diff --git a/rfb/UpdateTracker.cxx b/rfb/UpdateTracker.cxx
new file mode 100644
index 0000000..cc0fb10
--- /dev/null
+++ b/rfb/UpdateTracker.cxx
@@ -0,0 +1,172 @@
+/* Copyright (C) 2002-2004 RealVNC Ltd.  All Rights Reserved.
+ *    
+ * This 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 software 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 software; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307,
+ * USA.
+ */
+
+// -=- rfbUpdateTracker.cpp
+//
+// Tracks updated regions and a region-copy event, too
+//
+
+#include <assert.h>
+
+#include <rfb/UpdateTracker.h>
+#include <rfb/LogWriter.h>
+
+using namespace rfb;
+
+static LogWriter vlog("UpdateTracker");
+
+// -=- ClippedUpdateTracker
+
+void ClippedUpdateTracker::add_changed(const Region &region) {
+  child.add_changed(region.intersect(cliprgn));
+}
+
+void ClippedUpdateTracker::add_copied(const Region &dest, const Point &delta) {
+  // Clip the destination to the display area
+  Region clipdest = dest.intersect(cliprgn);
+  if (clipdest.is_empty())  return;
+
+  // Clip the source to the screen
+  Region tmp = clipdest;
+  tmp.translate(delta.negate());
+  tmp.assign_intersect(cliprgn);
+  if (!tmp.is_empty()) {
+    // Translate the source back to a destination region
+    tmp.translate(delta);
+
+    // Pass the copy region to the child tracker
+    child.add_copied(tmp, delta);
+  }
+
+  // And add any bits that we had to remove to the changed region
+  tmp = clipdest.subtract(tmp);
+  if (!tmp.is_empty()) {
+    child.add_changed(tmp);
+  }
+}
+
+// SimpleUpdateTracker
+
+SimpleUpdateTracker::SimpleUpdateTracker(bool use_copyrect) {
+  copy_enabled = use_copyrect;
+}
+
+SimpleUpdateTracker::~SimpleUpdateTracker() {
+}
+
+void SimpleUpdateTracker::enable_copyrect(bool enable) {
+  if (!enable && copy_enabled) {
+    add_changed(copied);
+    copied.clear();
+  }
+  copy_enabled=enable;
+}
+
+void SimpleUpdateTracker::add_changed(const Region &region) {
+  changed.assign_union(region);
+}
+
+void SimpleUpdateTracker::add_copied(const Region &dest, const Point &delta) {
+  // Do we support copyrect?
+  if (!copy_enabled) {
+    add_changed(dest);
+    return;
+  }
+
+  // Is there anything to do?
+  if (dest.is_empty()) return;
+
+  // Calculate whether any of this copy can be treated as a continuation
+  // of an earlier one
+  Region src = dest;
+  src.translate(delta.negate());
+  Region overlap = src.intersect(copied);
+
+  if (overlap.is_empty()) {
+    // There is no overlap
+
+    Rect newbr = dest.get_bounding_rect();
+    Rect oldbr = copied.get_bounding_rect();
+    if (oldbr.area() > newbr.area()) {
+      // Old copyrect is (probably) bigger - use it
+      changed.assign_union(dest);
+    } else {
+      // New copyrect is probably bigger
+      // Use the new one
+      // But be careful not to copy stuff that still needs
+      // to be updated.
+      Region invalid_src = src.intersect(changed);
+      invalid_src.translate(delta);
+      changed.assign_union(invalid_src);
+      changed.assign_union(copied);
+      copied = dest;
+      copy_delta = delta;
+    }
+    return;
+  }
+
+  Region invalid_src = overlap.intersect(changed);
+  invalid_src.translate(delta);
+  changed.assign_union(invalid_src);
+  
+  overlap.translate(delta);
+
+  Region nonoverlapped_copied = dest.union_(copied).subtract(overlap);
+  changed.assign_union(nonoverlapped_copied);
+
+  copied = overlap;
+  copy_delta = copy_delta.translate(delta);
+
+  return;
+}
+
+void SimpleUpdateTracker::subtract(const Region& region) {
+  copied.assign_subtract(region);
+  changed.assign_subtract(region);
+}
+
+void SimpleUpdateTracker::get_update(UpdateInfo* info, const Region& clip)
+{
+  copied.assign_subtract(changed);
+  info->changed = changed.intersect(clip);
+  info->copied = copied.intersect(clip);
+  info->copy_delta = copy_delta;
+}
+
+void SimpleUpdateTracker::flush_update(UpdateTracker &info,
+                                       const Region &cliprgn)
+{
+  Region copied_clipped = copied.intersect(cliprgn);
+  Region changed_clipped = changed.intersect(cliprgn);
+  copied.assign_subtract(copied_clipped);
+  changed.assign_subtract(changed_clipped);
+  if (!copied_clipped.is_empty()) {
+    info.add_copied(copied_clipped, copy_delta);
+  }
+  if (!changed_clipped.is_empty())
+    info.add_changed(changed_clipped);
+}
+
+void SimpleUpdateTracker::get_update(UpdateTracker &to) const {
+  if (!copied.is_empty()) {
+    to.add_copied(copied, copy_delta);
+  }
+  if (!changed.is_empty()) {
+    to.add_changed(changed);
+  }
+}