Bug 63 - Analysis effects that create labels should give focus to label Track

If a generator, effect or analyser has created a new track, scroll to the bottom of the track list.
Acheived using new function, VerticalScroll()

src/Menus.cpp

@@ -4298,6 +4298,7 @@ bool AudacityProject::OnEffect(const PluginID & ID, int flags)
 
    wxGetApp().SetMissingAliasedFileWarningShouldShow(true);
 
+   int nTracksOriginally = GetTrackCount();
    TrackListIterator iter(GetTracks());
    Track *t = iter.First();
    WaveTrack *newTrack{};
@@ -4389,9 +4390,18 @@ bool AudacityProject::OnEffect(const PluginID & ID, int flags)
    if (focus != nullptr) {
       focus->SetFocus();
    }
-   mTrackPanel->EnsureVisible(mTrackPanel->GetFirstSelectedTrack());
 
+   // A fix for Bug 63
+   // New tracks added?  Scroll them into view so that user sees them.
+   // Don't care what track type.  An analyser might just have added a
+   // Label track and we want to see it.
+   if( GetTrackCount() > nTracksOriginally ){
+      // 0.0 is min scroll position, 1.0 is max scroll position.
+      GetTrackPanel()->VerticalScroll( 1.0 );
+   }  else {
+      mTrackPanel->EnsureVisible(mTrackPanel->GetFirstSelectedTrack());
       mTrackPanel->Refresh(false);
+   }
 
    return true;
 }

src/Project.h

@@ -176,6 +176,7 @@ class AUDACITY_DLL_API AudacityProject final : public wxFrame,
 
    TrackList *GetTracks() { return mTracks.get(); }
    const TrackList *GetTracks() const { return mTracks.get(); }
+   const int GetTrackCount(){ return GetTracks()->GetCount(); }
    UndoManager *GetUndoManager() { return mUndoManager.get(); }
 
    sampleFormat GetDefaultFormat() { return mDefaultFormat; }

src/TrackPanel.cpp

@@ -2749,6 +2749,50 @@ void TrackPanel::EnsureVisible(Track * t)
    Refresh(false);
 }
 
+// 0.0 scrolls to top
+// 1.0 scrolls to bottom.
+void TrackPanel::VerticalScroll( float fracPosition){
+   TrackListIterator iter(GetTracks());
+   Track *it = NULL;
+   Track *nt = NULL;
+
+   // Compute trackHeight
+   int trackTop = 0;
+   int trackHeight =0;
+
+   for (it = iter.First(); it; it = iter.Next()) {
+      trackTop += trackHeight;
+      trackHeight =  it->GetHeight();
+
+      //find the second track if this is stereo
+      if (it->GetLinked()) {
+         nt = iter.Next();
+         trackHeight += nt->GetHeight();
+      }
+#ifdef EXPERIMENTAL_OUTPUT_DISPLAY
+      else if(MONO_WAVE_PAN(it)){
+         trackHeight += it->GetHeight(true);
+      }
+#endif
+      else {
+         nt = it;
+      }
+   }
+
+   int delta;
+   
+   //Get the size of the trackpanel.
+   int width, height;
+   GetSize(&width, &height);
+
+   delta = (fracPosition * (trackTop + trackHeight - height)) - mViewInfo->vpos + mViewInfo->scrollStep;
+   //wxLogDebug( "Scroll down by %i pixels", delta );
+   delta /= mViewInfo->scrollStep;
+   mListener->TP_ScrollUpDown(delta);
+   Refresh(false);
+}
+
+
 // Given rectangle excludes the insets left, right, and top
 // Draw a rectangular border and also a vertical separator of track controls
 // from the rest (ruler and proper track area)

src/TrackPanel.h

@@ -332,6 +332,7 @@ class AUDACITY_DLL_API TrackPanel final : public OverlayPanel {
    bool IsMouseCaptured();
 
    void EnsureVisible(Track * t);
+   void VerticalScroll( float fracPosition);
 
    Track *GetFocusedTrack();
    void SetFocusedTrack(Track *t);