Pass optional extra information into TrackShifter::HitTest ...

... Because LabelTrack, unlike the others, will also need a mouse y coordinate.

The extra information is present when using the time-shift tool but not when
using the items in ClipMenus.

src/tracks/playabletrack/notetrack/ui/NoteTrackView.cpp

@@ -742,7 +742,7 @@ public:
    ~NoteTrackShifter() override {}
    Track &GetTrack() const override { return *mpTrack; }
    
-   HitTestResult HitTest( double ) override
+   HitTestResult HitTest( double, HitTestParams* ) override
    {
       return HitTestResult::Intervals;
    }

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

@@ -1314,7 +1314,7 @@ public:
    ~WaveTrackShifter() override {}
    Track &GetTrack() const override { return *mpTrack; }
 
-   HitTestResult HitTest( double time ) override
+   HitTestResult HitTest( double time, HitTestParams* ) override
    {
       auto pClip = mpTrack->GetClipAtTime( time );
 

src/tracks/ui/TimeShiftHandle.cpp

@@ -241,7 +241,7 @@ CoarseTrackShifter::CoarseTrackShifter( Track &track )
 
 CoarseTrackShifter::~CoarseTrackShifter() = default;
 
-auto CoarseTrackShifter::HitTest( double ) -> HitTestResult
+auto CoarseTrackShifter::HitTest( double, HitTestParams* ) -> HitTestResult
 {
    return HitTestResult::Track;
 }
@@ -462,7 +462,10 @@ UIHandle::Result TimeShiftHandle::Click
    auto pShifter = MakeTrackShifter::Call( *pTrack );
 
    if (!event.ShiftDown()) {
-      switch( pShifter->HitTest( clickTime ) ) {
+      TrackShifter::HitTestParams params{
+         rect, event.m_x, event.m_y
+      };
+      switch( pShifter->HitTest( clickTime, &params ) ) {
       case TrackShifter::HitTestResult::Miss:
          return Cancelled;
       case TrackShifter::HitTestResult::Intervals: {

src/tracks/ui/TimeShiftHandle.h

@@ -25,6 +25,8 @@ class TrackList;
 class Track;
 class TrackInterval;
 
+class ViewInfo;
+
 //! Abstract base class for policies to manipulate a track type with the Time Shift tool
 class TrackShifter {
 public:
@@ -39,9 +41,21 @@ public:
       Track      //<! Shift selected track only as a whole
    };
 
+   //! Optional, more complete information for hit testing
+   struct HitTestParams {
+      wxRect rect;
+      wxCoord xx, yy;
+   };
+
    //! Decide how shift behaves, based on the track that is clicked in
    /*! If the return value is Intervals, then some intervals may be marked moving as a side effect */
-   virtual HitTestResult HitTest( double time ) = 0;
+   /*!
+    @pre `!pParams || (time == pParams->viewInfo.PositionToTime(pParams->xx, pParams->rect.x))`
+    */
+   virtual HitTestResult HitTest(
+      double time, //!< A time value to test
+      HitTestParams *pParams = nullptr //!< Optional extra information
+   ) = 0;
 
    using Intervals = std::vector<TrackInterval>;
 
@@ -158,7 +172,7 @@ public:
    ~CoarseTrackShifter() override;
    Track &GetTrack() const override { return *mpTrack; }
 
-   HitTestResult HitTest( double ) override;
+   HitTestResult HitTest( double, HitTestParams* ) override;
 
    //! Returns false
    bool SyncLocks() override;