inputhook: disable CTRL+C when a hook is active.

On systems with 'readline', it's very likely to intercept a signal
during a select() call. The default SIGINT handler will schedule a
KeyboardInterrupt exception to be raised as soon as possible. If
ctypes is used to install a Python callback for PyOS_InputHook, this
will happen as soon as the bytecode execution starts, so even if the
first instruction of the callback is a
`try: ... except KeyboardInterrupt` clause, it's actually too late.

As ctypes doesn't allow a Python callback to raise an exception, this
ends up with IPython detecting an internal error... not pretty.  We
must therefore ignore the SIGINT signals until we are sure the
exception handler is active, in the Python callback.

IPython/lib/inputhook.py

@@ -1,453 +1,483 b''
 # coding: utf-8
 """
 Inputhook management for GUI event loop integration.
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2008-2009  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
 #-----------------------------------------------------------------------------
 
 import ctypes
 import os
 import sys
 import warnings
 
 #-----------------------------------------------------------------------------
 # Constants
 #-----------------------------------------------------------------------------
 
 # Constants for identifying the GUI toolkits.
 GUI_WX = 'wx'
 GUI_QT = 'qt'
 GUI_QT4 = 'qt4'
 GUI_GTK = 'gtk'
 GUI_TK = 'tk'
 GUI_OSX = 'osx'
 GUI_GLUT = 'glut'
 GUI_PYGLET = 'pyglet'
 GUI_NONE = 'none' # i.e. disable
 
 #-----------------------------------------------------------------------------
 # Utilities
 #-----------------------------------------------------------------------------
 
 def _stdin_ready_posix():
     """Return True if there's something to read on stdin (posix version)."""
     infds, outfds, erfds = select.select([sys.stdin],[],[],0)
     return bool(infds)
 
 def _stdin_ready_nt():
     """Return True if there's something to read on stdin (nt version)."""
     return msvcrt.kbhit()
 
 def _stdin_ready_other():
     """Return True, assuming there's something to read on stdin."""
     return True #
 
+
+def _ignore_CTRL_C_posix():
+    """Ignore CTRL+C (SIGINT)."""
+    signal.signal(signal.SIGINT, signal.SIG_IGN)
+
+def _allow_CTRL_C_posix():
+    """Take CTRL+C into account (SIGINT)."""
+    signal.signal(signal.SIGINT, signal.default_int_handler)
+
+def _ignore_CTRL_C_other():
+    """Ignore CTRL+C (not implemented)."""
+    pass
+
+def _allow_CTRL_C_other():
+    """Take CTRL+C into account (not implemented)."""
+    pass
+
 if os.name == 'posix':
     import select
+    import signal
     stdin_ready = _stdin_ready_posix
+    ignore_CTRL_C = _ignore_CTRL_C_posix
+    allow_CTRL_C = _allow_CTRL_C_posix
 elif os.name == 'nt':
     import msvcrt
     stdin_ready = _stdin_ready_nt
+    ignore_CTRL_C = _ignore_CTRL_C_other
+    allow_CTRL_C = _allow_CTRL_C_other
 else:
     stdin_ready = _stdin_ready_other
+    ignore_CTRL_C = _ignore_CTRL_C_other
+    allow_CTRL_C = _allow_CTRL_C_other
 
 
 #-----------------------------------------------------------------------------
 # Main InputHookManager class
 #-----------------------------------------------------------------------------
 
 
 class InputHookManager(object):
     """Manage PyOS_InputHook for different GUI toolkits.
 
     This class installs various hooks under ``PyOSInputHook`` to handle
     GUI event loop integration.
     """
     
     def __init__(self):
         self.PYFUNC = ctypes.PYFUNCTYPE(ctypes.c_int)
         self._apps = {}
         self._reset()
 
     def _reset(self):
         self._callback_pyfunctype = None
         self._callback = None
         self._installed = False
         self._current_gui = None
 
     def get_pyos_inputhook(self):
         """Return the current PyOS_InputHook as a ctypes.c_void_p."""
         return ctypes.c_void_p.in_dll(ctypes.pythonapi,"PyOS_InputHook")
 
     def get_pyos_inputhook_as_func(self):
         """Return the current PyOS_InputHook as a ctypes.PYFUNCYPE."""
         return self.PYFUNC.in_dll(ctypes.pythonapi,"PyOS_InputHook")
 
     def set_inputhook(self, callback):
         """Set PyOS_InputHook to callback and return the previous one."""
+        # On platforms with 'readline' support, it's all too likely to
+        # have a KeyboardInterrupt signal delivered *even before* an
+        # initial ``try:`` clause in the callback can be executed, so
+        # we need to disable CTRL+C in this situation.
+        ignore_CTRL_C()
         self._callback = callback
         self._callback_pyfunctype = self.PYFUNC(callback)
         pyos_inputhook_ptr = self.get_pyos_inputhook()
         original = self.get_pyos_inputhook_as_func()
         pyos_inputhook_ptr.value = \
             ctypes.cast(self._callback_pyfunctype, ctypes.c_void_p).value
         self._installed = True
         return original
 
     def clear_inputhook(self, app=None):
         """Set PyOS_InputHook to NULL and return the previous one.
 
         Parameters
         ----------
         app : optional, ignored
           This parameter is allowed only so that clear_inputhook() can be
           called with a similar interface as all the ``enable_*`` methods.  But
           the actual value of the parameter is ignored.  This uniform interface
           makes it easier to have user-level entry points in the main IPython
           app like :meth:`enable_gui`."""
         pyos_inputhook_ptr = self.get_pyos_inputhook()
         original = self.get_pyos_inputhook_as_func()
         pyos_inputhook_ptr.value = ctypes.c_void_p(None).value
+        allow_CTRL_C()
         self._reset()
         return original
 
     def clear_app_refs(self, gui=None):
         """Clear IPython's internal reference to an application instance.
 
         Whenever we create an app for a user on qt4 or wx, we hold a
         reference to the app.  This is needed because in some cases bad things
         can happen if a user doesn't hold a reference themselves.  This
         method is provided to clear the references we are holding.
 
         Parameters
         ----------
         gui : None or str
             If None, clear all app references.  If ('wx', 'qt4') clear
             the app for that toolkit.  References are not held for gtk or tk
             as those toolkits don't have the notion of an app.
         """
         if gui is None:
             self._apps = {}
         elif self._apps.has_key(gui):
             del self._apps[gui]
 
     def enable_wx(self, app=None):
         """Enable event loop integration with wxPython.
 
         Parameters
         ----------
         app : WX Application, optional.
             Running application to use.  If not given, we probe WX for an
             existing application object, and create a new one if none is found.
 
         Notes
         -----
         This methods sets the ``PyOS_InputHook`` for wxPython, which allows
         the wxPython to integrate with terminal based applications like
         IPython.
 
         If ``app`` is not given we probe for an existing one, and return it if
         found.  If no existing app is found, we create an :class:`wx.App` as
         follows::
 
             import wx
             app = wx.App(redirect=False, clearSigInt=False)
         """
         from IPython.lib.inputhookwx import inputhook_wx
         self.set_inputhook(inputhook_wx)
         self._current_gui = GUI_WX
         import wx
         if app is None:
             app = wx.GetApp()
         if app is None:
             app = wx.App(redirect=False, clearSigInt=False)
         app._in_event_loop = True
         self._apps[GUI_WX] = app
         return app
 
     def disable_wx(self):
         """Disable event loop integration with wxPython.
 
         This merely sets PyOS_InputHook to NULL.
         """
         if self._apps.has_key(GUI_WX):
             self._apps[GUI_WX]._in_event_loop = False
         self.clear_inputhook()
 
     def enable_qt4(self, app=None):
         """Enable event loop integration with PyQt4.
         
         Parameters
         ----------
         app : Qt Application, optional.
             Running application to use.  If not given, we probe Qt for an
             existing application object, and create a new one if none is found.
 
         Notes
         -----
         This methods sets the PyOS_InputHook for PyQt4, which allows
         the PyQt4 to integrate with terminal based applications like
         IPython.
 
         If ``app`` is not given we probe for an existing one, and return it if
         found.  If no existing app is found, we create an :class:`QApplication`
         as follows::
 
             from PyQt4 import QtCore
             app = QtGui.QApplication(sys.argv)
         """
         from IPython.lib.inputhookqt4 import create_inputhook_qt4
         app, inputhook_qt4 = create_inputhook_qt4(self, app)
         self.set_inputhook(inputhook_qt4)
 
         self._current_gui = GUI_QT4
         app._in_event_loop = True
         self._apps[GUI_QT4] = app
         return app
 
     def disable_qt4(self):
         """Disable event loop integration with PyQt4.
 
         This merely sets PyOS_InputHook to NULL.
         """
         if self._apps.has_key(GUI_QT4):
             self._apps[GUI_QT4]._in_event_loop = False
         self.clear_inputhook()
 
     def enable_gtk(self, app=None):
         """Enable event loop integration with PyGTK.
 
         Parameters
         ----------
         app : ignored
            Ignored, it's only a placeholder to keep the call signature of all
            gui activation methods consistent, which simplifies the logic of
            supporting magics.
 
         Notes
         -----
         This methods sets the PyOS_InputHook for PyGTK, which allows
         the PyGTK to integrate with terminal based applications like
         IPython.
         """
         import gtk
         try:
             gtk.set_interactive(True)
             self._current_gui = GUI_GTK
         except AttributeError:
             # For older versions of gtk, use our own ctypes version
             from IPython.lib.inputhookgtk import inputhook_gtk
             self.set_inputhook(inputhook_gtk)
             self._current_gui = GUI_GTK
 
     def disable_gtk(self):
         """Disable event loop integration with PyGTK.
         
         This merely sets PyOS_InputHook to NULL.
         """
         self.clear_inputhook()
 
     def enable_tk(self, app=None):
         """Enable event loop integration with Tk.
 
         Parameters
         ----------
         app : toplevel :class:`Tkinter.Tk` widget, optional.
             Running toplevel widget to use.  If not given, we probe Tk for an
             existing one, and create a new one if none is found.
 
         Notes
         -----
         If you have already created a :class:`Tkinter.Tk` object, the only
         thing done by this method is to register with the
         :class:`InputHookManager`, since creating that object automatically
         sets ``PyOS_InputHook``.
         """
         self._current_gui = GUI_TK
         if app is None:
             import Tkinter
             app = Tkinter.Tk()
             app.withdraw()
             self._apps[GUI_TK] = app
             return app
 
     def disable_tk(self):
         """Disable event loop integration with Tkinter.
         
         This merely sets PyOS_InputHook to NULL.
         """
         self.clear_inputhook()
 
 
     def enable_glut(self, app=None):
         """ Enable event loop integration with GLUT.
 
         Parameters
         ----------
 
         app : ignored
             Ignored, it's only a placeholder to keep the call signature of all
             gui activation methods consistent, which simplifies the logic of
             supporting magics.
 
         Notes
         -----
 
         This methods sets the PyOS_InputHook for GLUT, which allows the GLUT to
         integrate with terminal based applications like IPython. Due to GLUT
         limitations, it is currently not possible to start the event loop
         without first creating a window. You should thus not create another
         window but use instead the created one. See 'gui-glut.py' in the
         docs/examples/lib directory.
         
         The default screen mode is set to:
         glut.GLUT_DOUBLE | glut.GLUT_RGBA | glut.GLUT_DEPTH
         """
 
         import OpenGL.GLUT as glut
         from IPython.lib.inputhookglut import glut_display_mode, \
                                               glut_close, glut_display, \
                                               glut_idle, inputhook_glut
 
         if not self._apps.has_key( GUI_GLUT ):
             glut.glutInit( sys.argv )
             glut.glutInitDisplayMode( glut_display_mode )
             # This is specific to freeglut
             if bool(glut.glutSetOption):
                 glut.glutSetOption( glut.GLUT_ACTION_ON_WINDOW_CLOSE,
                                     glut.GLUT_ACTION_GLUTMAINLOOP_RETURNS )
             glut.glutCreateWindow( sys.argv[0] )
             glut.glutReshapeWindow( 1, 1 )
             glut.glutHideWindow( )
             glut.glutWMCloseFunc( glut_close )
             glut.glutDisplayFunc( glut_display )
             glut.glutIdleFunc( glut_idle )
         else:
             glut.glutWMCloseFunc( glut_close )
             glut.glutDisplayFunc( glut_display )
             glut.glutIdleFunc( glut_idle)
         self.set_inputhook( inputhook_glut )
         self._current_gui = GUI_GLUT
         self._apps[GUI_GLUT] = True
 
 
     def disable_glut(self):
         """Disable event loop integration with glut.
         
         This sets PyOS_InputHook to NULL and set the display function to a
         dummy one and set the timer to a dummy timer that will be triggered
         very far in the future.
         """
         import OpenGL.GLUT as glut
         from glut_support import glutMainLoopEvent
 
         glut.glutHideWindow() # This is an event to be processed below
         glutMainLoopEvent()
         self.clear_inputhook()
 
     def enable_pyglet(self, app=None):
         """Enable event loop integration with pyglet.
 
         Parameters
         ----------
         app : ignored
            Ignored, it's only a placeholder to keep the call signature of all
            gui activation methods consistent, which simplifies the logic of
            supporting magics.
 
         Notes
         -----
         This methods sets the ``PyOS_InputHook`` for pyglet, which allows
         pyglet to integrate with terminal based applications like
         IPython.
 
         """
         import pyglet
         from IPython.lib.inputhookpyglet import inputhook_pyglet
         self.set_inputhook(inputhook_pyglet)
         self._current_gui = GUI_PYGLET
         return app
 
     def disable_pyglet(self):
         """Disable event loop integration with pyglet.
 
         This merely sets PyOS_InputHook to NULL.
         """
         self.clear_inputhook()
 
     def current_gui(self):
         """Return a string indicating the currently active GUI or None."""
         return self._current_gui
 
 inputhook_manager = InputHookManager()
 
 enable_wx = inputhook_manager.enable_wx
 disable_wx = inputhook_manager.disable_wx
 enable_qt4 = inputhook_manager.enable_qt4
 disable_qt4 = inputhook_manager.disable_qt4
 enable_gtk = inputhook_manager.enable_gtk
 disable_gtk = inputhook_manager.disable_gtk
 enable_tk = inputhook_manager.enable_tk
 disable_tk = inputhook_manager.disable_tk
 enable_glut = inputhook_manager.enable_glut
 disable_glut = inputhook_manager.disable_glut
 enable_pyglet = inputhook_manager.enable_pyglet
 disable_pyglet = inputhook_manager.disable_pyglet
 clear_inputhook = inputhook_manager.clear_inputhook
 set_inputhook = inputhook_manager.set_inputhook
 current_gui = inputhook_manager.current_gui
 clear_app_refs = inputhook_manager.clear_app_refs
 
 
 # Convenience function to switch amongst them
 def enable_gui(gui=None, app=None):
     """Switch amongst GUI input hooks by name.
 
     This is just a utility wrapper around the methods of the InputHookManager
     object.
 
     Parameters
     ----------
     gui : optional, string or None
       If None (or 'none'), clears input hook, otherwise it must be one
       of the recognized GUI names (see ``GUI_*`` constants in module).
 
     app : optional, existing application object.
       For toolkits that have the concept of a global app, you can supply an
       existing one.  If not given, the toolkit will be probed for one, and if
       none is found, a new one will be created.  Note that GTK does not have
       this concept, and passing an app if `gui`=="GTK" will raise an error.
 
     Returns
     -------
     The output of the underlying gui switch routine, typically the actual
     PyOS_InputHook wrapper object or the GUI toolkit app created, if there was
     one.
     """
     guis = {None: clear_inputhook,
             GUI_NONE: clear_inputhook,
             GUI_OSX: lambda app=False: None,
             GUI_TK: enable_tk,
             GUI_GTK: enable_gtk,
             GUI_WX: enable_wx,
             GUI_QT: enable_qt4, # qt3 not supported
             GUI_QT4: enable_qt4,
             GUI_GLUT: enable_glut,
             GUI_PYGLET: enable_pyglet,
             }
     try:
         gui_hook = guis[gui]
     except KeyError:
         e = "Invalid GUI request %r, valid ones are:%s" % (gui, guis.keys())
         raise ValueError(e)
     return gui_hook(app)
 

IPython/lib/inputhookqt4.py

@@ -1,113 +1,115 b''
 # -*- coding: utf-8 -*-
 """
 Qt4's inputhook support function
 
 Author: Christian Boos
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2011  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
 #-----------------------------------------------------------------------------
 
 from IPython.external.qt_for_kernel import QtCore, QtGui
-from IPython.lib.inputhook import stdin_ready
+from IPython.lib.inputhook import allow_CTRL_C, ignore_CTRL_C, stdin_ready
 
 #-----------------------------------------------------------------------------
 # Code
 #-----------------------------------------------------------------------------
 
 def create_inputhook_qt4(mgr, app=None):
     """Create an input hook for running the Qt4 application event loop.
 
     Parameters
     ----------
     mgr : an InputHookManager
 
     app : Qt Application, optional.
         Running application to use.  If not given, we probe Qt for an
         existing application object, and create a new one if none is found.
 
     Returns
     -------
     A pair consisting of a Qt Application (either the one given or the
     one found or created) and a inputhook.
 
     Notes
     -----
     We use a custom input hook instead of PyQt4's default one, as it
     interacts better with the readline packages (issue #481).
 
     The inputhook function works in tandem with a 'pre_prompt_hook'
     which automatically restores the hook as an inputhook in case the
     latter has been temporarily disabled after having intercepted a
     KeyboardInterrupt.
     """
 
     if app is None:
         app = QtCore.QCoreApplication.instance()
         if app is None:
             app = QtGui.QApplication([" "])
 
     # Re-use previously created inputhook if any
     ip = get_ipython()
     if hasattr(ip, '_inputhook_qt4'):
         return app, ip._inputhook_qt4
 
     # Otherwise create the inputhook_qt4/preprompthook_qt4 pair of
     # hooks (they both share the got_kbdint flag)
 
     got_kbdint = [False]
 
     def inputhook_qt4():
         """PyOS_InputHook python hook for Qt4.
 
         Process pending Qt events and if there's no pending keyboard
         input, spend a short slice of time (50ms) running the Qt event
         loop.
 
         As a Python ctypes callback can't raise an exception, we catch
         the KeyboardInterrupt and temporarily deactivate the hook,
         which will let a *second* CTRL+C be processed normally and go
         back to a clean prompt line.
         """
         try:
+            allow_CTRL_C()
             app = QtCore.QCoreApplication.instance()
             app.processEvents(QtCore.QEventLoop.AllEvents, 300)
             if not stdin_ready():
                 timer = QtCore.QTimer()
                 timer.timeout.connect(app.quit)
                 while not stdin_ready():
                     timer.start(50)
                     app.exec_()
                     timer.stop()
         except KeyboardInterrupt:
+            ignore_CTRL_C()
             got_kbdint[0] = True
-            mgr.clear_inputhook()
             print("\nKeyboardInterrupt - qt4 event loop interrupted!"
                   "\n  * hit CTRL+C again to clear the prompt"
                   "\n  * use '%gui none' to disable the event loop"
                   " permanently"
                   "\n    and '%gui qt4' to re-enable it later")
+            mgr.clear_inputhook()
         return 0
 
     def preprompthook_qt4(ishell):
         """'pre_prompt_hook' used to restore the Qt4 input hook
 
         (in case the latter was temporarily deactivated after a
         CTRL+C)
         """
         if got_kbdint[0]:
             mgr.set_inputhook(inputhook_qt4)
         got_kbdint[0] = False
 
     ip._inputhook_qt4 = inputhook_qt4
     ip.set_hook('pre_prompt_hook', preprompthook_qt4)
 
     return app, inputhook_qt4