diff --git a/gui/display.py b/gui/display.py
index c2eea35..d1e71e2 100644
--- a/gui/display.py
+++ b/gui/display.py
@@ -16,7 +16,7 @@
 # Log window.
 
 import gdb
-import gui.toplevel
+import gui.updatewindow
 import gui.startup
 from gi.repository import Gtk
 import functools
@@ -26,30 +26,13 @@ import gui.events
 # FIXME: TO DO:
 # * highlight the changes
 
-class DisplayWindow(gui.toplevel.Toplevel):
+class DisplayWindow(gui.updatewindow.UpdateWindow):
     def __init__(self, command):
-        super(DisplayWindow, self).__init__()
         self.command = command
-        gui.startup.send_to_gtk(self._initialize)
-        self._connect_events()
-        # Display the data now.
-        self._on_event()
+        super(DisplayWindow, self).__init__()
 
     @in_gdb_thread
-    def _connect_events(self):
-        # FIXME - we need an event for "selected frame changed".
-        # ... and thread-changed
-        # really just pre-prompt would be good enough
-        gdb.events.stop.connect(self._on_event)
-        gui.events.frame_changed.connect(self._on_event)
-
-    @in_gdb_thread
-    def _disconnect_events(self):
-        gdb.events.stop.disconnect(self.on_event)
-        gui.event.frame_changed.disconnect(self.on_event)
-
-    @in_gdb_thread
-    def _on_event(self, *args):
+    def on_event(self):
         try:
             text = gdb.execute(self.command, to_string = True)
         except gdb.error as what:
@@ -57,7 +40,7 @@ class DisplayWindow(gui.toplevel.Toplevel):
         gui.startup.send_to_gtk(lambda: self._update(text))
 
     @in_gtk_thread
-    def _initialize(self):
+    def gtk_initialize(self):
         builder = gui.startup.create_builder('logwindow.xml')
         builder.connect_signals(self)
 
@@ -68,12 +51,6 @@ class DisplayWindow(gui.toplevel.Toplevel):
         self.window.set_title('GDB "%s" @%d' % (self.command, self.number))
         self.window.show()
 
-    @in_gtk_thread
-    def remove(self, window):
-        self.windows.remove(window)
-        if len(self.windows) == 0:
-            gdb.post_event(self._disconnect_events)
-
     def _update(self, text):
         self.buffer.delete(self.buffer.get_start_iter(),
                            self.buffer.get_end_iter())
diff --git a/gui/updatewindow.py b/gui/updatewindow.py
new file mode 100644
index 0000000..7c0da2d
--- /dev/null
+++ b/gui/updatewindow.py
@@ -0,0 +1,74 @@
+# Copyright (C) 2013 Tom Tromey <tom@tromey.com>
+
+# 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 3 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, see <http://www.gnu.org/licenses/>.
+
+# Auto-updating window.
+
+from gui.toplevel import Toplevel
+import gui.startup
+from gui.startup import in_gdb_thread, in_gtk_thread
+import gdb
+import gui.events
+
+class UpdateWindow(Toplevel):
+    """A window that automatically updates in response to gdb changes.
+
+    In particular, starting or stopping the inferior, or switching
+    frames, causes this window to be eligible for updates."""
+
+    def __init__(self):
+        super(UpdateWindow, self).__init__()
+        gui.startup.send_to_gtk(self.gtk_initialize)
+        self._connect_events()
+        # Display the data now.
+        self.on_event()
+
+    @in_gtk_thread
+    def gtk_initialize(self):
+        """Subclasses should implement this method to do initialization
+        in the Gtk thread."""
+        pass
+
+    # FIXME: really ought to be passing in an event here.
+    @in_gdb_thread
+    def on_event(self):
+        """Subclasses should implement this method.
+        It is called with no arguments when the state changes."""
+        pass
+
+    @in_gdb_thread
+    def _connect_events(self):
+        # FIXME - we need an event for "selected frame changed".
+        # ... and thread-changed
+        # really just pre-prompt would be good enough
+        gdb.events.stop.connect(self._on_event)
+        gui.events.frame_changed.connect(self._on_event)
+
+    @in_gdb_thread
+    def _disconnect_events(self):
+        gdb.events.stop.disconnect(self._on_event)
+        gui.event.frame_changed.disconnect(self._on_event)
+
+    @in_gdb_thread
+    def _on_event(self, *args):
+        try:
+            text = gdb.execute(self.command, to_string = True)
+        except gdb.error as what:
+            text = str(what)
+        gui.startup.send_to_gtk(lambda: self._update(text))
+
+    @in_gtk_thread
+    def deleted(self):
+        gdb.post_event(self._disconnect_events)
+        self.destroy()