First draft of guisupport added to lib.

Projects should use this code to get GUI application objects and
start event loops.

IPython/lib/guisupport.py

@@ -0,0 +1,140 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.
+
+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:
+        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()
+    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()
+    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
+#-----------------------------------------------------------------------------