*

 * dynamic window manager is designed like any other X client as well. It is

 * driven through handling X events. In contrast to other X clients, a window

 * manager like dwm selects for SubstructureRedirectMask on the root window, to

 * receive events about child window appearance and disappearance.  Only one X

 * connection at a time is allowed to select for this event mask by any X

 * server, thus only one window manager instance can be executed at a time.

 * Any attempt to select for SubstructureRedirectMask by any connection after

 * another connection already selected for those events, will result in an

 * error generated by the server. Such errors are reported through calling the

 * current X error handler.

 *

 * Calls to pop an X event from the event queue of the X connection are

 * blocking.  Due the fact, that dwm reads status text from standard input, a

 * select-driven main loop has been implemented which selects for reads on the

 * X connection and STDIN_FILENO to handle all data smoothly and without

 * busy-loop quirks..  The event handlers of dwm are organized in an array

 * which is accessed whenever a new event has been popped. This allows event

 * dispatching in O(1) time.

 *

 * Each child window of the root window is called a client in window manager

 * terminology, except windows which have set the override_redirect flag.

 * Clients are organized in a global doubly-linked client list, the focus

 * history is remembered through a global stack list. Each client contains an

 * array of Bools of the same size as the global tags array to indicate the

 * tags of a client. There are no other data structures to organize the clients

 * in tag lists, because a single global list is most simple. All clients which

 * have at least one tag enabled of the current tags viewed, will be visible on

 * the screen, all other clients are banned to the x-location 2 * screen width.

 * This avoids having additional layers of workspace handling.

 *

 * For each client dwm creates a small title window which is resized whenever

 * the WM_NAME or _NET_WM_NAME properties are updated.

 *

 * Keys and tagging rules are organized as arrays as well and defined in the

 * config.h file. These arrays are kept static in event.o and tag.o

 * respectively, because no other part of dwm needs access to them.

 *

 * The current mode is represented by the arrange function pointer which wether

 * points to dofloat or dotile.