Qt: Erase background (Windows Aero Glass)

Answer 1

Can you provide us the paint code ? Do you subclass a widget ?

Answer 2

Just use:

QPainter p

p.setCompositionMode(QPainter::CompositionMode_DestinationIn);
p.fillRect(boundsRect, QColor(0, 0, 0, 0));

This discards the old contents and fills with transparent color.

More info at

• http://techbase.kde.org/Development/Tutorials/Graphics/Performance#QPixmap::setAlphaChannel.28.29

• http://doc.trolltech.com/qtjambi-4.4/html/com/trolltech/qt/gui/QPainter.CompositionMode.html

Edit: Better use CompositionMode_Clear and paint the rect with whatever color.