Function AdjustToSnap

src/tracks/ui/TimeShiftHandle.cpp:527–581

namespace {
   void AdjustToSnap(
      const ViewInfo &viewInfo, wxCoord xx,
      SnapManager *pSnapManager,
      bool snapPreferRightEdge,
      ClipMoveState &state,
      double& desiredSlideAmount)
   {
      auto track = state.mCapturedTrack.get();
      double clipLeft, clipRight;

      // Adjust desiredSlideAmount using SnapManager
      if (pSnapManager) {
         auto pInterval = state.CapturedInterval();
         if (pInterval) {
            clipLeft = pInterval->Start() + desiredSlideAmount;
            clipRight = pInterval->End() + desiredSlideAmount;
         }
         else {
            clipLeft = track->GetStartTime() + desiredSlideAmount;
            clipRight = track->GetEndTime() + desiredSlideAmount;
         }

         auto results =
            pSnapManager->Snap(track, clipLeft, false);
         auto newClipLeft = results.outTime;
         results =
            pSnapManager->Snap(track, clipRight, false);
         auto newClipRight = results.outTime;

         // Only one of them is allowed to snap
         if (newClipLeft != clipLeft && newClipRight != clipRight) {
            // Un-snap the un-preferred edge
            if (snapPreferRightEdge)
               newClipLeft = clipLeft;
            else
               newClipRight = clipRight;
         }

         // Take whichever one snapped (if any) and compute the NEW desiredSlideAmount
         state.snapLeft = -1;
         state.snapRight = -1;
         if (newClipLeft != clipLeft) {
            const double difference = (newClipLeft - clipLeft);
            desiredSlideAmount += difference;
            state.snapLeft =
               viewInfo.TimeToPosition(newClipLeft, xx);
         }
         else if (newClipRight != clipRight) {
            const double difference = (newClipRight - clipRight);
            desiredSlideAmount += difference;
            state.snapRight =
               viewInfo.TimeToPosition(newClipRight, xx);
         }
      }
   }

   using Correspondence = std::unordered_map< Track*, Track* >;