Translucent background to track name (all platforms)

wxDC can draw translucently, if given a bitmap.  So we now create a suitable bitmap, using a wxGraphicsContext.

src/AColor.cpp

@@ -314,6 +314,27 @@ void AColor::UseThemeColour( wxDC * dc, int iBrush, int iPen, int alpha )
    dc->SetPen( sparePen );
 }
 
+void AColor::UseThemeColour( wxGraphicsContext * gc, int iBrush, int iPen, int alpha )
+{
+   if (!inited)
+      Init();
+   // do nothing if no colours set.
+   if( (iBrush == -1) && ( iPen ==-1))
+      return;
+   wxColour col = wxColour(0,0,0);
+   if( iBrush !=-1 ){
+      col = theTheme.Colour( iBrush );
+      col.Set( col.Red(), col.Green(), col.Blue(), alpha);
+      spareBrush.SetColour( col );
+      gc->SetBrush( spareBrush );
+   }
+   if( iPen != -1)
+      col = theTheme.Colour( iPen );
+   sparePen.SetColour( col );
+   gc->SetPen( sparePen );
+}
+
+
 void AColor::Light(wxDC * dc, bool selected, bool highlight)
 {
    if (!inited)

src/AColor.h

@@ -19,6 +19,7 @@
 #include <wx/pen.h> // member variable
 
 class wxDC;
+class wxGraphicsContext;
 class wxRect;
 
 /// Used to restore pen, brush and logical-op in a DC back to what they were.
@@ -79,6 +80,7 @@ class AColor {
    static wxColour Blend(const wxColour & c1, const wxColour & c2);
 
    static void UseThemeColour( wxDC * dc, int iBrush, int iPen=-1, int alpha = 255 );
+   static void UseThemeColour( wxGraphicsContext * gc, int iBrush, int iPen=-1, int alpha = 255 );
    static void TrackPanelBackground(wxDC * dc, bool selected);
 
    static void Light(wxDC * dc, bool selected, bool highlight = false);

src/TrackArtist.cpp

@@ -337,11 +337,31 @@ void TrackArt::DrawTrack(TrackPanelDrawingContext &context,
             wxFont labelFont(12, wxFONTFAMILY_SWISS, wxFONTSTYLE_NORMAL, wxFONTWEIGHT_NORMAL);
             dc.SetFont(labelFont);
             dc.GetTextExtent( wt->GetName(), &x, &y );
-            dc.SetTextForeground(theTheme.Colour( clrTrackPanelText ));
-            // Shield's background is translucent, alpha=100, but currently 
-            // only on mac.
-            AColor::UseThemeColour( &dc, clrTrackInfoSelected, clrTrackPanelText, 100 );
+
+#ifdef __WXMAC__
+            // Mac dc is a graphics dc already.
+            // Shield's background is translucent, alpha=180
+            AColor::UseThemeColour( &dc, clrTrackInfoSelected, clrTrackPanelText, 180 );
             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
+            // which we can then paste as a translucent bitmap onto the real dc.
+            wxImage image( x+18, y+6 );
+            image.InitAlpha();
+            unsigned char *alpha=image.GetAlpha();
+            memset(alpha, wxIMAGE_ALPHA_TRANSPARENT, image.GetWidth()*image.GetHeight());
+    
+            wxGraphicsContext &gc=*wxGraphicsContext::Create(image);
+            // Shield's background is translucent, alpha=180.  This is to a gc, not a dc.
+            AColor::UseThemeColour( &gc, clrTrackInfoSelected, clrTrackPanelText, 180 );
+            // 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.
+            delete &gc;
+            wxBitmap bitmap( image );
+            dc.DrawBitmap( bitmap, rect.x+6, rect.y);
+#endif
+            dc.SetTextForeground(theTheme.Colour( clrTrackPanelText ));
             dc.DrawText (wt->GetName(), rect.x+15, rect.y+3);  // move right 15 pixels to avoid overwriting <- symbol
          }
       },