diff --git a/NOTES b/NOTES
index b1d8142..0fb28e4 100644
--- a/NOTES
+++ b/NOTES
@@ -24,6 +24,11 @@ A few notes on gdb improvements that would help the GUI:
   documented.  And, "set font" prints a line unconditionally, see bug
   14513.
 
+* Trying to add a set/show prefix is hard.  I had to add two separate
+  commands and then couldn't get "set gui" (without further args) to
+  work the way that it does in gdb.  Maybe it should just invoke
+  "help set gui"?
+
 ================================================================
 
 Windows
diff --git a/gui/display.py b/gui/display.py
index 77b9c5d..1325cca 100644
--- a/gui/display.py
+++ b/gui/display.py
@@ -32,7 +32,7 @@ class DisplayWindow(gui.updatewindow.UpdateWindow):
         self.command = command
         self.diff = diff
         self.last_text = None
-        super(DisplayWindow, self).__init__()
+        super(DisplayWindow, self).__init__('display')
 
     @in_gdb_thread
     def on_event(self):
@@ -56,7 +56,7 @@ class DisplayWindow(gui.updatewindow.UpdateWindow):
         if self.diff:
             self.tag = self.buffer.create_tag('new', foreground = 'red')
 
-        self.window.set_title('GDB "%s" @%d' % (self.command, self.number))
+        self.update_title()
         self.window.show()
 
     def _update(self, text):
diff --git a/gui/gdbutil.py b/gui/gdbutil.py
index c317a68..b6f4f4a 100644
--- a/gui/gdbutil.py
+++ b/gui/gdbutil.py
@@ -16,8 +16,25 @@
 # Little gdb utilities.
 
 import gdb
+import gdb.prompt
+
 from gui.startup import in_gdb_thread
 
+gui_prompt_substitutions = dict(gdb.prompt.prompt_substitutions)
+
+_current_window_for_prompt = None
+
+def _prompt_window(attr):
+    if _current_window_for_prompt is None:
+        return ''
+    if attr is None:
+        return ''
+    if not hasattr(_current_window_for_prompt, attr):
+        return None
+    return str(getattr(_current_window_for_prompt, attr))
+
+gui_prompt_substitutions['W'] = _prompt_window
+
 @in_gdb_thread
 def is_running():
     """Return True if the inferior is running."""
@@ -26,3 +43,31 @@ def is_running():
     if gdb.selected_thread() and gdb.selected_thread().is_running():
         return True
     return False
+
+# GDB's API should do this...
+def substitute_prompt_with_window(prompt, window):
+    global _current_window_for_prompt
+    global gui_prompt_substitutions
+    save = gdb.prompt.prompt_substitutions
+    _current_window_for_prompt = window
+    gdb.prompt.prompt_substitutions = gui_prompt_substitutions
+    try:
+        result = gdb.prompt.substitute_prompt(prompt)
+    finally:
+        gdb.prompt.prompt_substitutions = save
+        _current_window_for_prompt = None
+    return result
+
+# GDB's API should do this...
+def prompt_help_with_window(window):
+    global _current_window_for_prompt
+    global gui_prompt_substitutions
+    save = gdb.prompt.prompt_substitutions
+    _current_window_for_prompt = window
+    gdb.prompt.prompt_substitutions = gui_prompt_substitutions
+    try:
+        result = gdb.prompt.prompt_help()
+    finally:
+        gdb.prompt.prompt_substitutions = save
+        _current_window_for_prompt = None
+    return result
diff --git a/gui/logwindow.py b/gui/logwindow.py
index a46b1eb..9a74ce0 100644
--- a/gui/logwindow.py
+++ b/gui/logwindow.py
@@ -27,9 +27,13 @@ default_log_window = None
 
 class LogWindow(gui.toplevel.Toplevel):
     def __init__(self):
-        super(LogWindow, self).__init__()
+        super(LogWindow, self).__init__('log')
         global default_log_window
+        if default_log_window is not None:
+            default_log_window.default = ''
         default_log_window = self
+        # For the window title.
+        self.default = ' [Default]'
         gui.startup.send_to_gtk(self._initialize)
 
     def _initialize(self):
@@ -55,6 +59,7 @@ class LogWindow(gui.toplevel.Toplevel):
             for window in gui.toplevel.state.windows():
                 if isinstance(window, LogWindow):
                     default_log_window = window
+                    window.default = ' [Default]'
                     window.update_title()
                     break
 
@@ -68,10 +73,3 @@ class LogWindow(gui.toplevel.Toplevel):
     @in_gtk_thread
     def set_font(self, pango_font):
         self.view.modify_font(pango_font)
-
-    @in_gtk_thread
-    def update_title(self):
-        title = 'GDB Log @%d' % self.number
-        if self is default_log_window:
-            title += ' [Default]'
-        self.window.set_title(title)
diff --git a/gui/params.py b/gui/params.py
index c16e042..324b129 100644
--- a/gui/params.py
+++ b/gui/params.py
@@ -16,6 +16,7 @@
 # Parameters
 
 import gdb
+import gdb.prompt
 import gui.startup
 import gui.storage
 import gui.toplevel
@@ -30,6 +31,13 @@ class _SetBase(gdb.Command):
         super(_SetBase, self).__init__('set gui', gdb.COMMAND_NONE,
                                        prefix = True)
 
+class _SetTitleBase(gdb.Command):
+    """Generic command for modifying GUI window titles."""
+
+    def __init__(self):
+        super(_SetTitleBase, self).__init__('set gui title', gdb.COMMAND_NONE,
+                                            prefix = True)
+
 class _ShowBase(gdb.Command):
     """Generic command for showing GUI settings."""
 
@@ -37,6 +45,13 @@ class _ShowBase(gdb.Command):
         super(_ShowBase, self).__init__('show gui', gdb.COMMAND_NONE,
                                         prefix = True)
 
+class _ShowTitleBase(gdb.Command):
+    """Generic command for showing GUI window titles."""
+
+    def __init__(self):
+        super(_ShowTitleBase, self).__init__('show gui title', gdb.COMMAND_NONE,
+                                             prefix = True)
+
 class _Theme(gdb.Parameter):
     # Silly gdb requirement.
     ""
@@ -107,7 +122,45 @@ class _Font(gdb.Parameter):
         self.storage.set('font', self.value)
         return ""
 
+title_params = {}
+
+class _Title(gdb.Parameter):
+    # Silly gdb requirement.
+    ""
+
+    def __init__(self, name, default):
+        title_params[name] = self
+        self.name = name
+        self.set_doc = "Set the %s window title format." % self.name
+        self.show_doc = "Show the %s window title format." % self.name
+        self.manager = GtkSource.StyleSchemeManager.get_default()
+        self.storage = gui.storage.storage_manager
+        super(_Title, self).__init__('gui title %s' % name, gdb.COMMAND_NONE,
+                                     gdb.PARAM_STRING)
+        val = self.storage.get('title-%s' % name)
+        if val is not None:
+            self.value = val
+        else:
+            self.value = default
+
+    @in_gdb_thread
+    def get_show_string(self, pvalue):
+        return "The current title format for the %s is: %s" % (self.name,
+                                                               self.value)
+
+    @in_gdb_thread
+    def get_set_string(self):
+        # gui.toplevel.state.set_font(self.value)
+        self.storage.set('title-%s' % self.name, self.value)
+        return ""
+
 _SetBase()
+_SetTitleBase()
 _ShowBase()
+_ShowTitleBase()
 source_theme = _Theme()
 font_manager = _Font()
+
+_Title('source', '\\W{basename} [GDB Source @\\W{number}]')
+_Title('display', '\\W{command} [GDB Display @\\W{number}]')
+_Title('log', '[GDB Log @\\W{number}]\\W{default}')
diff --git a/gui/source.py b/gui/source.py
index d84285c..26c49d7 100644
--- a/gui/source.py
+++ b/gui/source.py
@@ -19,7 +19,6 @@ import gdb
 import gui
 import gui.updatewindow
 from gui.invoker import Invoker
-from gui.toplevel import Toplevel
 import gui.startup
 from gui.startup import in_gdb_thread, in_gtk_thread
 import gui.toplevel
@@ -197,7 +196,7 @@ class SourceWindow(gui.updatewindow.UpdateWindow):
         return GdkPixbuf.Pixbuf.new_from_file(path)
 
     def __init__(self):
-        super(SourceWindow, self).__init__()
+        super(SourceWindow, self).__init__('source')
         gdb.events.cont.connect(self._on_cont_event)
 
     @in_gtk_thread
@@ -233,7 +232,7 @@ class SourceWindow(gui.updatewindow.UpdateWindow):
 
         lru_handler.add(self)
 
-        self.window.set_title('GDB Source @%d' % self.number)
+        self.update_title()
         self.window.show()
 
     @in_gtk_thread
@@ -281,9 +280,9 @@ class SourceWindow(gui.updatewindow.UpdateWindow):
         if buff is not None:
             old_buffer = self.view.get_buffer()
             self.view.set_buffer(buff)
-            # Might be good to let the user pick the format...
-            self.window.set_title('%s - GDB Source @%d'
-                                  % (os.path.basename(srcfile), self.number))
+            self.fullname = srcfile
+            self.basename = os.path.basename(srcfile)
+            self.update_title()
             buffer_manager.release_buffer(old_buffer)
             GObject.idle_add(self._do_scroll, buff, srcline - 1)
             # self.view.scroll_to_iter(buff.get_iter_at_line(srcline), 0.0)
diff --git a/gui/toplevel.py b/gui/toplevel.py
index 7e0333e..fb499e0 100644
--- a/gui/toplevel.py
+++ b/gui/toplevel.py
@@ -16,8 +16,11 @@
 # Toplevel handling.
 
 import gdb
+import gui.gdbutil
+import gui.params
 import gui.startup
 import threading
+
 from gi.repository import Pango
 from gui.startup import in_gdb_thread, in_gtk_thread
 
@@ -77,10 +80,11 @@ class _ToplevelState(object):
 state = _ToplevelState()
 
 class Toplevel(object):
-    def __init__(self):
+    def __init__(self, window_type):
         state.add(self)
         # The subclass must set this.
         self.window = None
+        self.window_type = window_type
 
     def destroy(self):
         state.remove(self)
@@ -95,3 +99,9 @@ class Toplevel(object):
         # Subclasses can override this to be notified when the user
         # changes the font.
         pass
+
+    @in_gtk_thread
+    def update_title(self):
+        fmt = gui.params.title_params[self.window_type].value
+        title = gui.gdbutil.substitute_prompt_with_window(fmt, self)
+        self.window.set_title(title)
diff --git a/gui/updatewindow.py b/gui/updatewindow.py
index f58f939..31b9af9 100644
--- a/gui/updatewindow.py
+++ b/gui/updatewindow.py
@@ -27,8 +27,8 @@ class UpdateWindow(Toplevel):
     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__()
+    def __init__(self, window_type):
+        super(UpdateWindow, self).__init__(window_type)
         gui.startup.send_to_gtk(self.gtk_initialize)
         self._connect_events()
         # Display the data now.