Do without some friend declarations in LabelTrack...

... and leave "updated" alone, it's only for use in interactive dragging

src/LabelTrack.cpp

@@ -148,6 +148,15 @@ LabelTrack::LabelTrack(const LabelTrack &orig) :
    ResetFlags();
 }
 
+void LabelTrack::SetLabel( size_t iLabel, const LabelStruct &newLabel )
+{
+   if( iLabel >= mLabels.size() ) {
+      wxASSERT( false );
+      mLabels.resize( iLabel + 1 );
+   }
+   mLabels[ iLabel ] = newLabel;
+}
+
 LabelTrack::~LabelTrack()
 {
 }
@@ -937,6 +946,14 @@ void LabelTrack::Draw
    }
 }
 
+void LabelTrack::SetSelectedIndex( int index )
+{
+   if ( index >= 0 && index < mLabels.size() )
+      mSelIndex = index;
+   else
+      mSelIndex = -1;
+}
+
 /// uses GetTextExtent to find the character position
 /// corresponding to the x pixel position.
 int LabelTrack::FindCurrentCursorPosition(int xPos)

src/LabelTrack.h

@@ -38,6 +38,7 @@ struct TrackPanelDrawingContext;
 class LabelStruct
 {
 public:
+   LabelStruct() = default;
    // Copies region
    LabelStruct(const SelectedRegion& region, const wxString &aTitle);
    // Copies region but then overwrites other times
@@ -84,15 +85,15 @@ public:
 public:
    SelectedRegion selectedRegion;
    wxString title; /// Text of the label.
-   mutable int width; /// width of the text in pixels.
+   mutable int width{}; /// width of the text in pixels.
 
 // Working storage for on-screen layout.
-   mutable int x;     /// Pixel position of left hand glyph
+   mutable int x{};     /// Pixel position of left hand glyph
-   mutable int x1;    /// Pixel position of right hand glyph
+   mutable int x1{};    /// Pixel position of right hand glyph
-   mutable int xText; /// Pixel position of left hand side of text box
+   mutable int xText{}; /// Pixel position of left hand side of text box
-   mutable int y;     /// Pixel position of label.
+   mutable int y{};     /// Pixel position of label.
 
-   bool updated;                  /// flag to tell if the label times were updated
+   bool updated{};                  /// flag to tell if the label times were updated
 };
 
 using LabelArray = std::vector<LabelStruct>;
@@ -121,6 +122,8 @@ class AUDACITY_DLL_API LabelTrack final : public Track
 
    virtual ~ LabelTrack();
 
+   void SetLabel( size_t iLabel, const LabelStruct &newLabel );
+
    void SetOffset(double dOffset) override;
 
    static const int DefaultFontSize = 12;
@@ -131,6 +134,7 @@ class AUDACITY_DLL_API LabelTrack final : public Track
    void Draw( TrackPanelDrawingContext &context, const wxRect & r ) const;
 
    int GetSelectedIndex() const;
+   void SetSelectedIndex( int index );
 
    double GetOffset() const override;
    double GetStartTime() const override;
@@ -297,9 +301,6 @@ private:
 protected:
    std::shared_ptr<TrackView> DoGetView() override;
    std::shared_ptr<TrackControls> DoGetControls() override;
-
-   friend class GetInfoCommand; // to get labels.
-   friend class SetLabelCommand; // to set labels.
 };
 
 #endif

src/commands/GetInfoCommand.cpp

@@ -610,8 +610,7 @@ bool GetInfoCommand::SendLabels(const CommandContext &context)
          context.StartArray();
          context.AddItem( (double)i ); // Track number.
          context.StartArray();
-         for (int nn = 0; nn< (int)labelTrack->mLabels.size(); nn++) {
+         for ( const auto &label : labelTrack->GetLabels() ) {
-            const auto &label = labelTrack->mLabels[nn];
             context.StartArray();
             context.AddItem( label.getT0() ); // start
             context.AddItem( label.getT1() ); // end

src/commands/SetLabelCommand.cpp

@@ -68,49 +68,50 @@ bool SetLabelCommand::Apply(const CommandContext & context)
    AudacityProject * p = &context.project;
    auto &tracks = TrackList::Get( *p );
    auto &selectedRegion = ViewInfo::Get( *p ).selectedRegion;
-   LabelStruct * pLabel = NULL;
+   const LabelStruct * pLabel = nullptr;
-   int i=0;
+   LabelTrack *labelTrack = nullptr;
-   int nn=0;
+   auto ii = mLabelIndex;
-
+   if ( mLabelIndex >= 0 ) {
-   LabelTrack *labelTrack {};
       for (auto lt : tracks.Any<LabelTrack>()) {
-      if( i > mLabelIndex )
+         const auto &labels = lt->GetLabels();
-         break;
+         const auto nLabels = labels.size();
+         if( ii >= nLabels )
+            ii -= nLabels;
+         else {
             labelTrack = lt;
-      for (nn = 0;
+            pLabel = &labels[ ii ];
-         (nn< (int)labelTrack->mLabels.size()) && i<=mLabelIndex; 
+            break;
-         nn++) {
+         }
-         i++;
-         pLabel = &labelTrack->mLabels[nn];
       }
    }
 
-   if ( (i< mLabelIndex) || (pLabel == NULL))
+   if ( !pLabel )
    {
       context.Error(wxT("LabelIndex was invalid."));
       return false;
    }
+   auto newLabel = *pLabel;
    if( bHasText )
-      pLabel->title = mText;
+      newLabel.title = mText;
    if( bHasT0 )
-      pLabel->selectedRegion.setT0(mT0, false);
+      newLabel.selectedRegion.setT0(mT0, false);
    if( bHasT1 )
-      pLabel->selectedRegion.setT1(mT1, false);
+      newLabel.selectedRegion.setT1(mT1, false);
    if( bHasT0 || bHasT1 )
-      pLabel->selectedRegion.ensureOrdering();
+      newLabel.selectedRegion.ensureOrdering();
-   pLabel->updated = true;
+   labelTrack->SetLabel( ii, newLabel );
 
    // Only one label can be selected.
    if( bHasSelected ) {
       if( mbSelected )
       {
-         labelTrack->mSelIndex = nn-1;
+         labelTrack->SetSelectedIndex( ii );
          double t0 = pLabel->selectedRegion.t0();
          double t1 = pLabel->selectedRegion.t1();
          selectedRegion.setTimes( t0, t1);
       }
-      else if( labelTrack->mSelIndex == (nn-1) )
+      else if( labelTrack->GetSelectedIndex() == ii )
-         labelTrack->mSelIndex = -1;
+         labelTrack->SetSelectedIndex( -1 );
    }
 
    labelTrack->SortLabels();

src/commands/SetLabelCommand.h

@@ -37,6 +37,8 @@ public:
    bool Apply(const CommandContext & context) override;
 
 public:
+   // zero-based index of the desired label, within the concatenation of the
+   // arrays of labels of all label tracks
    int mLabelIndex;
    wxString mText;
    double mT0;