Function DoNextTrack

src/menus/NavigationMenus.cpp:183–284

The following method moves to the next track, selecting and unselecting depending if you are on the start of a block or not.

/// selecting and unselecting depending if you are on the start of a
/// block or not.
void DoNextTrack(
   AudacityProject &project, bool shift, bool circularTrackNavigation )
{
   auto &projectHistory = ProjectHistory::Get(project);
   auto &trackFocus = TrackFocus::Get(project);
   auto &tracks = TrackList::Get(project);
   auto &selectionState = SelectionState::Get(project);
   auto &viewport = Viewport::Get(project);

   const auto t = trackFocus.Get();
   if  (!t) {
      // if there isn't one, focus on first
      const auto first = *tracks.begin();
      trackFocus.Set(first);
      if (first) {
         viewport.ShowTrack(*first);
         projectHistory.ModifyState(false);
      }
      return;
   }

   if (shift) {
      auto n = * ++ tracks.Find(t); // Get next track
      if (!n) {
         // On last track so stay there
         wxBell();
         if (circularTrackNavigation)
            n = *tracks.begin();
         else {
            viewport.ShowTrack(*t);
            return;
         }
      }
      // If here, then there is a nonempty list and a next track
      // (maybe circularly)
      assert(n);
      auto tSelected = t->GetSelected();
      auto nSelected = n->GetSelected();
      if (tSelected && nSelected) {
         selectionState.SelectTrack(*t, false, false);
         trackFocus.Set(n);   // move focus to next track down
         if (n) {
            viewport.ShowTrack(*n);
            projectHistory.ModifyState(false);
         }
         return;
      }
      if (tSelected && !nSelected) {
         selectionState.SelectTrack(*n, true, false);
         trackFocus.Set(n);   // move focus to next track down
         if (n) {
            viewport.ShowTrack(*n);
            projectHistory.ModifyState(false);
         }
         return;
      }
      if (!tSelected && nSelected) {
         selectionState.SelectTrack(*n, false, false);