Method OnUpdate

src/tracks/ui/ChannelView.cpp:266–295

   TrackPositioner &operator=( const TrackPositioner & ) = delete;

   void OnUpdate(const TrackListEvent & e)
   {
      switch (e.mType) {
      case TrackListEvent::ADDITION:
      case TrackListEvent::DELETION:
      case TrackListEvent::PERMUTED:
      case TrackListEvent::RESIZING:
         break;
      default:
         return;
      }
      auto iter =
         TrackList::Get(mProject).Find(e.mpTrack.lock().get());
      if (!*iter)
         iter = TrackList::Get(mProject).begin();
      if (!*iter)
         return;

      auto prev = iter;
      auto yy = ChannelView::GetCumulativeHeight(*--prev);

      while (auto pTrack = *iter) {
         for (auto pChannel : (*iter)->Channels()) {
            auto &view = ChannelView::Get(*pChannel);
            view.SetCumulativeHeightBefore(yy);
            yy += view.GetHeight();
         }
         ++iter;
      }
   }

   Observer::Subscription mSubscription;
};