Method Calculate

src/HistoryWindow.cpp:74–109

   Type clipboardSpaceUsage;

   void Calculate( UndoManager &manager )
   {
      SampleBlockIDSet seen;

      // After copies and pastes, a block file may be used in more than
      // one place in one undo history state, and it may be used in more than
      // one undo history state.  It might even be used in two states, but not
      // in another state that is between them -- as when you have state A,
      // then make a cut to get state B, but then paste it back into state C.

      // So be sure to count each block file once only, in the last undo item that
      // contains it.

      // Why the last and not the first? Because the user of the History dialog
      // may DELETE undo states, oldest first.  To reclaim disk space you must
      // DELETE all states containing the block file.  So the block file's
      // contribution to space usage should be counted only in that latest
      // state.

      manager.VisitStates(
         [this, &seen](const UndoStackElem &elem) {
            // Scan all tracks at current level
            if (auto pTracks = UndoTracks::Find(elem))
               space.push_back(CalculateUsage(*pTracks, seen));
         },
         true // newest state first
      );

      // Count the usage of the clipboard separately, using another set.  Do not
      // multiple-count any block occurring multiple times within the clipboard.
      seen.clear();
      clipboardSpaceUsage = CalculateUsage(
         Clipboard::Get().GetTracks(), seen);

      //TIMER_STOP( space_calc );
   }
};
}