Mac OS: How to make pop-up menu background transparent

I have same code which works fine on Windows and Linux but on Mac OS, the pop-up menu has a grey background and is not clipped properly:
Attachment 8585

For implementing this, i am subclassing QMenu, creating a custom QPainterPath, drawing it inside paintEvent using painter.drawPath and also using setMask().

Is this an issue with Qt? Any solution to this?

Note: In this link, please refer QGroupBox and QTabWidget screen shots, i can see the grey background as part of the widget.
http://doc.qt.digia.com/main-snapsho...macintosh.html

Anyone? Using setMask(), i am able to mask out the background on all platforms except Mac.
Also, if i set background color though style sheet, the background shows up as black

You may try to set another widget's backgorund as transparent to see whether the issue is particular to pop-up menus or not.

I just replaced the custom base class from QMenu to QWidget and the masking works properly, so apparently this issue is only coming with QMenu.
Is this a bug? Should i file a bug report?

Any ideas how to fix this issue?