Rename TrackPanel::HandleCursor as HandleMotion...

Call HitTest in just one place

Can now preserve repeatedly hit UIHandle objects during pre-click motion

Fields of HitTestResult besides the handle pointer are now unused

The need to repaint a track during mouse movement can be indicated when
constructing a UIHandle or when updating it for move; HitPreview no longer
does this

And the last allows simplifications of LabelTrack glyph highlighting

Also move the temporary state for label glyph dragging out of LabelTrack

src/HitTestResult.h

@@ -24,17 +24,12 @@ struct HitTestPreview
    HitTestPreview()
    {}
 
-   HitTestPreview(const wxString &message_, wxCursor *cursor_
+   HitTestPreview(const wxString &message_, wxCursor *cursor_)
-      , unsigned refreshCode_ = 0)
+      : message(message_), cursor(cursor_)
-      : message(message_), cursor(cursor_), refreshCode(refreshCode_)
    {}
 
    wxString message {};
    wxCursor *cursor {};
-
-   // Making this non-zero allows mouse-over highlighting
-   // See RefreshCode.h for bit flags:
-   unsigned refreshCode {};
 };
 
 struct HitTestResult

src/LabelTrack.cpp

@@ -102,14 +102,9 @@ LabelTrack::Holder TrackFactory::NewLabelTrack()
 
 LabelTrack::LabelTrack(const std::shared_ptr<DirManager> &projDirManager):
    Track(projDirManager),
-   mbHitCenter(false),
-   mOldEdge(-1),
    mSelIndex(-1),
-   mMouseOverLabelLeft(-1),
-   mMouseOverLabelRight(-1),
    mRestoreFocus(-1),
    mClipLen(0.0),
-   mIsAdjustingLabel(false),
    miLastLabel(-1)
 {
    SetDefaultName(_("Label Track"));
@@ -129,13 +124,8 @@ LabelTrack::LabelTrack(const std::shared_ptr<DirManager> &projDirManager):
 
 LabelTrack::LabelTrack(const LabelTrack &orig) :
    Track(orig),
-   mbHitCenter(false),
-   mOldEdge(-1),
    mSelIndex(-1),
-   mMouseOverLabelLeft(-1),
+   mClipLen(0.0)
-   mMouseOverLabelRight(-1),
-   mClipLen(0.0),
-   mIsAdjustingLabel(false)
 {
    for (auto &original: orig.mLabels) {
       LabelStruct l { original.selectedRegion, original.title };
@@ -766,6 +756,23 @@ void LabelTrack::CalcHighlightXs(int *x1, int *x2) const
    labelStruct.getXPos(dc, x2, pos2);
 }
 
+#include "tracks/labeltrack/ui/LabelGlyphHandle.h"
+// TODO:  don't rely on the global ::GetActiveProject() to find this.
+// Rather, give TrackPanelCell a drawing function and pass context into it.
+namespace {
+   LabelTrackHit *findHit()
+   {
+      // Fetch the highlighting state
+      auto target = GetActiveProject()->GetTrackPanel()->Target();
+      if (target) {
+         auto handle = dynamic_cast<LabelGlyphHandle*>( target->handle.get() );
+         if (handle)
+            return &handle->mHit;
+      }
+      return nullptr;
+   }
+}
+
 /// Draw calls other functions to draw the LabelTrack.
 ///   @param  dc the device context
 ///   @param  r  the LabelTrack rectangle.
@@ -773,6 +780,8 @@ void LabelTrack::Draw(wxDC & dc, const wxRect & r,
    const SelectedRegion &selectedRegion,
    const ZoomInfo &zoomInfo) const
 {
+   auto pHit = findHit();
+
    if(msFont.Ok())
       dc.SetFont(msFont);
 
@@ -819,10 +828,10 @@ void LabelTrack::Draw(wxDC & dc, const wxRect & r,
    { int i = -1; for (auto &labelStruct : mLabels) { ++i;
       GlyphLeft=0;
       GlyphRight=1;
-      if( i==mMouseOverLabelLeft )
+      if( pHit && i == pHit->mMouseOverLabelLeft )
-         GlyphLeft = mbHitCenter ? 6:9;
+         GlyphLeft = (pHit->mEdge & 4) ? 6:9;
-      if( i==mMouseOverLabelRight )
+      if( pHit && i == pHit->mMouseOverLabelRight )
-         GlyphRight = mbHitCenter ? 7:4;
+         GlyphRight = (pHit->mEdge & 4) ? 7:4;
       labelStruct.DrawGlyphs( dc, r, GlyphLeft, GlyphRight );
    }}
 
@@ -1119,20 +1128,10 @@ void LabelTrack::SetSelected(bool s)
       Unselect();
 }
 
-/// OverGlyph returns 0 if not over a glyph,
-/// 1 if over the left-hand glyph, and
-/// 2 if over the right-hand glyph on a label.
-/// 3 if over both right and left.
-///
-/// It also sets up member variables:
-///   mMouseLabelLeft - index of any left label hit
-///   mMouseLabelRight - index of any right label hit
-///   mbHitCenter     - if (x,y) 'hits the spot'.
-///
 /// TODO: Investigate what happens with large
 /// numbers of labels, might need a binary search
 /// rather than a linear one.
-int LabelTrack::OverGlyph(int x, int y)
+void LabelTrack::OverGlyph(LabelTrackHit &hit, int x, int y) const
 {
    //Determine the NEW selection.
    int result=0;
@@ -1140,9 +1139,9 @@ int LabelTrack::OverGlyph(int x, int y)
    const int d2=5;  //distance in pixels, used for have we hit drag handle center.
 
    //If not over a label, reset it
-   mMouseOverLabelLeft  = -1;
+   hit.mMouseOverLabelLeft  = -1;
-   mMouseOverLabelRight = -1;
+   hit.mMouseOverLabelRight = -1;
-   mbHitCenter = false;
+   hit.mEdge = 0;
    { int i = -1; for (auto &labelStruct : mLabels) { ++i;
       //over left or right selection bound
       //Check right bound first, since it is drawn after left bound,
@@ -1150,16 +1149,16 @@ int LabelTrack::OverGlyph(int x, int y)
       if( abs(labelStruct.y - (y - (LabelTrack::mTextHeight+3)/2)) < d1 &&
                abs(labelStruct.x1 - d2 -x) < d1)
       {
-         mMouseOverLabelRight = i;
+         hit.mMouseOverLabelRight = i;
          if(abs(labelStruct.x1 - x) < d2 )
          {
-            mbHitCenter = true;
+            result |= 4;
             // If left and right co-incident at this resolution, then we drag both.
             // We could be a little less stringent about co-incidence here if we liked.
             if( abs(labelStruct.x1-labelStruct.x) < 1.0 )
             {
                result |=1;
-               mMouseOverLabelLeft = i;
+               hit.mMouseOverLabelLeft = i;
             }
          }
          result |= 2;
@@ -1169,9 +1168,9 @@ int LabelTrack::OverGlyph(int x, int y)
       else if(   abs(labelStruct.y - (y - (LabelTrack::mTextHeight+3)/2)) < d1 &&
             abs(labelStruct.x + d2 - x) < d1 )
       {
-         mMouseOverLabelLeft = i;
+         hit.mMouseOverLabelLeft = i;
          if(abs(labelStruct.x - x) < d2 )
-            mbHitCenter = true;
+            result |= 4;
          result |= 1;
       }
 
@@ -1182,7 +1181,7 @@ int LabelTrack::OverGlyph(int x, int y)
       }
 
    }}
-   return result;
+   hit.mEdge = result;
 }
 
 int LabelTrack::OverATextBox(int xx, int yy) const
@@ -1403,7 +1402,8 @@ auto LabelStruct::RegionRelation(
 /// @iEdge - which edge is requested to move, -1 for left +1 for right.
 /// @bAllowSwapping - if we can switch which edge is being dragged.
 /// fNewTime - the NEW time for this edge of the label.
-void LabelTrack::MayAdjustLabel( int iLabel, int iEdge, bool bAllowSwapping, double fNewTime)
+void LabelTrack::MayAdjustLabel
+( LabelTrackHit &hit, int iLabel, int iEdge, bool bAllowSwapping, double fNewTime)
 {
    if( iLabel < 0 )
       return;
@@ -1424,9 +1424,7 @@ void LabelTrack::MayAdjustLabel( int iLabel, int iEdge, bool bAllowSwapping, dou
    }
 
    // Swap our record of what we are dragging.
-   int Temp = mMouseOverLabelLeft;
+   std::swap( hit.mMouseOverLabelLeft, hit.mMouseOverLabelRight );
-   mMouseOverLabelLeft = mMouseOverLabelRight;
-   mMouseOverLabelRight = Temp;
 }
 
 // If the index is for a real label, adjust its left and right boundary.
@@ -1450,27 +1448,28 @@ static int Constrain( int value, int min, int max )
    return result;
 }
 
-bool LabelTrack::HandleGlyphDragRelease(const wxMouseEvent & evt,
+bool LabelTrack::HandleGlyphDragRelease
-   wxRect & r, const ZoomInfo &zoomInfo,
+(LabelTrackHit &hit, const wxMouseEvent & evt,
-   SelectedRegion *newSel)
+ wxRect & r, const ZoomInfo &zoomInfo,
+ SelectedRegion *newSel)
 {
    if(evt.LeftUp())
    {
       bool lupd = false, rupd = false;
-      if(mMouseOverLabelLeft>=0) {
+      if( hit.mMouseOverLabelLeft >= 0 ) {
-         auto &labelStruct = mLabels[mMouseOverLabelLeft];
+         auto &labelStruct = mLabels[ hit.mMouseOverLabelLeft ];
          lupd = labelStruct.updated;
          labelStruct.updated = false;
       }
-      if(mMouseOverLabelRight>=0) {
+      if( hit.mMouseOverLabelRight >= 0 ) {
-         auto &labelStruct = mLabels[mMouseOverLabelRight];
+         auto &labelStruct = mLabels[ hit.mMouseOverLabelRight ];
          rupd = labelStruct.updated;
          labelStruct.updated = false;
       }
 
-      mIsAdjustingLabel = false;
+      hit.mIsAdjustingLabel = false;
-      mMouseOverLabelLeft  = -1;
+      hit.mMouseOverLabelLeft  = -1;
-      mMouseOverLabelRight = -1;
+      hit.mMouseOverLabelRight = -1;
       return lupd || rupd;
    }
 
@@ -1483,23 +1482,25 @@ bool LabelTrack::HandleGlyphDragRelease(const wxMouseEvent & evt,
       int x = Constrain( evt.m_x + mxMouseDisplacement - r.x, 0, r.width);
 
       // If exactly one edge is selected we allow swapping
-      bool bAllowSwapping = (mMouseOverLabelLeft >=0 ) ^ ( mMouseOverLabelRight >= 0);
+      bool bAllowSwapping =
+         ( hit.mMouseOverLabelLeft >=0 ) !=
+         ( hit.mMouseOverLabelRight >= 0);
       // If we're on the 'dot' and nowe're moving,
       // Though shift-down inverts that.
       // and if both edges the same, then we're always moving the label.
-      bool bLabelMoving = mbIsMoving;
+      bool bLabelMoving = hit.mbIsMoving;
       bLabelMoving ^= evt.ShiftDown();
-      bLabelMoving |= mMouseOverLabelLeft==mMouseOverLabelRight;
+      bLabelMoving |= ( hit.mMouseOverLabelLeft == hit.mMouseOverLabelRight );
       double fNewX = zoomInfo.PositionToTime(x, 0);
       if( bLabelMoving )
       {
-         MayMoveLabel( mMouseOverLabelLeft,  -1, fNewX );
+         MayMoveLabel( hit.mMouseOverLabelLeft,  -1, fNewX );
-         MayMoveLabel( mMouseOverLabelRight, +1, fNewX );
+         MayMoveLabel( hit.mMouseOverLabelRight, +1, fNewX );
       }
       else
       {
-         MayAdjustLabel( mMouseOverLabelLeft,  -1, bAllowSwapping, fNewX );
+         MayAdjustLabel( hit, hit.mMouseOverLabelLeft,  -1, bAllowSwapping, fNewX );
-         MayAdjustLabel( mMouseOverLabelRight, +1, bAllowSwapping, fNewX );
+         MayAdjustLabel( hit, hit.mMouseOverLabelRight, +1, bAllowSwapping, fNewX );
       }
 
       if( mSelIndex >=0 )
@@ -1508,7 +1509,7 @@ bool LabelTrack::HandleGlyphDragRelease(const wxMouseEvent & evt,
          //the NEW size of the label.
          *newSel = mLabels[mSelIndex].selectedRegion;
       }
-      SortLabels();
+      SortLabels( &hit );
    }
 
    return false;
@@ -1556,23 +1557,24 @@ void LabelTrack::HandleTextDragRelease(const wxMouseEvent & evt)
    return;
 }
 
-void LabelTrack::HandleGlyphClick(const wxMouseEvent & evt,
+void LabelTrack::HandleGlyphClick
-   const wxRect & r, const ZoomInfo &zoomInfo,
+(LabelTrackHit &hit, const wxMouseEvent & evt,
-   SelectedRegion *newSel)
+ const wxRect & r, const ZoomInfo &zoomInfo,
+ SelectedRegion *newSel)
 {
    if (evt.ButtonDown())
    {
       //OverGlyph sets mMouseOverLabel to be the chosen label.
-      int iGlyph = OverGlyph(evt.m_x, evt.m_y);
+      OverGlyph(hit, evt.m_x, evt.m_y);
-      mIsAdjustingLabel = evt.Button(wxMOUSE_BTN_LEFT) &&
+      hit.mIsAdjustingLabel = evt.Button(wxMOUSE_BTN_LEFT) &&
-         iGlyph != 0;
+         ( hit.mEdge & 3 ) != 0;
 
-      if (mIsAdjustingLabel)
+      if (hit.mIsAdjustingLabel)
       {
          float t = 0.0;
          // We move if we hit the centre, we adjust one edge if we hit a chevron.
          // This is if we are moving just one edge.
-         mbIsMoving = mbHitCenter;
+         hit.mbIsMoving = hit.mEdge & 4;
          // When we start dragging the label(s) we don't want them to jump.
          // so we calculate the displacement of the mouse from the drag center
          // and use that in subsequent dragging calculations.  The mouse stays
@@ -1585,27 +1587,27 @@ void LabelTrack::HandleGlyphClick(const wxMouseEvent & evt,
          // position when we start dragging.
 
          // Dragging of three label edges at the same time is not supported (yet).
-         if( (mMouseOverLabelRight >=0) &&
+         if( ( hit.mMouseOverLabelRight >= 0 ) &&
-             (mMouseOverLabelLeft >=0)
+             ( hit.mMouseOverLabelLeft >= 0 )
            )
          {
-            t = (mLabels[mMouseOverLabelRight].getT1() +
+            t = (mLabels[ hit.mMouseOverLabelRight ].getT1() +
-                 mLabels[mMouseOverLabelLeft].getT0()) / 2.0f;
+                 mLabels[ hit.mMouseOverLabelLeft ].getT0()) / 2.0f;
             // If we're moving two edges, then it's a move (label size preserved)
             // if both edges are the same label, and it's an adjust (label sizes change)
             // if we're on a boundary between two different labels.
-            mbIsMoving = (mMouseOverLabelLeft == mMouseOverLabelRight);
+            hit.mbIsMoving =
+               ( hit.mMouseOverLabelLeft == hit.mMouseOverLabelRight );
          }
-         else if(mMouseOverLabelRight >=0)
+         else if( hit.mMouseOverLabelRight >=0)
          {
-            t = mLabels[mMouseOverLabelRight].getT1();
+            t = mLabels[ hit.mMouseOverLabelRight ].getT1();
          }
-         else if(mMouseOverLabelLeft >=0)
+         else if( hit.mMouseOverLabelLeft >=0)
          {
-            t = mLabels[mMouseOverLabelLeft].getT0();
+            t = mLabels[ hit.mMouseOverLabelLeft ].getT0();
          }
          mxMouseDisplacement = zoomInfo.TimeToPosition(t, r.x) - evt.m_x;
-         return;
       }
    }
 }
@@ -2879,7 +2881,7 @@ bool LabelTrack::IsGoodLabelEditKey(const wxKeyEvent & evt)
 /// This function is called often (whilst dragging a label)
 /// We expect them to be very nearly in order, so insertion
 /// sort (with a linear search) is a reasonable choice.
-void LabelTrack::SortLabels()
+void LabelTrack::SortLabels( LabelTrackHit *pHit )
 {
    const auto begin = mLabels.begin();
    const auto nn = (int)mLabels.size();
@@ -2914,8 +2916,10 @@ void LabelTrack::SortLabels()
                ++index;
          }
       };
-      update(mMouseOverLabelLeft);
+      if ( pHit ) {
-      update(mMouseOverLabelRight);
+         update( pHit->mMouseOverLabelLeft );
+         update( pHit->mMouseOverLabelRight );
+      }
       update(mSelIndex);
    }
 }

src/LabelTrack.h

@@ -39,6 +39,8 @@ class TimeWarper;
 class ZoomInfo;
 
 
+struct LabelTrackHit;
+
 class LabelStruct
 {
 public:
@@ -150,7 +152,6 @@ class AUDACITY_DLL_API LabelTrack final : public Track
              const ZoomInfo &zoomInfo) const;
 
    int getSelectedIndex() const { return mSelIndex; }
-   bool IsAdjustingLabel() const { return mIsAdjustingLabel; }
 
    int GetKind() const override { return Label; }
 
@@ -180,7 +181,7 @@ class AUDACITY_DLL_API LabelTrack final : public Track
 
    void Silence(double t0, double t1) override;
    void InsertSilence(double t, double len) override;
-   int OverGlyph(int x, int y);
+   void OverGlyph(LabelTrackHit &hit, int x, int y) const;
    static wxBitmap & GetGlyph( int i);
 
 
@@ -206,13 +207,16 @@ class AUDACITY_DLL_API LabelTrack final : public Track
    static bool IsTextClipSupported();
 
    void HandleGlyphClick
-      (const wxMouseEvent & evt, const wxRect & r, const ZoomInfo &zoomInfo,
+      (LabelTrackHit &hit,
+       const wxMouseEvent & evt, const wxRect & r, const ZoomInfo &zoomInfo,
        SelectedRegion *newSel);
    void HandleTextClick
       (const wxMouseEvent & evt, const wxRect & r, const ZoomInfo &zoomInfo,
        SelectedRegion *newSel);
-   bool HandleGlyphDragRelease(const wxMouseEvent & evt, wxRect & r, const ZoomInfo &zoomInfo,
+   bool HandleGlyphDragRelease
-      SelectedRegion *newSel);
+      (LabelTrackHit &hit,
+       const wxMouseEvent & evt, wxRect & r, const ZoomInfo &zoomInfo,
+       SelectedRegion *newSel);
    void HandleTextDragRelease(const wxMouseEvent & evt);
 
    bool OnKeyDown(SelectedRegion &sel, wxKeyEvent & event);
@@ -243,7 +247,9 @@ class AUDACITY_DLL_API LabelTrack final : public Track
 
    void CalcHighlightXs(int *x1, int *x2) const;
 
-   void MayAdjustLabel( int iLabel, int iEdge, bool bAllowSwapping, double fNewTime);
+   void MayAdjustLabel
+      ( LabelTrackHit &hit,
+        int iLabel, int iEdge, bool bAllowSwapping, double fNewTime);
    void MayMoveLabel( int iLabel, int iEdge, double fNewTime);
 
    // This pastes labels without shifting existing ones
@@ -266,19 +272,12 @@ class AUDACITY_DLL_API LabelTrack final : public Track
    int FindPrevLabel(const SelectedRegion& currentSelection);
 
  public:
-   void SortLabels();
+   void SortLabels(LabelTrackHit *pHit = nullptr);
-   //These two are used by a TrackPanel KLUDGE, which is why they are public.
-   bool mbHitCenter;
-   //The edge variable tells us what state the icon is in.
-   //mOldEdge is useful for telling us when there has been a state change.
-   int mOldEdge;
  private:
    void ShowContextMenu();
    void OnContextMenu(wxCommandEvent & evt);
 
    int mSelIndex;              /// Keeps track of the currently selected label
-   int mMouseOverLabelLeft;    /// Keeps track of which left label the mouse is currently over.
-   int mMouseOverLabelRight;   /// Keeps track of which right label the mouse is currently over.
    int mxMouseDisplacement;    /// Displacement of mouse cursor from the centre being dragged.
    LabelArray mLabels;
 
@@ -314,9 +313,6 @@ private:
    void calculateFontHeight(wxDC & dc) const;
    void RemoveSelectedText();
 
-   bool mIsAdjustingLabel;
-   bool mbIsMoving;
-
    static wxFont msFont;
 
    std::weak_ptr<LabelGlyphHandle> mGlyphHandle;

src/TrackPanel.cpp

@@ -758,7 +758,7 @@ void TrackPanel::Uncapture(wxMouseEvent *pEvent)
 {
    if (HasCapture())
       ReleaseMouse();
-   HandleCursor( pEvent );
+   HandleMotion( pEvent );
 }
 
 void TrackPanel::CancelDragging()
@@ -768,9 +768,10 @@ void TrackPanel::CancelDragging()
       auto pTrack = GetTracks()->Lock(mpClickedTrack);
       if (pTrack)
          ProcessUIHandleResult(
-            this, mRuler, pTrack.get(), NULL, refreshResult);
+            this, mRuler, pTrack.get(), NULL,
+            refreshResult | mMouseOverUpdateFlags );
       mpClickedTrack.reset();
-      mUIHandle.reset();
+      mUIHandle.reset(), ClearTargets();
       Uncapture();
    }
 }
@@ -830,7 +831,7 @@ void TrackPanel::HandleCursorForLastMouseState()
    // Come here on modifier key or mouse button transitions,
    // or on starting or stopping of play or record,
    // and change the cursor appropriately.
-   HandleCursor( &mLastMouseState );
+   HandleMotion( &mLastMouseState );
 }
 
 bool TrackPanel::IsAudioActive()
@@ -840,10 +841,14 @@ bool TrackPanel::IsAudioActive()
 }
 
 
-///  TrackPanel::HandleCursor( ) sets the cursor drawn at the mouse location.
+///  TrackPanel::HandleMotion( ) sets the cursor drawn at the mouse location,
+///  and updates the status bar message.
+///  We treat certain other changes of mouse button and key state as "motions"
+///  too, and also starting and stopping of playback or recording, all of which
+///  may cause the appropriate cursor and message to change.
 ///  As this procedure checks which region the mouse is over, it is
 ///  appropriate to establish the message in the status bar.
-void TrackPanel::HandleCursor( wxMouseState *pState )
+void TrackPanel::HandleMotion( wxMouseState *pState )
 {
    wxMouseState dummy;
    if (!pState)
@@ -857,39 +862,78 @@ void TrackPanel::HandleCursor( wxMouseState *pState )
    auto &rect = foundCell.rect;
    auto &pCell = foundCell.pCell;
    const TrackPanelMouseState tpmState{ state, rect, pCell };
-   HandleCursor( tpmState );
+   HandleMotion( tpmState );
 }
 
-void TrackPanel::HandleCursor( const TrackPanelMouseState &tpmState )
+void TrackPanel::HandleMotion( const TrackPanelMouseState &tpmState )
 {
-   if ( mUIHandle ) {
+   HitTestResult result;
-      // UIHANDLE PREVIEW
+   auto handle = mUIHandle;
-      // Update status message and cursor during drag
-      HitTestPreview preview = mUIHandle->Preview( tpmState, GetProject() );
-      mListener->TP_DisplayStatusMessage( preview.message );
-      if ( preview.cursor )
-         SetCursor( *preview.cursor );
-   }
-   else {
-      wxCursor *pCursor = NULL;
 
-      wxString tip;
+   auto oldHandle = mLastHitTest.handle;
+   auto oldCell = mLastCell.lock();
+   auto newCell = tpmState.pCell;
 
-      auto pCell = tpmState.pCell;
+   std::shared_ptr<Track> newTrack;
-      auto track = static_cast<CommonTrackPanelCell*>( pCell.get() )->FindTrack();
+   if ( newCell )
-      if (pCell && pCursor == NULL && tip == wxString()) {
+      newTrack = static_cast<CommonTrackPanelCell*>( newCell.get() )->FindTrack();
-         HitTestResult hitTest( pCell->HitTest(tpmState, GetProject()) );
+
-         tip = hitTest.preview.message;
+   std::shared_ptr<Track> oldTrack;
-         ProcessUIHandleResult
+   if ( oldCell )
-            (this, mRuler, track.get(), track.get(), hitTest.preview.refreshCode);
+      oldTrack = static_cast<CommonTrackPanelCell*>( oldCell.get() )->FindTrack();
-         pCursor = hitTest.preview.cursor;
+
-         if (pCursor)
+   wxString tip{};
-            SetCursor(*pCursor);
+   wxCursor *pCursor{};
+   unsigned refreshCode = 0;
+
+   if ( !mUIHandle ) {
+      // Not yet dragging.
+      unsigned updateFlags = mMouseOverUpdateFlags;
+
+      // First check whether crossing cell to cell
+      if ( newCell == oldCell )
+         oldCell.reset();
+      else {
+         // Forget old targets
+         ClearTargets();
+         // Re-draw any highlighting
+         if (oldCell) {
+            ProcessUIHandleResult(
+               this, GetRuler(), oldTrack.get(), oldTrack.get(), updateFlags);
+         }
       }
-      
+
-      if (pCursor != NULL || tip != wxString())
+      // Now do the
-         mListener->TP_DisplayStatusMessage(tip);
+      // UIHANDLE HIT TEST !
+      result = newCell->HitTest(tpmState, GetProject());
+      handle = result.handle;
+
+      mLastCell = newCell;
+      mLastHitTestValid = true;
+      mLastHitTest = result;
+
+      if (!oldCell && oldHandle != handle)
+         // Did not move cell to cell, but did change the target
+         refreshCode = updateFlags;
    }
+
+   // UIHANDLE PREVIEW
+   // Update status message and cursor, whether dragging or not
+   if (handle) {
+      auto preview = handle->Preview( tpmState, GetProject() );
+      tip = preview.message;
+      pCursor = preview.cursor;
+      auto code = handle->GetChangeHighlight();
+      handle->SetChangeHighlight(RefreshCode::RefreshNone);
+      refreshCode |= code;
+      mMouseOverUpdateFlags |= code;
+   }
+   mListener->TP_DisplayStatusMessage(tip);
+   if (pCursor)
+      SetCursor( *pCursor );
+
+   ProcessUIHandleResult(
+      this, GetRuler(), newTrack.get(), newTrack.get(), refreshCode);
 }
 
 void TrackPanel::UpdateSelectionDisplay()
@@ -1238,7 +1282,8 @@ void TrackPanel::HandleWheelRotation( TrackPanelMouseEvent &tpmEvent )
    unsigned result =
       pCell->HandleWheelRotation( tpmEvent, GetProject() );
    auto pTrack = static_cast<CommonTrackPanelCell*>(pCell.get())->FindTrack();
-   ProcessUIHandleResult(this, mRuler, pTrack.get(), pTrack.get(), result);
+   ProcessUIHandleResult(
+      this, mRuler, pTrack.get(), pTrack.get(), result);
 }
 
 /// Filter captured keys typed into LabelTracks.
@@ -1361,6 +1406,8 @@ void TrackPanel::OnKeyUp(wxKeyEvent & event)
 /// Should handle the case when the mouse capture is lost.
 void TrackPanel::OnCaptureLost(wxMouseCaptureLostEvent & WXUNUSED(event))
 {
+   ClearTargets();
+   
    wxMouseEvent e(wxEVT_LEFT_UP);
 
    e.m_x = mMouseMostRecentX;
@@ -1436,6 +1483,9 @@ try
 
    if (event.Leaving())
    {
+      if ( !mUIHandle )
+         ClearTargets();
+
       auto buttons =
          // Bug 1325: button state in Leaving events is unreliable on Mac.
          // Poll the global state instead.
@@ -1463,32 +1513,32 @@ try
             mUIHandle->Drag( tpmEvent, GetProject() );
          ProcessUIHandleResult
             (this, mRuler, pClickedTrack.get(), pTrack.get(), refreshResult);
+         mMouseOverUpdateFlags |= refreshResult;
          if (refreshResult & RefreshCode::Cancelled) {
             // Drag decided to abort itself
-            mUIHandle.reset();
+            mUIHandle.reset(), ClearTargets();
             mpClickedTrack.reset();
             Uncapture( &event );
          }
          else {
-            TrackPanelMouseState tpmState{
+            UpdateMouseState(event);
-               tpmEvent.event,
+            TrackPanelMouseState tpmState{ mLastMouseState, rect, pCell };
-               tpmEvent.rect,
+            HandleMotion( tpmState );
-               tpmEvent.pCell
-            };
-            HandleCursor( tpmState );
          }
       }
       else if (event.ButtonUp()) {
          // UIHANDLE RELEASE
          auto uiHandle = mUIHandle;
-         // Null this pointer out first before calling Release -- because on Windows, we can
+         // Null mUIHandle out first before calling Release -- because on Windows, we can
          // come back recursively to this place during handling of the context menu,
          // because of a capture lost event.
-         mUIHandle.reset();
+         unsigned moreFlags = mMouseOverUpdateFlags;
+         mUIHandle.reset(), ClearTargets();
          UIHandle::Result refreshResult =
             uiHandle->Release( tpmEvent, GetProject(), this );
          ProcessUIHandleResult
-            (this, mRuler, pClickedTrack.get(), pTrack.get(), refreshResult);
+            (this, mRuler, pClickedTrack.get(), pTrack.get(),
+             refreshResult | moreFlags);
          mpClickedTrack.reset();
          // will also Uncapture() below
       }
@@ -1498,7 +1548,7 @@ try
       // consider it not a drag, even if button is down during motion, if
       // mUIHandle is null, as it becomes during interrupted drag
       // (e.g. by hitting space to play while dragging an envelope point)
-      HandleCursor( &event );
+      HandleMotion( &event );
    else if ( event.ButtonDown() || event.ButtonDClick() )
       HandleClick( tpmEvent );
 
@@ -1538,32 +1588,44 @@ void TrackPanel::HandleClick( const TrackPanelMouseEvent &tpmEvent )
    const auto &rect = tpmEvent.rect;
    auto pTrack = static_cast<CommonTrackPanelCell *>( pCell.get() )->FindTrack();
 
-   if ( !mUIHandle && pCell ) {
+   // Do hit test once more, in case the button really pressed was not the
+   // one "anticipated."
+   {
       TrackPanelMouseState tpmState{
          tpmEvent.event,
          tpmEvent.rect,
          tpmEvent.pCell
       };
-      mUIHandle =
+      HandleMotion( tpmState );
-         pCell->HitTest( tpmState, GetProject() ).handle;
    }
 
+   auto target = Target();
+   if (target)
+      mUIHandle = target->handle;
+   else
+      mUIHandle = {};
+
    if (mUIHandle) {
       // UIHANDLE CLICK
       UIHandle::Result refreshResult =
          mUIHandle->Click( tpmEvent, GetProject() );
       if (refreshResult & RefreshCode::Cancelled)
-         mUIHandle.reset();
+         mUIHandle.reset(), ClearTargets();
-      else
+      else {
          mpClickedTrack = pTrack;
-      ProcessUIHandleResult
+
-         (this, mRuler, pTrack.get(), pTrack.get(), refreshResult);
+         // Perhaps the clicked handle wants to update cursor and state message
-      TrackPanelMouseState tpmState{
+         // after a click.
-         tpmEvent.event,
+         TrackPanelMouseState tpmState{
-         tpmEvent.rect,
+            tpmEvent.event,
-         tpmEvent.pCell
+            tpmEvent.rect,
-      };
+            tpmEvent.pCell
-      HandleCursor( tpmState );
+         };
+         HandleMotion( tpmState );
+      }
+      ProcessUIHandleResult(
+         this, mRuler, pTrack.get(), pTrack.get(), refreshResult);
+      mMouseOverUpdateFlags |= refreshResult;
    }
 }
 
@@ -1574,6 +1636,9 @@ double TrackPanel::GetMostRecentXPos()
 
 void TrackPanel::RefreshTrack(Track *trk, bool refreshbacking)
 {
+   if (!trk)
+      return;
+
    Track *link = trk->GetLink();
 
    if (link && !trk->GetLinked()) {

src/TrackPanel.h

@@ -18,6 +18,8 @@
 
 #include "Experimental.h"
 
+#include "HitTestResult.h"
+
 #include "SelectedRegion.h"
 
 #include "widgets/OverlayPanel.h"
@@ -373,8 +375,8 @@ protected:
    };
    FoundCell FindCell(int mouseX, int mouseY);
 
-   void HandleCursor( wxMouseState *pState );
+   void HandleMotion( wxMouseState *pState );
-   void HandleCursor( const TrackPanelMouseState &tpmState );
+   void HandleMotion( const TrackPanelMouseState &tpmState );
 
    // If label, rectangle includes track control panel only.
    // If !label, rectangle includes all of that, and the vertical ruler, and
@@ -528,6 +530,31 @@ protected:
    wxSize vrulerSize;
 
  protected:
+   std::weak_ptr<TrackPanelCell> mLastCell;
+   HitTestResult mLastHitTest{};
+   bool mLastHitTestValid{};
+   unsigned mMouseOverUpdateFlags{};
+
+ public:
+   HitTestResult *Target()
+   {
+      if ( mLastHitTestValid )
+         return &mLastHitTest;
+      else
+         return nullptr;
+   }
+
+ protected:
+   void ClearTargets()
+   {
+      // Forget the rotation of hit test candidates when the mouse moves from
+      // cell to cell or outside of the TrackPanel entirely.
+      mLastCell.reset();
+      mLastHitTestValid = false;
+      mLastHitTest = {};
+      mMouseOverUpdateFlags = 0;
+   }
+
    std::weak_ptr<Track> mpClickedTrack;
    UIHandlePtr mUIHandle;
 

src/UIHandle.h

@@ -60,7 +60,9 @@ public:
    virtual Result Drag
       (const TrackPanelMouseEvent &event, AudacityProject *pProject) = 0;
 
-   // Update the cursor and status message.
+   // Can be called when the handle has been hit but not yet clicked,
+   // or called after Drag().
+   // Specifies cursor and status bar message.
    virtual HitTestPreview Preview
       (const TrackPanelMouseState &state, const AudacityProject *pProject) = 0;
 
@@ -99,11 +101,35 @@ public:
    // to avoid dangling pointers to tracks.  But maybe there will be a future
    // use?
    virtual void OnProjectChange(AudacityProject *pProject);
+
+public:
+   Result GetChangeHighlight() const { return mChangeHighlight; }
+   void SetChangeHighlight(Result val) { mChangeHighlight = val; }
+
+   // If AssignUIHandlePtr is used, then this function is also called before any
+   // overwrite.
+   // Make overloads of this for other subclasses, to cause refresh
+   // of the cell during mouse motion within it.
+   static UIHandle::Result NeedChangeHighlight
+   (const UIHandle &/*oldState*/, const UIHandle &/*newState*/)
+   {
+      return 0;
+   }
+
+protected:
+   // Derived classes can set this nonzero in a constructor, which is enough
+   // to cause repaint of the cell whenever the pointer hits the target,
+   // or leaves it without clicking, or releases or escapes from a drag.
+   Result mChangeHighlight { 0 };
+
 };
 
 using UIHandlePtr = std::shared_ptr<UIHandle>;
 
-// A frequent convenience
+// A frequent convenience for defining a hit test.
+// Construct a NEW handle as if hit the first time; then either keep it, or
+// use it to overwrite the state of a previously constructed handle that has not
+// yet been released.
 template<typename Subclass>
 std::shared_ptr<Subclass> AssignUIHandlePtr
 ( std::weak_ptr<Subclass> &holder, const std::shared_ptr<Subclass> &pNew )
@@ -118,7 +144,9 @@ std::shared_ptr<Subclass> AssignUIHandlePtr
       return pNew;
    }
    else {
+      auto code = Subclass::NeedChangeHighlight( *ptr, *pNew );
       *ptr = std::move(*pNew);
+      ptr->SetChangeHighlight( code );
       return ptr;
    }
 }

src/tracks/labeltrack/ui/LabelGlyphHandle.cpp

@@ -24,23 +24,32 @@ Paul Licameli split from TrackPanel.cpp
 #include <wx/translation.h>
 
 LabelGlyphHandle::LabelGlyphHandle
-(const std::shared_ptr<LabelTrack> &pLT, const wxRect &rect)
+(const std::shared_ptr<LabelTrack> &pLT,
+ const wxRect &rect, const LabelTrackHit &hit)
    : mpLT{ pLT }
    , mRect{ rect }
-{}
+   , mHit{ hit }
+{
+   mChangeHighlight = RefreshCode::RefreshCell;
+}
 
-HitTestPreview LabelGlyphHandle::HitPreview
+UIHandle::Result LabelGlyphHandle::NeedChangeHighlight
-(bool hitCenter, unsigned refreshResult)
+(const LabelGlyphHandle &oldState, const LabelGlyphHandle &newState)
+{
+   if (oldState.mHit.mEdge != newState.mHit.mEdge)
+      // pointer moves between the circle and the chevron
+      return RefreshCode::RefreshCell;
+   return 0;
+}
+
+HitTestPreview LabelGlyphHandle::HitPreview(bool hitCenter)
 {
    static wxCursor arrowCursor{ wxCURSOR_ARROW };
    return {
       (hitCenter
          ? _("Drag one or more label boundaries.")
          : _("Drag label boundary.")),
-      &arrowCursor,
+      &arrowCursor
-      // Unusually, can have a non-zero third member of HitTestPreview, so that
-      // mouse-over highlights it.
-      refreshResult
    };
 }
 
@@ -49,39 +58,22 @@ HitTestResult LabelGlyphHandle::HitTest
  const wxMouseState &state,
  const std::shared_ptr<LabelTrack> &pLT, const wxRect &rect)
 {
-   using namespace RefreshCode;
+   LabelTrackHit hit{};
-   unsigned refreshResult = RefreshNone;
+   pLT->OverGlyph(hit, state.m_x, state.m_y);
-
-   // Note: this has side effects on pLT!
-   int edge = pLT->OverGlyph(state.m_x, state.m_y);
-
-   //KLUDGE: We refresh the whole Label track when the icon hovered over
-   //changes colouration.  Inefficient.
-   edge += pLT->mbHitCenter ? 4 : 0;
-   if (edge != pLT->mOldEdge)
-   {
-      pLT->mOldEdge = edge;
-      refreshResult |= RefreshCell;
-   }
 
    // IF edge!=0 THEN we've set the cursor and we're done.
    // signal this by setting the tip.
-   if (edge != 0)
+   if ( hit.mEdge & 3 )
    {
-      auto result = std::make_shared<LabelGlyphHandle>( pLT, rect );
+      auto result = std::make_shared<LabelGlyphHandle>( pLT, rect, hit );
       result = AssignUIHandlePtr(holder, result);
       return {
-         HitPreview(pLT->mbHitCenter, refreshResult),
+         HitPreview( hit.mEdge & 4 ),
          result
       };
    }
-   else {
+
-      // An empty result, except maybe, unusually, the refresh
+   return {};
-      return {
-         { wxString{}, nullptr, refreshResult },
-         {}
-      };
-   }
 }
 
 LabelGlyphHandle::~LabelGlyphHandle()
@@ -96,9 +88,10 @@ UIHandle::Result LabelGlyphHandle::Click
    const wxMouseEvent &event = evt.event;
 
    ViewInfo &viewInfo = pProject->GetViewInfo();
-   mpLT->HandleGlyphClick(event, mRect, viewInfo, &viewInfo.selectedRegion);
+   mpLT->HandleGlyphClick
+      (mHit, event, mRect, viewInfo, &viewInfo.selectedRegion);
 
-   if (! mpLT->IsAdjustingLabel() )
+   if (! mHit.mIsAdjustingLabel )
    {
       // The positive hit test should have ensured otherwise
       //wxASSERT(false);
@@ -125,7 +118,8 @@ UIHandle::Result LabelGlyphHandle::Drag
 
    const wxMouseEvent &event = evt.event;
    ViewInfo &viewInfo = pProject->GetViewInfo();
-   mpLT->HandleGlyphDragRelease(event, mRect, viewInfo, &viewInfo.selectedRegion);
+   mpLT->HandleGlyphDragRelease
+      (mHit, event, mRect, viewInfo, &viewInfo.selectedRegion);
 
    // Refresh all so that the change of selection is redrawn in all tracks
    return result | RefreshCode::RefreshAll | RefreshCode::DrawOverlays;
@@ -134,7 +128,7 @@ UIHandle::Result LabelGlyphHandle::Drag
 HitTestPreview LabelGlyphHandle::Preview
 (const TrackPanelMouseState &, const AudacityProject *)
 {
-   return HitPreview(mpLT->mbHitCenter, 0);
+   return HitPreview( mHit.mEdge & 4 );
 }
 
 UIHandle::Result LabelGlyphHandle::Release
@@ -142,11 +136,11 @@ UIHandle::Result LabelGlyphHandle::Release
  wxWindow *pParent)
 {
    auto result = LabelDefaultClickHandle::Release( evt, pProject, pParent );
-   mpLT->mOldEdge = 0;
 
    const wxMouseEvent &event = evt.event;
    ViewInfo &viewInfo = pProject->GetViewInfo();
-   if (mpLT->HandleGlyphDragRelease(event, mRect, viewInfo, &viewInfo.selectedRegion)) {
+   if (mpLT->HandleGlyphDragRelease
+          (mHit, event, mRect, viewInfo, &viewInfo.selectedRegion)) {
       pProject->PushState(_("Modified Label"),
          _("Label Edit"),
          UndoPush::CONSOLIDATE);
@@ -158,7 +152,6 @@ UIHandle::Result LabelGlyphHandle::Release
 
 UIHandle::Result LabelGlyphHandle::Cancel(AudacityProject *pProject)
 {
-   mpLT->mOldEdge = 0;
    pProject->RollbackState();
    auto result = LabelDefaultClickHandle::Cancel( pProject );
    return result | RefreshCode::RefreshAll;

src/tracks/labeltrack/ui/LabelGlyphHandle.h

@@ -19,14 +19,33 @@ class wxMouseState;
 struct HitTestResult;
 class LabelTrack;
 
+/// mEdge:
+/// 0 if not over a glyph,
+/// else a bitwise or of :
+/// 1 if over the left-hand glyph,
+/// 2 if over the right-hand glyph on a label,
+/// 4 if over center.
+///
+///   mMouseLabelLeft - index of any left label hit
+///   mMouseLabelRight - index of any right label hit
+///
+struct LabelTrackHit {
+   int mEdge{};
+   int mMouseOverLabelLeft{ -1 };    /// Keeps track of which left label the mouse is currently over.
+   int mMouseOverLabelRight{ -1 };   /// Keeps track of which right label the mouse is currently over.
+   bool mbIsMoving {};
+   bool mIsAdjustingLabel {};
+};
+
 class LabelGlyphHandle final : public LabelDefaultClickHandle
 {
    LabelGlyphHandle(const LabelGlyphHandle&) = delete;
-   static HitTestPreview HitPreview(bool hitCenter, unsigned refreshResult);
+   static HitTestPreview HitPreview(bool hitCenter);
 
 public:
    explicit LabelGlyphHandle
-      (const std::shared_ptr<LabelTrack> &pLT, const wxRect &rect);
+      (const std::shared_ptr<LabelTrack> &pLT,
+       const wxRect &rect, const LabelTrackHit &hit);
 
    LabelGlyphHandle &operator=(LabelGlyphHandle&&) = default;
    
@@ -55,6 +74,11 @@ public:
 
    bool StopsOnKeystroke() override { return true; }
 
+   LabelTrackHit mHit{};
+
+   static UIHandle::Result NeedChangeHighlight
+      (const LabelGlyphHandle &oldState, const LabelGlyphHandle &newState);
+
 private:
    std::shared_ptr<LabelTrack> mpLT {};
    wxRect mRect {};

src/tracks/labeltrack/ui/LabelTrackUI.cpp

@@ -31,13 +31,11 @@ HitTestResult LabelTrack::DetailedHitTest
    // Try label movement handles first
    result = LabelGlyphHandle::HitTest(
       mGlyphHandle, state, Pointer<LabelTrack>(this), st.rect);
-   auto refresh = result.preview.refreshCode; // kludge
 
    if ( !result.handle ) {
       // Missed glyph, try text box
       result = LabelTextHandle::HitTest(
          mTextHandle, state, Pointer<LabelTrack>(this));
-      result.preview.refreshCode |= refresh; // kludge
    }
 
    return result;

src/tracks/ui/TrackUI.cpp

@@ -46,9 +46,6 @@ HitTestResult Track::HitTest
    // If there is no detailed hit for the subclass, there are still some
    // general cases.
 
-   // Label track kludge!
-   auto refresh = result.preview.refreshCode;
-
    // Sliding applies in more than one track type.
    if ( !result.handle && !isMultiTool && currentTool == slideTool )
       result = TimeShiftHandle::HitAnywhere(
@@ -65,7 +62,6 @@ HitTestResult Track::HitTest
       result = SelectHandle::HitTest(
          mSelectHandle, st, pProject, Pointer(this));
 
-   result.preview.refreshCode |= refresh;
    return result;
 }