setBackgroundRole( QPalette::NoRole );//NoBackground );
// set focus policy to threat QContextMenuEvent from keyboard
setFocusPolicy( Qt::StrongFocus );
-#if (QT_VERSION < QT_VERSION_CHECK(5, 0, 0) && OCC_VERSION_LARGE < 0x07000000) || QT_VERSION >= QT_VERSION_CHECK(5, 6, 0)
setAttribute( Qt::WA_PaintOnScreen );
-#endif
setAttribute( Qt::WA_NoSystemBackground );
}