Method DoSlideVertical

src/tracks/ui/TimeShiftHandle.cpp:725–807

}

void TimeShiftHandle::DoSlideVertical(
   ViewInfo &viewInfo, wxCoord xx,
   TrackList &trackList, Track *dstTrack, double& desiredSlideAmount)
{
   Correspondence correspondence;

   // See if captured track corresponds to another
   auto &capturedTrack = *mClipMoveState.mCapturedTrack;
   if (!FindCorrespondence(
      correspondence, trackList, capturedTrack, *dstTrack, mClipMoveState ))
      return;

   // Try to extend the correpondence
   auto tryExtend = [&](bool forward) {
      auto range = trackList.Any();
      auto begin = range.begin(), end = range.end();
      auto pCaptured = trackList.Find(&capturedTrack);
      auto pDst = trackList.Find(dstTrack);
      // Scan for more correspondences
      while (true) {
         // Remember that TrackIter wraps circularly to the end iterator when
         // decrementing it

         // First move to a track with moving intervals and
         // without a correspondent
         do
            forward ? ++pCaptured : --pCaptured;
         while (pCaptured != end &&
            (correspondence.count(*pCaptured) ||
             mClipMoveState.shifters[*pCaptured]->MovingIntervals().empty()));
         if (pCaptured == end)
            break;

         // Change the choice of possible correspondent track too
         do
            forward ? ++pDst : --pDst;
         while (pDst != end && correspondence.count(*pDst));
         if (pDst == end)
            break;

         // Make correspondence if we can
         if (!FindCorrespondence(
            correspondence, trackList, **pCaptured, **pDst, mClipMoveState))
            break;
      }
   };
   // Try extension, backward first, then forward
   // (anticipating the case of dragging a label that is under a clip)
   tryExtend(false);
   tryExtend(true);

   // Having passed that test, remove clips temporarily from their
   // tracks, so moving clips don't interfere with each other
   // when we call CanInsertClip()
   TemporaryClipRemover remover{ mClipMoveState };

   // Now check that the move is possible
   auto slideAmount = desiredSlideAmount;