enum WindowFrame

Who draws a window's non-client area.

The compositor's title bar is a service, not a law: it exists so that every client gets a drag handle and a close button without writing one, and so that a client which has stopped answering can still be closed. An app that does write its own gets nothing from it but a 32-pixel strip of somebody else's design above its own, which is exactly the space a toolbar it is already drawing would have used.

So it is the client's choice, made once, at CreateSurface — not a call that turns the strip off later, which would mean opening a window with a frame and taking it away a frame afterwards.

What the compositor keeps either way is everything that cannot be trusted to the client: where the window is, whether it is maximized, which workspace it is on, and the pointer that resizes it. A client window asks for those through BeginMove, ToggleMaximize and Minimize rather than doing them itself, and a client that never asks is a client with a window the user can still move.

Wayland windows are not offered this. Their frame is negotiated through xdg-decoration, which is a protocol this one has no business duplicating.