backporting my intro-comment of old dwm.h

dwm.c

@@ -1,4 +1,33 @@
-/* See LICENSE file for copyright and license details. */
+/* See LICENSE file for copyright and license details.
+ *
+ * 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 selects for SubstructureRedirectMask on the root window, to receive
+ * events about window (dis-)appearance.  Only one X connection at a time is
+ * allowed to select for this event mask.
+ *
+ * Calls to fetch an X event from the event queue are blocking.  Due reading
+ * 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. The event handlers of dwm are organized in an
+ * array which is accessed whenever a new event has been fetched. This allows
+ * event dispatching in O(1) time.
+ *
+ * Each child of the root window is called a client, 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.  For each client dwm
+ * creates a small title window, which is resized whenever the (_NET_)WM_NAME
+ * properties are updated or the client is moved/resized.
+ *
+ * Keys and tagging rules are organized as arrays 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 layout is
+ * represented by the lt pointer.
+ *
+ * To understand everything else, start reading main().
+ */
 #include <errno.h>
 #include <locale.h>
 #include <regex.h>