New method of TrackShifter moves a calculation out of ClipMenus

src/menus/ClipMenus.cpp

@@ -646,10 +646,8 @@ double DoClipMove
          uShifter = MakeTrackShifter::Call( *wt );
          if( uShifter->HitTest( t0 ) == TrackShifter::HitTestResult::Miss )
             uShifter.reset();
-         else {
-            wt = channel;
+         else
             break;
-         }
       }
 
       if (!uShifter)
@@ -660,16 +658,7 @@ double DoClipMove
          t0, viewInfo, trackList, syncLocked );
 
       auto desiredT0 = viewInfo.OffsetTimeByPixels( t0, ( right ? 1 : -1 ) );
-      auto desiredSlideAmount = desiredT0 - t0;
-
-      // set it to a sample point, and minimum of 1 sample point
-      if (!right)
-         desiredSlideAmount *= -1;
-      double nSamples = rint(wt->GetRate() * desiredSlideAmount);
-      nSamples = std::max(nSamples, 1.0);
-      desiredSlideAmount = nSamples / wt->GetRate();
-      if (!right)
-         desiredSlideAmount *= -1;
+      auto desiredSlideAmount = pShifter->HintOffsetLarger( desiredT0 - t0 );
 
       auto hSlideAmount =
          state.DoSlideHorizontal( desiredSlideAmount, trackList );

src/tracks/playabletrack/wavetrack/ui/WaveTrackView.cpp

@@ -1344,6 +1344,20 @@ public:
 
    bool SyncLocks() override { return true; }
 
+   double HintOffsetLarger(double desiredOffset) override
+   {
+      // set it to a sample point, and minimum of 1 sample point
+      bool positive = (desiredOffset > 0);
+      if (!positive)
+         desiredOffset *= -1;
+      double nSamples = rint(mpTrack->GetRate() * desiredOffset);
+      nSamples = std::max(nSamples, 1.0);
+      desiredOffset = nSamples / mpTrack->GetRate();
+      if (!positive)
+         desiredOffset *= -1;
+      return desiredOffset;
+   }
+
 private:
    std::shared_ptr<WaveTrack> mpTrack;
 };

src/tracks/ui/TimeShiftHandle.cpp

@@ -274,6 +274,11 @@ void TrackShifter::CommonSelectInterval(const TrackInterval &interval)
    });
 }
 
+double TrackShifter::HintOffsetLarger(double desiredOffset)
+{
+   return desiredOffset;
+}
+
 void TrackShifter::InitIntervals()
 {
    mMoving.clear();
@@ -960,6 +965,8 @@ UIHandle::Result TimeShiftHandle::Drag
    if (desiredSlideAmount == 0.0)
       return RefreshAll;
 
+   // Note that mouse dragging doesn't use TrackShifter::HintOffsetLarger()
+
    mClipMoveState.DoSlideHorizontal( desiredSlideAmount, trackList );
 
    if (mClipMoveState.movingSelection) {

src/tracks/ui/TimeShiftHandle.h

@@ -65,6 +65,16 @@ public:
    //! Whether unfixing of an interval should propagate to all overlapping intervals in the sync lock group
    virtual bool SyncLocks() = 0;
 
+   //! Given amount to shift by horizontally, maybe adjust it from zero to suggest minimum distance
+   /*!
+    Any interval placement constraints, not necessarily met at the suggested offset
+    Default implementation returns the argument
+    @post `fabs(r) >= fabs(desiredOffset)`
+    @post `r * desiredOffset >= 0` (i.e. signs are not opposite)
+    @post (where `r` is return value)
+    */
+   virtual double HintOffsetLarger( double desiredOffset );
+
 protected:
    /*! Unfix any of the intervals that intersect the given one; may be useful to override `SelectInterval()` */
    void CommonSelectInterval( const TrackInterval &interval );