Add better tracking of real stacking order

Wedging override-redirect windows into the constraint code in stack.c
results in Mutter getting confused about the stacking order of
these windows with respect to other windows, and may also in some
cases cause Mutter to restack override-redirect windows.

core/stack-tracker.c core/stack-tracker.h: MetaStackTracker - combine
  events received from the X server with local changes we have made
  to come up with the best possible idea of what the stacking order
  is at any one point in time.

core/screen.c core/screen-private.h: Create a MetaStackTracker for
  the screen.

core/display.c: Feed relevant events to MetaStackTracker

core/frame.c core/screen.c core/stack.c: When we make changes to the
  stacking order or add windows, record those changes immediatley
  in MetaStackTracker so we have the information without waiting
  for a round-trip.

include/ui.h ui/ui.c: meta_ui_create_frame_window add a return value
  for the X request serial used to create the window.

http://bugzilla.gnome.org/show_bug.cgi?id=585984

src/core/stack-tracker.h

@@ -0,0 +1,86 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
+
+/**
+ * \file stack-tracker.h  Track stacking order for compositor
+ *
+ * MetaStackTracker maintains the most accurate view we have at a
+ * given point of time of the ordering of the children of the root
+ * window (including override-redirect windows.) This is used to order
+ * the windows when the compositor draws them.
+ *
+ * By contrast, MetaStack is responsible for keeping track of how we
+ * think that windows *should* be ordered.  For windows we manage
+ * (non-override-redirect windows), the two stacking orders will be
+ * the same.
+ */
+
+/*
+ * Copyright (C) 2009 Red Hat, Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
+ */
+
+#ifndef META_STACK_TRACKER_H
+#define META_STACK_TRACKER_H
+
+#include "screen.h"
+
+typedef struct _MetaStackTracker MetaStackTracker;
+
+MetaStackTracker *meta_stack_tracker_new  (MetaScreen       *screen);
+void              meta_stack_tracker_free (MetaStackTracker *tracker);
+
+/* These functions are called when we make an X call that changes the
+ * stacking order; this allows MetaStackTracker to predict stacking
+ * order before it receives events back from the X server */
+void meta_stack_tracker_record_add             (MetaStackTracker *tracker,
+						Window            window,
+                                                gulong            serial);
+void meta_stack_tracker_record_remove          (MetaStackTracker *tracker,
+						Window            window,
+                                                gulong            serial);
+void meta_stack_tracker_record_restack_windows (MetaStackTracker *tracker,
+						Window           *windows,
+						int               n_windows,
+                                                gulong            serial);
+void meta_stack_tracker_record_raise_above     (MetaStackTracker *tracker,
+						Window            window,
+						Window            sibling,
+                                                gulong            serial);
+void meta_stack_tracker_record_lower_below    (MetaStackTracker *tracker,
+						Window            window,
+						Window            sibling,
+                                                gulong            serial);
+void meta_stack_tracker_record_lower           (MetaStackTracker *tracker,
+						Window            window,
+                                                gulong            serial);
+
+/* These functions are used to update the stack when we get events
+ * reflecting changes to the stacking order */
+void meta_stack_tracker_create_event    (MetaStackTracker    *tracker,
+					 XCreateWindowEvent  *event);
+void meta_stack_tracker_destroy_event   (MetaStackTracker    *tracker,
+					 XDestroyWindowEvent *event);
+void meta_stack_tracker_reparent_event  (MetaStackTracker    *tracker,
+					 XReparentEvent      *event);
+void meta_stack_tracker_configure_event (MetaStackTracker    *tracker,
+					 XConfigureEvent     *event);
+
+void meta_stack_tracker_get_stack (MetaStackTracker *tracker,
+				   Window          **windows,
+				   int              *n_windows);
+
+#endif /* META_STACK_TRACKER_H */