Define and use SelectionStateChanger

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