When painting a widget...

  window->get_geometry(winx, winy, winw, winh, wind);

...is not the proper way to retrieve the area of where to paint.
This is the correct way:

  GtkAllocation alloc = get_allocation()

This was causing the missing 3D border around various windows.

Perhaps this is already clear, but just in case: draw(0,0,w,h) should become
draw(alloc.x, alloc.y, alloc.width, alloc.height), so (0,0) is not always the
origin.

I tried this for the TimeBar. get_allocation seems to return coordinates
relative to the entire window (for the timebar in mainwindow the upper-left
corner of the mainwindow, not the upper-left corner of the timebar itself....).
TimeBar derives from DrawingArea. I assume that this Widhet has its own window
(with coordinate (0,0) and all drawing operation are relative to this.

Fixed