Hide details of screenshot rectangle computations in TrackPanel

(cherry picked from audacity commit 8cbad2022817650f30e737247fa6e6dc25069b81)

Signed-off-by: akleja <storspov@gmail.com>

src/TrackPanel.cpp

@@ -1542,7 +1542,7 @@ wxRect TrackPanel::FindTrackRect( const Track * target )
 {
    auto leader = *GetTracks()->FindLeader( target );
    if (!leader) {
-      return { 0, 0, 0, 0 };
+      return {};
    }
 
    return CellularPanel::FindRect( [&] ( TrackPanelNode &node ) {
@@ -1552,6 +1552,34 @@ wxRect TrackPanel::FindTrackRect( const Track * target )
    } );
 }
 
+wxRect TrackPanel::FindFocusedTrackRect( const Track * target )
+{
+   auto rect = FindTrackRect(target);
+   if (rect != wxRect{}) {
+      // Enlarge horizontally.
+      // PRL:  perhaps it's one pixel too much each side, including some gray
+      // beyond the yellow?
+      rect.x = 0;
+      GetClientSize(&rect.width, nullptr);
+
+      // Enlarge vertically, enough to enclose the yellow focus border pixels
+      // The the outermost ring of gray pixels is included on three sides
+      // but not the top (should that be fixed?)
+
+      // (Note that TrackPanel paints its focus over the "top margin" of the
+      // rectangle allotted to the track, according to TrackView::GetY() and
+      // TrackView::GetHeight(), but also over the margin of the next track.)
+
+      rect.height += kBottomMargin;
+      int dy = kTopMargin - 1;
+      rect.Inflate( 0, dy );
+
+      // Note that this rectangle does not coincide with any one of
+      // the nodes in the subdivision.
+   }
+   return rect;
+}
+
 TrackPanelCell *TrackPanel::GetFocusedCell()
 {
    auto pTrack = TrackFocus::Get( *GetProject() ).Get();

src/TrackPanel.h

@@ -135,10 +135,20 @@ protected:
 public:
    void MakeParentRedrawScrollbars();
 
-   // Rectangle includes track control panel, and the vertical ruler, and
-   // the proper track area of all channels, and the separators between them.
+   /*!
+    @return includes track control panel, and the vertical ruler, and
+    the proper track area of all channels, and the separators between them.
+    If target is nullptr, returns empty rectangle.
+   */
    wxRect FindTrackRect( const Track * target );
 
+   /*!
+    @return includes what's in `FindTrackRect(target)` and the focus ring
+    area around it.
+    If target is nullptr, returns empty rectangle.
+   */
+   wxRect FindFocusedTrackRect( const Track * target );
+
 protected:
    // Get the root object defining a recursive subdivision of the panel's
    // area into cells

src/commands/ScreenshotCommand.cpp

@@ -708,27 +708,7 @@ wxRect ScreenshotCommand::GetTracksRect(TrackPanel * panel){
 wxRect ScreenshotCommand::GetTrackRect( AudacityProject * pProj, TrackPanel * panel, int n){
    auto FindRectangle = []( TrackPanel &panel, Track &t )
    {
-      // This rectangle omits the focus ring about the track, and
-      // also within that, a narrow black border with a "shadow" below and
-      // to the right
-      wxRect rect = panel.FindTrackRect( &t );
-
-      // Enlarge horizontally.
-      // PRL:  perhaps it's one pixel too much each side, including some gray
-      // beyond the yellow?
-      rect.x = 0;
-      panel.GetClientSize(&rect.width, nullptr);
-
-      // Enlarge vertically, enough to enclose the yellow focus border pixels
-      // Omit the outermost ring of gray pixels
-
-      // (Note that TrackPanel paints its focus over the "top margin" of the
-      // rectangle allotted to the track, according to TrackView::GetY() and
-      // TrackView::GetHeight(), but also over the margin of the next track.)
-
-      rect.height += kBottomMargin;
-      int dy = kTopMargin - 1;
-      rect.Inflate( 0, dy );
+      wxRect rect = panel.FindFocusedTrackRect( &t );
 
       // Reposition it relative to parent of panel
       rect.SetPosition(