transparent background

[wysota]

Define "doesn't work". The mask is certainly invalid...

[fruzzo]

Define "doesn't work". The mask is certainly invalid...

"doesn't work" = the widget is filled with black color and don't draw anithing.

[wysota]

I suggest you take a look at some working paintEvent() implementation, because yours doesn't make any sense. Look how you created the painter object - you didn't tell it what to paint on.