Specifies whether the panel appears on top of all windows, or just on top of the window the panel is in. If this attribute is not set, the popup window level depends on the platform. On Linux, the default value is top, otherwise, the default value is parent. If a panel has one or more text fields, this attribute should not be set, otherwise IME or on-screen keyboard popups will appear incorrectly. For these reasons, you should avoid setting the level if not needed.
The panel is shown in front of all other normal windows, including those of other applications.
The panel is shown just above the window the panel is in, but behind other windows above it. If anchored, the child window maintains its relative position to its parent window.
The panel floats above the window the panel is in. On Mac, the panel is only visible when the application is active.