Index: twisted/internet/gtk2reactor.py
===================================================================
--- twisted/internet/gtk2reactor.py	(revision 14339)
+++ twisted/internet/gtk2reactor.py	(working copy)
@@ -30,8 +30,9 @@
 try:
     if not hasattr(sys, 'frozen'):
         # Don't want to check this for py2exe
-        import pygtk
-        pygtk.require('2.0')
+       	import pygtk
+       	if not sys.modules.has_key('gtk'):
+       		pygtk.require('2.0')
 except (ImportError, AttributeError):
     pass # maybe we're using pygtk before this hack existed.
 import gobject
@@ -79,7 +80,7 @@
 
     implements(IReactorFDSet)
 
-    def __init__(self, useGtk=True):
+    def __init__(self, useGtk=True, useExistingGtk=False):
         self.context = gobject.main_context_default()
         self.loop = gobject.MainLoop()
         posixbase.PosixReactorBase.__init__(self)
@@ -96,7 +97,10 @@
             self.__pending = gtk.events_pending
             self.__iteration = gtk.main_iteration
             self.__crash = _our_mainquit
-            self.__run = gtk.main
+            if useExistingGtk:
+            	self.__run = lambda: None
+            else:
+            	self.__run = gtk.main
 
     # The input_add function in pygtk1 checks for objects with a
     # 'fileno' method and, if present, uses the result of that method
@@ -253,13 +257,15 @@
         _simtag = gobject.timeout_add(int(timeout * 1010), self.simulate)
 
 
-def install(useGtk=True):
+def install(useGtk=True, useExistingGtk=False):
     """Configure the twisted mainloop to be run inside the gtk mainloop.
 
     @param useGtk: should glib rather than GTK+ event loop be
     used (this will be slightly faster but does not support GUI).
+    @param useExistingGtk: When used in combination with useGtk,
+    do not launch gtk.main, but use the existing gtk mainloop.
     """
-    reactor = Gtk2Reactor(useGtk)
+    reactor = Gtk2Reactor(useGtk, useExistingGtk)
     from twisted.internet.main import installReactor
     installReactor(reactor)
     return reactor