inputhook: improve CTRL+C handling with qt4

Allow a first CTRL+C to interrupt the qt4 event loop
and a second to trigger a KeyboardInterrupt.

IPython/lib/inputhook.py

@@ -1,464 +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'
 
 #-----------------------------------------------------------------------------
 # Utilities
 #-----------------------------------------------------------------------------
 
 def stdin_ready():
     if os.name == 'posix':
         import select
         infds, outfds, erfds = select.select([sys.stdin],[],[],0)
         if infds:
             return True
         else:
             return False
     elif os.name == 'nt':
         import msvcrt
         return msvcrt.kbhit()
     return True # assume there's something so that we won't wait forever
 
 
 #-----------------------------------------------------------------------------
 # 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."""
         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
         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.external.qt_for_kernel import QtCore, QtGui
+        from IPython.core import ipapi
 
         if app is None:
             app = QtCore.QCoreApplication.instance()
         if app is None:
             app = QtGui.QApplication([" "])
 
-        # Always use the following input hook instead of PyQt4's
-        # default one, as it interacts better with readline packages
-        # (issue #481)
+        # Always use a custom input hook instead of PyQt4's default
+        # one, as it interacts better with readline packages (issue
+        # #481).
+
+        # Note that we can't let KeyboardInterrupt escape from that
+        # hook, (no exception can't be raised from within a ctypes
+        # python callback). We need to make a compromise: a trapped
+        # KeyboardInterrupt will prevent the input hook to re-enter
+        # the exec loop, until we start over with a new prompt line.
+        # This means one needs a double CTRL+C to get back to the
+        # prompt.
+
+        got_kbdint = [False]
+
+        def preprompthook_qt4(self):
+            got_kbdint[0] = False
+        ipapi.get().set_hook('pre_prompt_hook', preprompthook_qt4)
 
         def inputhook_qt4():
             try:
+                if got_kbdint[0]:
+                    return 0
                 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:
-                pass
+                got_kbdint[0] = True
+                print("\n(event loop interrupted - "
+                      "hit CTRL+C again to clear the prompt)")
             return 0
         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, 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_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)