Works well in Ubuntu 10.04

All buttons visible and all buttons enabled: setWindowFlags(Qt::Tool)
All buttons visible, close and maximize buttons enabled, minimize button disabled: setWindowFlags(Qt::Tool | Qt::WindowTitleHint | Qt::WindowMaximizeButtonHint | Qt::WindowCloseButtonHint | Qt::CustomizeWindowHint)
All buttons visible, maximize button enabled, close and minimize disabled: setWindowFlags(Qt::Tool | Qt::WindowTitleHint | Qt::WindowMaximizeButtonHint | Qt::CustomizeWindowHint)
Only close button is visible and enabled setWindowFlags(Qt::Tool | Qt::WindowTitleHint | Qt::WindowCloseButtonHint | Qt::CustomizeWindowHint)
No buttons in title bar: setWindowFlags(Qt::Tool | Qt::WindowTitleHint | Qt::WindowCloseButtonHint | Qt::CustomizeWindowHint)