Accessibility: clean up track focus events after an effect is applied.

Problem. When an effect is applied, whatever track is the original focus, there is a focus event for track one. This causes NVDA to read out the track name of track 1, which is unnecessary noise.
The reason for this is that the execution of the Progress dialog destructor causes AudacityProject::OnActivate() to be called which causes a set focus on the TrackPanel. When this happens, the pointers to the selected tracks have changed, but the final focus has not been set (at the end of AudacityProject::DoEffect()). So TrackPanelAx::GetFocus returns the first track.

Fix: Modify TrackPanelAx::GetFocus so that if the existing pointer to the focused track is null, then use the track at the same position, if it exists.

src/TrackPanelAx.cpp

@@ -40,23 +40,36 @@ TrackPanelAx::TrackPanelAx( wxWindow *window )
 
    mTrackName = true;
    mMessageCount = 0;
+   mNumFocusedTrack = 0;
 }
 
 TrackPanelAx::~TrackPanelAx()
 {
 }
 
-// Returns currently focused track or first one if none focused
+// Returns currently focused track
+// if that track no longer exists, if there is a track at
+// the same position, use that, else if there is a first
+// track, use that.
 std::shared_ptr<Track> TrackPanelAx::GetFocus()
 {
    auto focusedTrack = mFocusedTrack.lock();
    if( !focusedTrack ) {
-      TrackListIterator iter( mTrackPanel->GetTracks() );
-      focusedTrack = Track::Pointer( iter.First() );
-      // only call SetFocus if the focus has changed to avoid
-      // unnecessary focus events
-      if (focusedTrack) 
-         focusedTrack = SetFocus();
+      if (mNumFocusedTrack >=1) {
+         // This prevents the focus from being unnecessarily set to track 1
+         // when effects are applied. (Applying an effect can change
+         // the pointers of the selected tracks.)
+         focusedTrack = FindTrack(mNumFocusedTrack);
+      }
+      if (!focusedTrack) {
+
+         TrackListIterator iter( mTrackPanel->GetTracks() );
+         focusedTrack = Track::Pointer( iter.First() );
+         // only call SetFocus if the focus has changed to avoid
+         // unnecessary focus events
+         if (focusedTrack) 
+            focusedTrack = SetFocus();
+      }
    }
 
    if( !TrackNum( focusedTrack ) )
@@ -92,23 +105,22 @@ std::shared_ptr<Track> TrackPanelAx::SetFocus( std::shared_ptr<Track> track )
    }
 
    mFocusedTrack = track;
+   mNumFocusedTrack = TrackNum(track);
 
 #if wxUSE_ACCESSIBILITY
    if( track )
    {
-      int num = TrackNum( track );
-
       NotifyEvent( wxACC_EVENT_OBJECT_FOCUS,
                    mTrackPanel,
                    wxOBJID_CLIENT,
-                   num );
+                   mNumFocusedTrack );
 
       if( track->GetSelected() )
       {
          NotifyEvent( wxACC_EVENT_OBJECT_SELECTION,
                       mTrackPanel,
                       wxOBJID_CLIENT,
-                      num );
+                      mNumFocusedTrack );
       }
    }
    else

src/TrackPanelAx.h

@@ -121,6 +121,7 @@ private:
    TrackPanel *mTrackPanel;
 
    std::weak_ptr<Track> mFocusedTrack;
+   int mNumFocusedTrack;
 
    wxString mMessage;
    bool mTrackName;