diff --git a/README b/README
index 125187e..28e6e05 100644
--- a/README
+++ b/README
@@ -15,14 +15,14 @@ GUIs in a few ways:
 
 
 To get started, install the prerequisites.  You'll need a
-Python-enabled gdb, PyGtk, and PyGktSourceView.  (And maybe more -- if
-you trip across something, let me know.)  You'll need the Python
+Python-enabled gdb, PyGObject, and PyGktSourceView.  (And maybe more
+-- if you trip across something, let me know.)  You'll need the Python
 development package to compile the small C module that is included
 here.
 
 On Fedora I think this suffices:
 
-    sudo yum install gdb python-devel pygtksourceview pygtk2
+    sudo yum install gdb python-devel gtksourceview3 pygobject3
 
 After you install this, type "make".  Now, start gdb and source the
 "SourceMe.py" file.  This sets everything up.
@@ -31,3 +31,7 @@ This adds a new "gui" command to gdb.  Currently the only subcommand
 is "gui source", which pops up a source window.  The source window
 will automatically track your progress when debugging.  You can make
 multiple source windows; they will be reused in an LRU fashion.
+
+If you want to hack on this, you will need Glade to edit the UI
+elements.  For Fedora 18, you'll need a special hack to make the
+gtksourceview widget visible to Glade.
diff --git a/gui/__init__.py b/gui/__init__.py
index e69de29..73e0db8 100644
--- a/gui/__init__.py
+++ b/gui/__init__.py
@@ -0,0 +1,18 @@
+# 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/>.
+
+import os.path
+
+self_dir = os.path.abspath(os.path.dirname(__file__))
diff --git a/gui/icons/README b/gui/icons/README
new file mode 100644
index 0000000..6ad3eaf
--- /dev/null
+++ b/gui/icons/README
@@ -0,0 +1 @@
+These icons were shamelessly taken from nemiver.
diff --git a/gui/icons/breakpoint-disabled-marker.png b/gui/icons/breakpoint-disabled-marker.png
new file mode 100644
index 0000000..569c982
Binary files /dev/null and b/gui/icons/breakpoint-disabled-marker.png differ
diff --git a/gui/icons/breakpoint-marker.png b/gui/icons/breakpoint-marker.png
new file mode 100644
index 0000000..70eb997
Binary files /dev/null and b/gui/icons/breakpoint-marker.png differ
diff --git a/gui/icons/countpoint-marker.png b/gui/icons/countpoint-marker.png
new file mode 100644
index 0000000..3700e55
Binary files /dev/null and b/gui/icons/countpoint-marker.png differ
diff --git a/gui/icons/line-pointer.png b/gui/icons/line-pointer.png
new file mode 100644
index 0000000..ca8d86d
Binary files /dev/null and b/gui/icons/line-pointer.png differ
diff --git a/gui/icons/run-to-cursor.xpm b/gui/icons/run-to-cursor.xpm
new file mode 100644
index 0000000..16607e6
--- /dev/null
+++ b/gui/icons/run-to-cursor.xpm
@@ -0,0 +1,40 @@
+/* XPM */
+static char * run_to_cursor_xpm[] = {
+"22 22 15 1",
+" 	c None",
+".	c #4A4A4A",
+"+	c #BABABA",
+"@	c #C0C0C0",
+"#	c #9C9C9C",
+"$	c #000000",
+"%	c #CCCCCC",
+"&	c #D4D4D4",
+"*	c #D7D7D8",
+"=	c #DCDCDC",
+"-	c #E3E3E3",
+";	c #EBEBEB",
+">	c #F4F3F3",
+",	c #FEFEFE",
+"'	c #B72618",
+"                      ",
+"                      ",
+"                      ",
+"    ...........       ",
+"    .++++++++@.#      ",
+"    .+++++@@@@.##     ",
+"    .++@@$$@%%....    ",
+"    .@@@%$$%&&*==.    ",
+"    .%%%%$$&*==--.    ",
+"    .%&&*$$=---;;.    ",
+"    .&*==$$;;;;>;.    ",
+"    .=-$$$$$$>>,,.    ",
+"    .;;;$$$$>,,,,.    ",
+"    .;;>>$$,,,,,,.    ",
+"    .>'''''''''',.    ",
+"    .,'''''''''',.    ",
+"    .,,,,,,,,,,,,.    ",
+"    .,,,,,,,,,,,,.    ",
+"    ..............    ",
+"                      ",
+"                      ",
+"                      "};
diff --git a/gui/icons/set-breakpoint.xpm b/gui/icons/set-breakpoint.xpm
new file mode 100644
index 0000000..f3141f9
--- /dev/null
+++ b/gui/icons/set-breakpoint.xpm
@@ -0,0 +1,52 @@
+/* XPM */
+static char * breakpoint_xpm[] = {
+"22 22 27 1",
+" 	c None",
+".	c #394248",
+"+	c #B1B5B8",
+"@	c #B6B9BC",
+"#	c #B8BBBE",
+"$	c #C0C0C0",
+"%	c #C6C9CB",
+"&	c #CBCED0",
+"*	c #D1D3D5",
+"=	c #BBBEC1",
+"-	c #BDC1C3",
+";	c #C3C7C8",
+">	c #C9CBCD",
+",	c #D4D6D8",
+"'	c #D6D8DA",
+")	c #0C1115",
+"!	c #DADCDD",
+"~	c #DEE0E1",
+"{	c #E2E3E5",
+"]	c #E6E7E8",
+"^	c #E7E8E9",
+"/	c #EBECED",
+"(	c #FF0000",
+"_	c #000000",
+":	c #F3F4F4",
+"<	c #F7F8F9",
+"[	c #FDFDFD",
+"                      ",
+"                      ",
+"                      ",
+"   ................   ",
+"   .++++++@#$$%%&*.   ",
+"   .++++@#=-;%>&,'.   ",
+"   .++))))))))))'!.   ",
+"   .+@#=-;>&*,'!~{.   ",
+"   .#=))))&,,!~{]^.   ",
+"   .-;;;,,/////^//.   ",
+"   .;(((((/)))__::.   ",
+"   .>(((((/////:<[.   ",
+"   .*(((((/))))<[[.   ",
+"   .'(((((/:<<[[[[.   ",
+"   .!(((((:_____[[.   ",
+"   .{]/:::<[[[[[[[.   ",
+"   .//))))))[[[[[[.   ",
+"   .::<<[[[[[[[[[[.   ",
+"   ................   ",
+"                      ",
+"                      ",
+"                      "};
diff --git a/gui/icons/step-into.xpm b/gui/icons/step-into.xpm
new file mode 100644
index 0000000..e168c80
--- /dev/null
+++ b/gui/icons/step-into.xpm
@@ -0,0 +1,28 @@
+/* XPM */
+static char * step_in_xpm[] = {
+"22 22 3 1",
+" 	c None",
+".	c #FF0000",
+"+	c #000000",
+"                      ",
+"                      ",
+"                      ",
+"                      ",
+"    .........         ",
+"    .........         ",
+"           ..         ",
+"        ++ .. ++      ",
+"       ++......++     ",
+"       ++ .... ++     ",
+"       ++  ..  ++     ",
+"      ++        ++    ",
+"     ++          ++   ",
+"      ++        ++    ",
+"       ++      ++     ",
+"       ++      ++     ",
+"       ++      ++     ",
+"        ++    ++      ",
+"                      ",
+"                      ",
+"                      ",
+"                      "};
diff --git a/gui/icons/step-out.xpm b/gui/icons/step-out.xpm
new file mode 100644
index 0000000..1f10cf6
--- /dev/null
+++ b/gui/icons/step-out.xpm
@@ -0,0 +1,28 @@
+/* XPM */
+static char * step_out_xpm[] = {
+"22 22 3 1",
+" 	c None",
+".	c #FF0000",
+"+	c #000000",
+"                      ",
+"                      ",
+"                .     ",
+"                ..    ",
+"          .........   ",
+"          .........   ",
+"          ..    ..    ",
+"       ++ .. ++ .     ",
+"      ++  ..  ++      ",
+"      ++  ..  ++      ",
+"      ++  ..  ++      ",
+"     ++        ++     ",
+"    ++          ++    ",
+"     ++        ++     ",
+"      ++      ++      ",
+"      ++      ++      ",
+"      ++      ++      ",
+"       ++    ++       ",
+"                      ",
+"                      ",
+"                      ",
+"                      "};
diff --git a/gui/icons/step-over.xpm b/gui/icons/step-over.xpm
new file mode 100644
index 0000000..5b68cc5
--- /dev/null
+++ b/gui/icons/step-over.xpm
@@ -0,0 +1,28 @@
+/* XPM */
+static char * step_over_xpm[] = {
+"22 22 3 1",
+" 	c None",
+".	c #FF0000",
+"+	c #000000",
+"                      ",
+"                      ",
+"                      ",
+"                .     ",
+"                ..    ",
+"   ................   ",
+"   ................   ",
+"                ..    ",
+"       ++    ++ .     ",
+"      ++      ++      ",
+"      ++      ++      ",
+"      ++      ++      ",
+"     ++        ++     ",
+"    ++          ++    ",
+"     ++        ++     ",
+"      ++      ++      ",
+"      ++      ++      ",
+"      ++      ++      ",
+"       ++    ++       ",
+"                      ",
+"                      ",
+"                      "};
diff --git a/gui/icons/throbber.gif b/gui/icons/throbber.gif
new file mode 100644
index 0000000..529e72f
Binary files /dev/null and b/gui/icons/throbber.gif differ
diff --git a/gui/invoker.py b/gui/invoker.py
new file mode 100644
index 0000000..9fa21e8
--- /dev/null
+++ b/gui/invoker.py
@@ -0,0 +1,31 @@
+# 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/>.
+
+import gdb
+
+class Invoker(object):
+    """A simple class that can invoke a gdb command.
+    This is suitable for use as an event handler in Gtk."""
+
+    def __init__(self, cmd):
+        self.cmd = cmd
+
+    # This is invoked in the gdb thread to run the command.
+    def do_call(self):
+        gdb.execute(self.cmd, from_tty = True, to_string = True)
+
+    # The object itself is the Gtk event handler.
+    def __call__(self, *args):
+        gdb.post_event(self.do_call)
diff --git a/gui/source.py b/gui/source.py
index d8bf176..9f9e7f8 100644
--- a/gui/source.py
+++ b/gui/source.py
@@ -16,9 +16,11 @@
 # Source view.
 
 import gdb
+from gui.invoker import Invoker
 import gui.startup
-import gtksourceview2 as gtksourceview
-import gtk
+import os.path
+
+from gi.repository import Gtk, GtkSource, GObject
 
 class BufferManager:
     def __init__(self):
@@ -32,7 +34,7 @@ class BufferManager:
         if filename in self.buffers:
             return self.buffers[filename]
 
-        buff = gtksourceview.Buffer()
+        buff = GtkSource.Buffer()
         buff.begin_not_undoable_action()
         try:
             contents = open(filename).read()
@@ -142,30 +144,25 @@ class SourceWindow:
     def __init__(self):
         self.frame = None
 
-        # FIXME: set the size
-        # stuff in margins
-        self.window = gtk.Window(gtk.WINDOW_TOPLEVEL)
-        self.window.set_border_width(0)
-        self.window.set_title('GDB Source')
-        self.window.set_size_request(600, 400)
+        self.do_step = Invoker("step")
+        self.do_next = Invoker("next")
+        self.do_continue = Invoker("continue")
 
-        vbox = gtk.VBox(0, False)
-        swin = gtk.ScrolledWindow()
-        self.view = gtksourceview.View()
-        self.view.set_editable(False)
-        self.view.set_cursor_visible(False)
-        self.view.set_highlight_current_line(True)
-        self.window.add(vbox)
-        vbox.pack_start(swin, True, True, 0)
-        swin.add(self.view)
+        builder = Gtk.Builder()
+        builder.add_from_file(os.path.join(gui.self_dir, 'sourcewindow.xml'))
 
-        vbox.show_all()
+        builder.connect_signals(self)
+        self.window = builder.get_object("sourcewindow")
+        self.view = builder.get_object("view")
 
-        self.window.connect("delete-event", self.deleted)
         lru_handler.add(self)
 
         self.window.show()
 
+    def do_stop(self, *args):
+        # FIXME.
+        pass
+
     def deleted(self, widget, event):
         lru_handler.remove(self)
 
@@ -180,5 +177,5 @@ class SourceWindow:
             old_buffer = self.view.get_buffer()
             self.view.set_buffer(buff)
             buffer_manager.release_buffer(old_buffer)
-            gtk.idle_add(self._do_scroll, buff, srcline - 1)
+            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/sourcewindow.xml b/gui/sourcewindow.xml
new file mode 100644
index 0000000..635e8ed
--- /dev/null
+++ b/gui/sourcewindow.xml
@@ -0,0 +1,135 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<interface>
+  <!-- interface-requires gtk+ 3.0 -->
+  <!-- interface-requires gtksourceview 3.0 -->
+  <object class="GtkImage" id="image1">
+    <property name="visible">True</property>
+    <property name="can_focus">False</property>
+    <property name="pixbuf">icons/run-to-cursor.xpm</property>
+  </object>
+  <object class="GtkImage" id="image2">
+    <property name="visible">True</property>
+    <property name="can_focus">False</property>
+    <property name="pixbuf">icons/step-over.xpm</property>
+  </object>
+  <object class="GtkImage" id="image3">
+    <property name="visible">True</property>
+    <property name="can_focus">False</property>
+    <property name="pixbuf">icons/step-into.xpm</property>
+  </object>
+  <object class="GtkWindow" id="sourcewindow">
+    <property name="can_focus">False</property>
+    <property name="title" translatable="yes">Source</property>
+    <property name="default_width">600</property>
+    <property name="default_height">400</property>
+    <signal name="delete-event" handler="deleted" swapped="no"/>
+    <child>
+      <object class="GtkBox" id="box1">
+        <property name="visible">True</property>
+        <property name="can_focus">False</property>
+        <property name="orientation">vertical</property>
+        <child>
+          <object class="GtkToolbar" id="toolbar1">
+            <property name="visible">True</property>
+            <property name="can_focus">False</property>
+            <child>
+              <object class="GtkToolButton" id="continue">
+                <property name="visible">True</property>
+                <property name="can_focus">False</property>
+                <property name="tooltip_text" translatable="yes">Continue execution</property>
+                <property name="label" translatable="yes">Continue</property>
+                <property name="use_underline">True</property>
+                <property name="icon_widget">image1</property>
+                <accelerator key="c" signal="clicked"/>
+                <signal name="clicked" handler="do_continue" swapped="no"/>
+              </object>
+              <packing>
+                <property name="expand">False</property>
+                <property name="homogeneous">True</property>
+              </packing>
+            </child>
+            <child>
+              <object class="GtkToolButton" id="next">
+                <property name="visible">True</property>
+                <property name="can_focus">False</property>
+                <property name="tooltip_text" translatable="yes">Execute one line, stepping over function calls</property>
+                <property name="label" translatable="yes">Next</property>
+                <property name="use_underline">True</property>
+                <property name="icon_widget">image2</property>
+                <accelerator key="n" signal="clicked"/>
+              </object>
+              <packing>
+                <property name="expand">False</property>
+                <property name="homogeneous">True</property>
+              </packing>
+            </child>
+            <child>
+              <object class="GtkToolButton" id="step">
+                <property name="visible">True</property>
+                <property name="can_focus">False</property>
+                <property name="tooltip_text" translatable="yes">Execute one line, stepping into function calls</property>
+                <property name="label" translatable="yes">Step</property>
+                <property name="use_underline">True</property>
+                <property name="icon_widget">image3</property>
+                <accelerator key="s" signal="clicked"/>
+                <signal name="clicked" handler="do_step" swapped="no"/>
+              </object>
+              <packing>
+                <property name="expand">False</property>
+                <property name="homogeneous">True</property>
+              </packing>
+            </child>
+            <child>
+              <object class="GtkToolButton" id="stop">
+                <property name="visible">True</property>
+                <property name="can_focus">False</property>
+                <property name="tooltip_text" translatable="yes">Interrupt the program</property>
+                <property name="label" translatable="yes">Stop</property>
+                <property name="use_underline">True</property>
+                <property name="stock_id">gtk-stop</property>
+                <accelerator key="c" signal="clicked" modifiers="GDK_CONTROL_MASK"/>
+                <signal name="clicked" handler="do_stop" swapped="no"/>
+              </object>
+              <packing>
+                <property name="expand">False</property>
+                <property name="homogeneous">True</property>
+              </packing>
+            </child>
+          </object>
+          <packing>
+            <property name="expand">False</property>
+            <property name="fill">True</property>
+            <property name="position">0</property>
+          </packing>
+        </child>
+        <child>
+          <object class="GtkScrolledWindow" id="scrolledwindow2">
+            <property name="visible">True</property>
+            <property name="can_focus">True</property>
+            <property name="shadow_type">in</property>
+            <child>
+              <object class="GtkSourceView" id="view">
+                <property name="visible">True</property>
+                <property name="can_focus">True</property>
+                <property name="has_tooltip">True</property>
+                <property name="editable">False</property>
+                <property name="left_margin">2</property>
+                <property name="right_margin">2</property>
+                <property name="cursor_visible">False</property>
+                <property name="tab_width">4</property>
+                <property name="auto_indent">True</property>
+                <property name="highlight_current_line">True</property>
+                <property name="indent_on_tab">False</property>
+              </object>
+            </child>
+          </object>
+          <packing>
+            <property name="expand">True</property>
+            <property name="fill">True</property>
+            <property name="position">1</property>
+          </packing>
+        </child>
+      </object>
+    </child>
+  </object>
+</interface>
diff --git a/gui/startup.py b/gui/startup.py
index 47b86c9..0f384d6 100644
--- a/gui/startup.py
+++ b/gui/startup.py
@@ -20,8 +20,8 @@ import Queue
 import fix_signals
 fix_signals.save()
 
-import gtk
-import glib
+from gi.repository import Gtk, Gdk, GObject, GtkSource
+
 import os
 
 (read_pipe, write_pipe) = os.pipe()
@@ -43,15 +43,17 @@ class _GtkThread(threading.Thread):
 
     def run(self):
         global read_pipe
-        glib.io_add_watch(read_pipe, glib.IO_IN, self.handle_queue)
-        gtk.main()
+        GObject.io_add_watch(read_pipe, GObject.IO_IN, self.handle_queue)
+        GObject.type_register(GtkSource.View)
+        Gtk.main()
 
 _t = None
 
 def start_gtk():
     global _t
     if _t is None:
-        gtk.gdk.threads_init()
+        GObject.threads_init()
+        Gdk.threads_init()
         _t = _GtkThread()
         _t.setDaemon(True)
         _t.start()