From 55129be9697868c906130c945d2bd27087654f2b 2013-04-29 23:19:35
From: Fernando Perez <fernando.perez@berkeley.edu>
Date: 2013-04-29 23:19:35
Subject: [PATCH] Merge pull request #3219 from siyuz/ctrl-c_clear_line

Workaround so only one CTRL-C is required for a new prompt in --gui=qt.
---

diff --git a/IPython/lib/inputhookqt4.py b/IPython/lib/inputhookqt4.py
index eae4f44..4770e0a 100644
--- a/IPython/lib/inputhookqt4.py
+++ b/IPython/lib/inputhookqt4.py
@@ -16,11 +16,23 @@ Author: Christian Boos
 # Imports
 #-----------------------------------------------------------------------------
 
+import os
+import signal
+import time
+import threading
+
 from IPython.core.interactiveshell import InteractiveShell
 from IPython.external.qt_for_kernel import QtCore, QtGui
 from IPython.lib.inputhook import allow_CTRL_C, ignore_CTRL_C, stdin_ready
 
 #-----------------------------------------------------------------------------
+# Module Globals
+#-----------------------------------------------------------------------------
+
+got_kbdint = False
+sigint_timer = None
+
+#-----------------------------------------------------------------------------
 # Code
 #-----------------------------------------------------------------------------
 
@@ -64,8 +76,6 @@ def create_inputhook_qt4(mgr, app=None):
     # 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.
 
@@ -114,10 +124,31 @@ def create_inputhook_qt4(mgr, app=None):
                     event_loop.exec_()
                     timer.stop()
         except KeyboardInterrupt:
+            global got_kbdint, sigint_timer
+
             ignore_CTRL_C()
-            got_kbdint[0] = True
-            print("\nKeyboardInterrupt - Ctrl-C again for new prompt")
+            got_kbdint = True
             mgr.clear_inputhook()
+
+            # This generates a second SIGINT so the user doesn't have to
+            # press CTRL+C twice to get a clean prompt.
+            #
+            # Since we can't catch the resulting KeyboardInterrupt here
+            # (because this is a ctypes callback), we use a timer to
+            # generate the SIGINT after we leave this callback.
+            #
+            # Unfortunately this doesn't work on Windows (SIGINT kills
+            # Python and CTRL_C_EVENT doesn't work).
+            if(os.name == 'posix'):
+                pid = os.getpid()
+                if(not sigint_timer):
+                    sigint_timer = threading.Timer(.01, os.kill,
+                                         args=[pid, signal.SIGINT] )
+                    sigint_timer.start()
+            else:
+                print("\nKeyboardInterrupt - Ctrl-C again for new prompt")
+
+
         except: # NO exceptions are allowed to escape from a ctypes callback
             ignore_CTRL_C()
             from traceback import print_exc
@@ -134,9 +165,15 @@ def create_inputhook_qt4(mgr, app=None):
         (in case the latter was temporarily deactivated after a
         CTRL+C)
         """
-        if got_kbdint[0]:
+        global got_kbdint, sigint_timer
+
+        if(sigint_timer):
+            sigint_timer.cancel()
+            sigint_timer = None
+
+        if got_kbdint:
             mgr.set_inputhook(inputhook_qt4)
-        got_kbdint[0] = False
+        got_kbdint = False
 
     ip._inputhook_qt4 = inputhook_qt4
     ip.set_hook('pre_prompt_hook', preprompthook_qt4)