+// In addition to the basic key/button press/release events, by registering for
+// events like SubstructureRedirect, we are declaring our intent to act as
+// window manager for this X server. Only one WM is allowed per X server, a
+// policy enforced on the X server's side by refusing the registration request
+// for events like SubstructureRedirect if an existing process already receives
+// those events (i.e. is already the window manager).