window must be kept above other windows. If the
window was already above, then this function does nothing.
- a toplevel
- whether to keep
windowabove other windows
On X11, asks the window manager to keep
window above, if the window
manager supports this operation. Not all window managers support
this, and some deliberately ignore it or don't have a concept of
"keep above"; so you can't rely on the window being kept above.
But it will happen with most standard window managers,
and GDK makes a best effort to get it to happen.