Bug 1671 (part 2) - Clock icons do not propagate into Sync-locked MIDI / Spectrogram view tracks

This is the second half of the bug and it does MIDI.

src/Experimental.h

@@ -58,8 +58,15 @@
 //#define EXPERIMENTAL_DA
 
 // Define this so that sync-lock tiles shine through spectrogram.
+// The spectrogram pastes a bitmap over the tiles.
+// This makes it use alpha blending, most transparent where least intense.
 #define EXPERIMENTAL_SPECTROGRAM_OVERLAY
 
+// Define this so that sync-lock tiles shine through note/MIDI track.
+// The note track then relies on the same code for drawing background as
+// Wavetrack, and draws its notes and lines over the top.
+#define EXPERIMENTAL_NOTETRACK_OVERLAY
+
 // EXPERIMENTAL_THEMING is mostly mainstream now.
 // the define is still present to mark out old code before theming, that we might
 // conceivably need.

src/TrackArtist.cpp

@@ -2817,7 +2817,9 @@ void TrackArtist::DrawNoteBackground(const NoteTrack *track, wxDC &dc,
 {
    dc.SetBrush(wb);
    dc.SetPen(wp);
+#ifndef EXPERIMENTAL_NOTETRACK_OVERLAY
    dc.DrawRectangle(sel); // fill rectangle with white keys background
+#endif
 
    int left = TIME_TO_X(track->GetOffset());
    if (left < sel.x) left = sel.x; // clip on left
@@ -2932,6 +2934,12 @@ void TrackArtist::DrawNoteTrack(const NoteTrack *track,
    // we add the height of bottomNote from the position of pitch 0
    track->PrepareIPitchToY(rect);
 
+#ifdef EXPERIMENTAL_NOTETRACK_OVERLAY
+   DrawBackgroundWithSelection(&dc, rect, track,
+         AColor::labelSelectedBrush, AColor::labelUnselectedBrush,
+         selectedRegion, zoomInfo);
+#endif
+
    // Background comes in 4 colors, that are now themed.
    //   214, 214,214 -- unselected white keys
    //   192,192,192 -- black keys