http://tronche.com/gui/x/icccm/sec-4.html#s-4.2.2

↑の 4.2.9. Redirecting Requests に今の議題に非常に関係したことが
書かれているらしい。

SubstructureRedirect : サイズ変更時に親に通知されるイベント
ResizeRedirect : サイズ変更時に自分に通知されるイベント
ResizeRequest : Window Manager が送ってくるイベント


In particular, clients that need to take some special action if they
are resized can select for ResizeRedirect events on their top-level
windows. They will receive a ResizeRequest event if the window manager
resizes their window, and the resize will not actually take place.
Clients are free to make what use they like of the information that
the window manager wants to change their size, but they must configure
the window to the width and height specified in the event in a timely
fashion. To ensure that the resize will actually happen at this stage
instead of being intercepted and executed by the window manager
(and thus restarting the process), the client needs temporarily to set
override-redirect on the window.