Fixing bug in guisupport.py

IPython/lib/guisupport.py

@@ -1,143 +1,145 b''
 #!/usr/bin/env python
 # coding: utf-8
 """
 Support for creating GUI apps and starting event loops.
 
 IPython's GUI integration allows interative plotting and GUI usage in IPython
 session. IPython has two different types of GUI integration:
 
 1. The terminal based IPython supports GUI event loops through Python's
    PyOS_InputHook. PyOS_InputHook is a hook that Python calls periodically
    whenever raw_input is waiting for a user to type code. We implement GUI
    support in the terminal by setting PyOS_InputHook to a function that 
    iterates the event loop for a short while. It is important to note that
    in this situation, the real GUI event loop is NOT run in the normal
    manner, so you can't use the normal means to detect that it is running.
 2. In the two process IPython kernel/frontend, the GUI event loop is run in 
    the kernel. In this case, the event loop is run in the normal manner by
    calling the function or method of the GUI toolkit that starts the event
    loop.
 
 In addition to starting the GUI event loops in one of these two ways, IPython
 will *always* create an appropriate GUI application object when GUi
 integration is enabled.
 
 If you want your GUI apps to run in IPython you need to do two things:
 
 1. Test to see if there is already an existing main application object. If
    there is, you should use it. If there is not an existing application object
    you should create one.
 2. Test to see if the GUI event loop is running. If it is, you should not
    start it. If the event loop is not running you may start it.
 
 This module contains functions for each toolkit that perform these things
 in a consistent manner. Because of how PyOS_InputHook runs the event loop
 you cannot detect if the event loop is running using the traditional calls
 (such as ``wx.GetApp.IsMainLoopRunning()`` in wxPython). If PyOS_InputHook is
 set These methods will return a false negative. That is, they will say the
 event loop is not running, when is actually is. To work around this limitation
 we proposed the following informal protocol:
 
 * Whenever someone starts the event loop, they *must* set the ``_in_event_loop``
   attribute of the main application object to ``True``. This should be done
   regardless of how the event loop is actually run.
 * Whenever someone stops the event loop, they *must* set the ``_in_event_loop``
   attribute of the main application object to ``False``.
 * If you want to see if the event loop is running, you *must* use ``hasattr``
   to see if ``_in_event_loop`` attribute has been set. If it is set, you
   *must* use its value. If it has not been set, you can query the toolkit
   in the normal manner.
 * If you want GUI support and no one else has created an application or
   started the event loop you *must* do this. We don't want projects to 
   attempt to defer these things to someone else if they themselves need it.
 
 The functions below implement this logic for each GUI toolkit. If you need
 to create custom application subclasses, you will likely have to modify this
 code for your own purposes. This code can be copied into your own project
 so you don't have to depend on IPython.
 
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2008-2010  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # wx
 #-----------------------------------------------------------------------------
 
 def get_app_wx(*args, **kwargs):
     """Create a new wx app or return an exiting one."""
     import wx
     app = wx.GetApp()
     if app is None:
         app = wx.PySimpleApp(*args, **kwargs)
     return app
 
 def is_event_loop_running_wx(app=None):
     """Is the wx event loop running."""
     if app is None:
         app = get_app_wx()
     if hasattr(app, '_in_event_loop'):
         return app._in_event_loop
     else:
         return app.IsMainLoopRunning()
 
 def start_event_loop_wx(app=None):
     """Start the wx event loop in a consistent manner."""
     if app is None:
         app = get_app_wx()
     if not is_event_loop_running_wx(app):
         app._in_event_loop = True
         app.MainLoop()
         app._in_event_loop = False
     else:
         app._in_event_loop = True
 
 #-----------------------------------------------------------------------------
 # qt4
 #-----------------------------------------------------------------------------
 
 def get_app_qt4(*args, **kwargs):
     """Create a new qt4 app or return an existing one."""
     from PyQt4 import QtGui
     app = QtGui.QApplication.instance()
     if app is None:
+        if not args:
+            args = ([''],)
         app = QtGui.QApplication(*args, **kwargs)
     return app
 
 def is_event_loop_running_qt4(app=None):
     """Is the qt4 event loop running."""
     if app is None:
-        app = get_app_qt4()
+        app = get_app_qt4([''])
     if hasattr(app, '_in_event_loop'):
         return app._in_event_loop
     else:
         # Does qt4 provide a other way to detect this?
         return False
 
 def start_event_loop_qt4(app=None):
     """Start the qt4 event loop in a consistent manner."""
     if app is None:
-        app = get_app_qt4()
+        app = get_app_qt4([''])
     if not is_event_loop_running_qt4(app):
         app._in_event_loop = True
         app.exec_()
         app._in_event_loop = False
     else:
         app._in_event_loop = True
 
 #-----------------------------------------------------------------------------
 # Tk
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # gtk
 #-----------------------------------------------------------------------------