diff --git a/x0vncserver/PollingManager.cxx b/x0vncserver/PollingManager.cxx
new file mode 100644
index 0000000..50c116e
--- /dev/null
+++ b/x0vncserver/PollingManager.cxx
@@ -0,0 +1,127 @@
+/* Copyright (C) 2004-2005 Constantin Kaplinsky.  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.
+ */
+//
+// PollingManager.cxx
+//
+
+#include <stdio.h>
+#include <string.h>
+#include <sys/time.h>
+#include <X11/Xlib.h>
+#include <rfb/VNCServer.h>
+
+#include <x0vncserver/Image.h>
+#include <x0vncserver/PollingManager.h>
+
+const int PollingManager::m_pollingOrder[32] = {
+   0, 16,  8, 24,  4, 20, 12, 28,
+  10, 26, 18,  2, 22,  6, 30, 14,
+   1, 17,  9, 25,  7, 23, 15, 31,
+  19,  3, 27, 11, 29, 13,  5, 21
+};
+
+//
+// Constructor. Note that dpy and image should remain valid during
+// object lifetime, while factory is used only in the constructor
+// itself.
+//
+
+PollingManager::PollingManager(Display *dpy, Image *image,
+                               ImageFactory *factory)
+  : m_dpy(dpy), m_server(0), m_image(image), m_pollingStep(0)
+{
+  // Create two additional images used in the polling algorithm.
+  // FIXME: verify that these images use the same pixel format as in m_image.
+  m_rowImage = factory->newImage(m_dpy, m_image->xim->width, 1);
+  m_tileImage = factory->newImage(m_dpy, 32, 32);
+}
+
+void PollingManager::setVNCServer(VNCServer* s)
+{
+  m_server = s;
+}
+
+//
+// DEBUG: a version of poll() measuring time spent in the function.
+//
+
+void PollingManager::pollDebug()
+{
+  struct timeval timeSaved, timeNow;
+  struct timezone tz;
+  timeSaved.tv_sec = 0;
+  timeSaved.tv_usec = 0;
+  gettimeofday(&timeSaved, &tz);
+
+  poll();
+
+  gettimeofday(&timeNow, &tz);
+  int diff = (int)((timeNow.tv_usec - timeSaved.tv_usec + 500) / 1000 +
+                   (timeNow.tv_sec - timeSaved.tv_sec) * 1000);
+  if (diff != 0)
+    fprintf(stderr, "DEBUG: poll(): %4d ms\n", diff);
+}
+
+//
+// Search for changed rectangles on the screen.
+//
+
+void PollingManager::poll()
+{
+  if (!m_server)
+    return;
+
+  int nTilesChanged = 0;
+  int scanLine = m_pollingOrder[m_pollingStep++ % 32];
+  int bytesPerPixel = m_image->xim->bits_per_pixel / 8;
+  int bytesPerLine = m_image->xim->bytes_per_line;
+  int w = m_image->xim->width, h = m_image->xim->height;
+  Rect rect;
+
+  for (int y = 0; y * 32 < h; y++) {
+    int tile_h = (h - y * 32 >= 32) ? 32 : h - y * 32;
+    if (scanLine >= tile_h)
+      continue;
+    int scan_y = y * 32 + scanLine;
+    m_rowImage->get(DefaultRootWindow(m_dpy), 0, scan_y);
+    char *ptr_old = m_image->xim->data + scan_y * bytesPerLine;
+    char *ptr_new = m_rowImage->xim->data;
+    for (int x = 0; x * 32 < w; x++) {
+      int tile_w = (w - x * 32 >= 32) ? 32 : w - x * 32;
+      int nBytes = tile_w * bytesPerPixel;
+      if (memcmp(ptr_old, ptr_new, nBytes)) {
+        if (tile_w == 32 && tile_h == 32) {
+          m_tileImage->get(DefaultRootWindow(m_dpy), x * 32, y * 32);
+        } else {
+          m_tileImage->get(DefaultRootWindow(m_dpy), x * 32, y * 32,
+                           tile_w, tile_h);
+        }
+        m_image->updateRect(m_tileImage, x * 32, y * 32);
+        rect.setXYWH(x * 32, y * 32, tile_w, tile_h);
+        m_server->add_changed(rect);
+        nTilesChanged++;
+      }
+      ptr_old += nBytes;
+      ptr_new += nBytes;
+    }
+  }
+
+  if (nTilesChanged)
+    m_server->tryUpdate();
+}
+