This is how quodlibet preferences window looks with Ambiance gtk+ theme in MATE Desktop (marco as window manager, no-compiz). Menu icon at the left, close icon at the right.
This is how quodlibet preferences window looks with Numix gtk+ theme in MATE Desktop (marco as window manager, no-compiz). No options and close icons.
Similar thing happens with audacious preferences and equalizer windows.
This is how quodlibet preferences window looks with Ambiance gtk+ theme in MATE Desktop (marco as window manager, no-compiz). Menu icon at the left, close icon at the right.
This is how quodlibet preferences window looks with Numix gtk+ theme in MATE Desktop (marco as window manager, no-compiz). No options and close icons.
Similar thing happens with audacious preferences and equalizer windows.
Ambiance:
Numix: