Result SelectHandle::Click
          case SBBottom:
          case SBTop:
          {
-            mFreqSelTrack = Track::Pointer<const WaveTrack>( pTrack );
+            mFreqSelTrack = pTrack->SharedPointer<const WaveTrack>();
             mFreqSelPin = value;
             mFreqSelMode =
                (boundary == SBBottom)
@@ -694,7 +694,7 @@ UIHandle::Result SelectHandle::Click
             // Ignore whether we are inside the time selection.
             // Exit center-snapping, start dragging the width.
             mFreqSelMode = FREQ_SEL_PINNED_CENTER;
-            mFreqSelTrack = Track::Pointer<const WaveTrack>( pTrack );
+            mFreqSelTrack = pTrack->SharedPointer<const WaveTrack>();
             mFreqSelPin = viewInfo.selectedRegion.fc();
             // Do not adjust time boundaries
             mSelStartValid = false;
@@ -736,7 +736,7 @@ UIHandle::Result SelectHandle::Click
                startNewSelection = false;
                // Disable time selection
                mSelStartValid = false;
-               mFreqSelTrack = Track::Pointer<const WaveTrack>( pTrack );
+               mFreqSelTrack = pTrack->SharedPointer<const WaveTrack>();
                mFreqSelPin = value;
                mFreqSelMode =
                   (boundary == SBWidth) ? FREQ_SEL_PINNED_CENTER :
@@ -1143,7 +1143,7 @@ void SelectHandle::AdjustSelection
       std::max(0.0, viewInfo.PositionToTime(mouseXCoordinate, trackLeftEdge));
    double origSelend = selend;
 
-   auto pTrack = Track::Pointer( track );
+   auto pTrack = track->SharedPointer();
    if (!pTrack)
       pTrack = pProject->GetTracks()->Lock(mpTrack);
 
@@ -1205,7 +1205,7 @@ void SelectHandle::StartFreqSelection(ViewInfo &viewInfo,
 
    if (isSpectralSelectionTrack(pTrack)) {
       // Spectral selection track is always wave
-      auto shTrack = Track::Pointer<const WaveTrack>( pTrack );
+      auto shTrack = pTrack->SharedPointer<const WaveTrack>();
       mFreqSelTrack = shTrack;
       mFreqSelMode = FREQ_SEL_FREE;
       mFreqSelPin =
@@ -1304,7 +1304,7 @@ void SelectHandle::HandleCenterFrequencyClick
    if (shiftDown) {
       // Disable time selection
       mSelStartValid = false;
-      mFreqSelTrack = Track::Pointer<const WaveTrack>( pTrack );
+      mFreqSelTrack = pTrack->SharedPointer<const WaveTrack>();
       mFreqSelPin = value;
       mFreqSelMode = FREQ_SEL_DRAG_CENTER;
    }
@@ -1405,7 +1405,7 @@ void SelectHandle::MoveSnappingFreqSelection
       // A change here would affect what AdjustFreqSelection() does
       // in the prototype version where you switch from moving center to
       // dragging width with a click.  No effect now.
-      mFreqSelTrack = Track::Pointer<const WaveTrack>( wt );
+      mFreqSelTrack = wt->SharedPointer<const WaveTrack>();
 
       // SelectNone();
       // SelectTrack(pTrack, true);

src/tracks/ui/TimeShiftHandle.cpp

@@ -693,7 +693,7 @@ UIHandle::Result TimeShiftHandle::Drag
    }
 
    // May need a shared_ptr to reassign mCapturedTrack below
-   auto pTrack = Track::Pointer( track );
+   auto pTrack = track->SharedPointer();
    if (!pTrack)
       return RefreshCode::RefreshNone;
 

src/tracks/ui/TrackUI.cpp

@@ -53,7 +53,7 @@ std::vector<UIHandlePtr> Track::HitTest
    // Sliding applies in more than one track type.
    if ( !isMultiTool && currentTool == slideTool ) {
       result = TimeShiftHandle::HitAnywhere(
-         mTimeShiftHandle, Pointer(this), false);
+         mTimeShiftHandle, SharedPointer(), false);
       if (result)
          results.push_back(result);
    }
@@ -70,7 +70,7 @@ std::vector<UIHandlePtr> Track::HitTest
    // Finally, default of all is adjustment of the selection box.
    if ( isMultiTool || currentTool == selectTool ) {
       result = SelectHandle::HitTest(
-         mSelectHandle, st, pProject, Pointer(this));
+         mSelectHandle, st, pProject, SharedPointer());
       if (result)
          results.push_back(result);
    }
@@ -99,6 +99,6 @@ std::shared_ptr<TrackPanelCell> Track::GetResizer()
 {
    if (!mpResizer)
       // create on demand
-      mpResizer = std::make_shared<TrackPanelResizerCell>( Pointer( this ) );
+      mpResizer = std::make_shared<TrackPanelResizerCell>( SharedPointer() );
    return mpResizer;
 }