Tweaks to names on tracks

This makes them opaque when the track height is low.
It also improves on painting with low stereo tracks, where the name previously was clipped.

src/TrackArtist.cpp

@@ -48,6 +48,7 @@ audio tracks.
 #include <math.h>
 #include <float.h>
 #include <limits>
+#include <wx/utils.h>
 
 #ifdef HAVE_ALLOCA_H
 #include <alloca.h>
@@ -289,6 +290,52 @@ void TrackArt::DrawTracks(TrackPanelDrawingContext &context,
    }
 }
 
+void TrackArt::DrawTrackNames(TrackPanelDrawingContext &context,
+                              const TrackList * tracks,
+                              const wxRegion & reg,
+                              const wxRect & clip)
+{
+   // Fix the horizontal extent; will later change only the vertical extent.
+   const auto artist = TrackArtist::Get( context );
+   const auto leftOffset = artist->leftOffset;
+   wxRect teamRect{
+      clip.x + leftOffset, 0, clip.width - (leftOffset + kRightMargin), 0
+   };
+
+   const auto &zoomInfo = *artist->pZoomInfo;
+   if( !artist->mbShowTrackNameInTrack )
+      return;
+
+   for(auto leader : tracks->Leaders()) {
+      auto group = TrackList::Channels( leader );
+      leader = leader->SubstitutePendingChangedTrack().get();
+
+      teamRect.y = leader->GetY() - zoomInfo.vpos;
+      teamRect.height = group.sum( [&] (const Track *channel) {
+         channel = channel->SubstitutePendingChangedTrack().get();
+         return channel->GetHeight();
+      });
+
+      if (teamRect.GetBottom() < clip.GetTop())
+         continue;
+      else if (teamRect.GetTop() > clip.GetBottom())
+         break;
+
+      for (auto t : group) {
+         if (teamRect.Intersects(clip) && reg.Contains(teamRect)) {
+            t = t->SubstitutePendingChangedTrack().get();
+            wxRect trackRect {
+               teamRect.x,
+               t->GetY() - zoomInfo.vpos + kTopMargin,
+               teamRect.width,
+               teamRect.height
+            };
+            DrawTrackName( context, t, trackRect );
+         }
+      }
+   }
+}
+
 // Draws the track name on the track, if it is needed.
 void TrackArt::DrawTrackName( TrackPanelDrawingContext &context, const Track * t, const wxRect & rect )
 {
@@ -304,10 +351,24 @@ void TrackArt::DrawTrackName( TrackPanelDrawingContext &context, const Track * t
    dc.SetFont(labelFont);
    dc.GetTextExtent( t->GetName(), &x, &y );
 
+   // Logic for name background translucency (aka 'shields')
+   // Tracks less than kOpaqueHeight high will have opaque shields.
+   // Tracks more than kTranslucentHeight will have maximum translucency for shields.
+   const int kOpaqueHeight = 44;
+   const int kTranslucentHeight = 124;
+   int h = rect.GetHeight();
+   // f codes the opacity as a number between 0.0 and 1.0
+   float f= wxClip((h -kOpaqueHeight)/(float)(kTranslucentHeight-kOpaqueHeight),0.0,1.0);
+   // kOpaque is the shield's alpha for tracks that are not tall
+   // kTranslucent is the shield's alpha for tracks that are tall.
+   const int kOpaque = 255;
+   const int kTranslucent = 140;
+   // 0.0 maps to full opacity, 1.0 maps to full translucency.
+   int opacity = 255 - (255-140)*f;
+
 #ifdef __WXMAC__
    // Mac dc is a graphics dc already.
-   // Shield's background is translucent, alpha=140
-   AColor::UseThemeColour( &dc, clrTrackInfoSelected, clrTrackPanelText, 140 );
+   AColor::UseThemeColour( &dc, clrTrackInfoSelected, clrTrackPanelText, opacity );
    dc.DrawRoundedRectangle( rect.x+7, rect.y+1,  x+16, y+4, 8.0 );
 #else
    // This little dance with wxImage in order to draw to a graphic dc
@@ -318,8 +379,8 @@ void TrackArt::DrawTrackName( TrackPanelDrawingContext &context, const Track * t
    memset(alpha, wxIMAGE_ALPHA_TRANSPARENT, image.GetWidth()*image.GetHeight());
     
    wxGraphicsContext &gc=*wxGraphicsContext::Create(image);
-   // Shield's background is translucent, alpha=140.  This is to a gc, not a dc.
-   AColor::UseThemeColour( &gc, clrTrackInfoSelected, clrTrackPanelText, 140 );
+   // This is to a gc, not a dc.
+   AColor::UseThemeColour( &gc, clrTrackInfoSelected, clrTrackPanelText, opacity );
    // Draw at 1,1, not at 0,0 to avoid clipping of the antialiasing.
    gc.DrawRoundedRectangle( 1, 1,  x+16, y+4, 8.0 );
    // delete the gc so as to free and so update the wxImage.
@@ -386,8 +447,6 @@ void TrackArt::DrawTrack(TrackPanelDrawingContext &context,
          DrawTimeTrack( context, tt, rect );
       }
    );
-   if( artist->mbShowTrackNameInTrack )
-      DrawTrackName( context, t, rect );
 }
 
 void TrackArt::DrawVRuler

src/TrackArtist.h

@@ -61,6 +61,11 @@ namespace TrackArt {
    void DrawVRuler(TrackPanelDrawingContext &context,
                    const Track *t, const wxRect & rect, bool bSelected );
    
+   void DrawTrackNames(TrackPanelDrawingContext &context,
+                       const TrackList *tracks,
+                       const wxRegion & reg,
+                       const wxRect &clip);
+
    void DrawTrackName(TrackPanelDrawingContext &context, 
                       const Track *t, const wxRect & rect );
 

src/TrackPanel.cpp

@@ -1093,6 +1093,7 @@ void TrackPanel::DrawTracks(wxDC * dc)
    // Draw the rest, including the click-to-deselect blank area below all
    // tracks
    DrawEverythingElse(context, region, clip);
+   TrackArt::DrawTrackNames( context, GetTracks(), region, clip );
 }
 
 /// Draws 'Everything else'.  In particular it draws: