Define and use SelectionStateChanger

src/SelectionState.cpp

@@ -188,3 +188,39 @@ void SelectionState::TrackListUpdated( const TrackList &tracks )
    if (mLastPickedTrack && !tracks.Contains(mLastPickedTrack))
       mLastPickedTrack = nullptr;
 }
+
+SelectionStateChanger::SelectionStateChanger
+( SelectionState &state, TrackList &tracks )
+   : mpState{ &state }
+   , mTracks{ tracks }
+   , mInitialLastPickedTrack{ state.mLastPickedTrack }
+{
+   // Save initial state of track selections
+   mInitialTrackSelection.clear();
+   TrackListIterator iter( &mTracks );
+   for (Track *track = iter.First(); track; track = iter.Next()) {
+      const bool isSelected = track->GetSelected();
+      mInitialTrackSelection.push_back(isSelected);
+   }
+}
+
+SelectionStateChanger::~SelectionStateChanger()
+{
+   if ( mpState ) {
+      // roll back changes
+      mpState->mLastPickedTrack = mInitialLastPickedTrack;
+      TrackListIterator iter( &mTracks );
+      std::vector<bool>::const_iterator
+         it = mInitialTrackSelection.begin(),
+         end = mInitialTrackSelection.end();
+      for (Track *track = iter.First(); track && it != end; track = iter.Next()) {
+         // wxASSERT(it != end);
+         track->SetSelected( *it++ );
+      }
+   }
+}
+
+void SelectionStateChanger::Commit()
+{
+   mpState = nullptr;
+}

src/SelectionState.h

@@ -13,6 +13,7 @@ class Track;
 class TrackList;
 class MixerBoard;
 class ViewInfo;
+#include <vector>
 
 // State relating to the set of selected tracks
 class SelectionState
@@ -37,7 +38,29 @@ public:
 
    void TrackListUpdated( const TrackList &tracks );
 
+private:
+   friend class SelectionStateChanger;
+
    Track *mLastPickedTrack {};
 };
 
+// For committing or rolling-back of changes in selectedness of tracks.
+// When rolling back, it is assumed that no tracks have been added or removed.
+class SelectionStateChanger
+{
+public:
+   SelectionStateChanger( SelectionState &state, TrackList &tracks );
+   SelectionStateChanger( const SelectionStateChanger& ) = delete;
+   SelectionStateChanger &operator=( const SelectionStateChanger& ) = delete;
+
+   ~SelectionStateChanger();
+   void Commit();
+
+private:
+   SelectionState *mpState;
+   TrackList &mTracks;
+   Track *mInitialLastPickedTrack;
+   std::vector<bool> mInitialTrackSelection;
+};
+
 #endif

src/TrackPanel.cpp

@@ -1151,15 +1151,7 @@ bool TrackPanel::HandleEscapeKey(bool down)
    {
    case IsSelecting:
    {
-      TrackListIterator iter(GetTracks());
-      std::vector<bool>::const_iterator
-         it = mInitialTrackSelection.begin(),
-         end = mInitialTrackSelection.end();
-      for (Track *t = iter.First(); t; t = iter.Next()) {
-         wxASSERT(it != end);
-         t->SetSelected(*it++);
-      }
-      GetSelectionState().mLastPickedTrack = mInitialLastPickedTrack;
+      mSelectionStateChanger.reset();
       mViewInfo->selectedRegion = mInitialSelection;
 
       // Refresh mixer board for change of set of selected tracks
@@ -1789,6 +1781,10 @@ void TrackPanel::HandleSelect(wxMouseEvent & event)
          SelectionHandleClick(event, t, rect);
    } else if (event.LeftUp() || event.RightUp()) {
       mSnapManager.reset();
+      if (mSelectionStateChanger) {
+         mSelectionStateChanger->Commit();
+         mSelectionStateChanger.reset();
+      }
 
       bool left;
       if ( GetProject()->IsSyncLocked() &&
@@ -1931,17 +1927,8 @@ void TrackPanel::SelectionHandleClick(wxMouseEvent & event,
 
    mMouseCapture=IsSelecting;
    mInitialSelection = mViewInfo->selectedRegion;
-   mInitialLastPickedTrack = GetSelectionState().mLastPickedTrack;
-
-   // Save initial state of track selections
-   mInitialTrackSelection.clear();
-   {
-      TrackListIterator iter(GetTracks());
-      for (Track *t = iter.First(); t; t = iter.Next()) {
-         const bool isSelected = t->GetSelected();
-         mInitialTrackSelection.push_back(isSelected);
-      }
-   }
+   mSelectionStateChanger = std::make_unique< SelectionStateChanger >
+      ( GetSelectionState(), *mTracks );
 
    // We create a NEW snap manager in case any snap-points have changed
    mSnapManager = std::make_unique<SnapManager>(GetTracks(), mViewInfo);

src/TrackPanel.h

@@ -639,10 +639,9 @@ protected:
    bool mRefreshBacking;
 
    SelectedRegion mInitialSelection;
-   std::vector<bool> mInitialTrackSelection;
    SelectionState mSelectionState{};
    SelectionState &GetSelectionState() { return mSelectionState; }
-   Track *mInitialLastPickedTrack {};
+   std::unique_ptr<SelectionStateChanger> mSelectionStateChanger{};
 
    bool mSelStartValid;
    double mSelStart;