* Added 'started_listening' and 'stopped_listening' signals to QtKernelManager. The FrontendWidget listens for these signals.

* Created a metaclass to permit inheriting from both HasTraits and QObject
* Made 'continuation_prompt' a protected variable of ConsoleWidget for API consistency
* Made FrontendWidget's constructor consistent with QWidget conventions.

IPython/frontend/qt/util.py

@@ -0,0 +1,25 b''
+""" Defines miscellaneous Qt-related helper classes and functions.
+"""
+
+# System library imports.
+from PyQt4 import QtCore
+
+# IPython imports.
+from IPython.utils.traitlets import HasTraits
+
+
+MetaHasTraits = type(HasTraits)
+MetaQObject = type(QtCore.QObject)
+
+class MetaQObjectHasTraits(MetaQObject, MetaHasTraits):
+    """ A metaclass that inherits from the metaclasses of both HasTraits and
+        QObject. 
+
+        Using this metaclass allows a class to inherit from both HasTraits and
+        QObject. See QtKernelManager for an example.
+    """
+
+    def __init__(cls, name, bases, dct):
+        MetaQObject.__init__(cls, name, bases, dct)
+        MetaHasTraits.__init__(cls, name, bases, dct)
+        

IPython/frontend/qt/console/console_widget.py

@@ -1,674 +1,688 b''
 # Standard library imports
 import re
 
 # System library imports
 from PyQt4 import QtCore, QtGui
 
 # Local imports
 from completion_widget import CompletionWidget
 
 
 class AnsiCodeProcessor(object):
     """ Translates ANSI escape codes into readable attributes.
     """
 
     def __init__(self):
         self.ansi_colors = ( # Normal, Bright/Light
                              ('#000000', '#7f7f7f'), # 0: black
                              ('#cd0000', '#ff0000'), # 1: red
                              ('#00cd00', '#00ff00'), # 2: green
                              ('#cdcd00', '#ffff00'), # 3: yellow
                              ('#0000ee', '#0000ff'), # 4: blue
                              ('#cd00cd', '#ff00ff'), # 5: magenta
                              ('#00cdcd', '#00ffff'), # 6: cyan
                              ('#e5e5e5', '#ffffff')) # 7: white
         self.reset()
         
     def set_code(self, code):
         """ Set attributes based on code.
         """
         if code == 0:
             self.reset()
         elif code == 1:
             self.intensity = 1
             self.bold = True
         elif code == 3:
             self.italic = True
         elif code == 4:
             self.underline = True
         elif code == 22:
             self.intensity = 0
             self.bold = False
         elif code == 23:
             self.italic = False
         elif code == 24:
             self.underline = False
         elif code >= 30 and code <= 37:
             self.foreground_color = code - 30
         elif code == 39:
             self.foreground_color = None
         elif code >= 40 and code <= 47:
             self.background_color = code - 40
         elif code == 49:
             self.background_color = None
         
     def reset(self):
         """ Reset attributs to their default values.
         """
         self.intensity = 0
         self.italic = False
         self.bold = False
         self.underline = False
         self.foreground_color = None
         self.background_color = None
 
 
 class QtAnsiCodeProcessor(AnsiCodeProcessor):
     """ Translates ANSI escape codes into QTextCharFormats.
     """
     
     def get_format(self):
         """ Returns a QTextCharFormat that encodes the current style attributes.
         """
         format = QtGui.QTextCharFormat()
 
         # Set foreground color
         if self.foreground_color is not None:
             color = self.ansi_colors[self.foreground_color][self.intensity]
             format.setForeground(QtGui.QColor(color))
 
         # Set background color
         if self.background_color is not None:
             color = self.ansi_colors[self.background_color][self.intensity]
             format.setBackground(QtGui.QColor(color))
 
         # Set font weight/style options
         if self.bold:
             format.setFontWeight(QtGui.QFont.Bold)
         else:
             format.setFontWeight(QtGui.QFont.Normal)
         format.setFontItalic(self.italic)
         format.setFontUnderline(self.underline)
 
         return format
 
 
 class ConsoleWidget(QtGui.QPlainTextEdit):
     """ Base class for console-type widgets. This class is mainly concerned with
         dealing with the prompt, keeping the cursor inside the editing line, and
         handling ANSI escape sequences.
     """
 
     # Regex to match ANSI escape sequences
     _ansi_pattern = re.compile('\x01?\x1b\[(.*?)m\x02?')
     
     # When ctrl is pressed, map certain keys to other keys (without the ctrl):
     _ctrl_down_remap = { QtCore.Qt.Key_B : QtCore.Qt.Key_Left,
                          QtCore.Qt.Key_F : QtCore.Qt.Key_Right,
                          QtCore.Qt.Key_A : QtCore.Qt.Key_Home,
                          QtCore.Qt.Key_E : QtCore.Qt.Key_End,
                          QtCore.Qt.Key_P : QtCore.Qt.Key_Up,
                          QtCore.Qt.Key_N : QtCore.Qt.Key_Down,
                          QtCore.Qt.Key_D : QtCore.Qt.Key_Delete, }
 
     #---------------------------------------------------------------------------
     # 'QWidget' interface
     #---------------------------------------------------------------------------
 
     def __init__(self, parent=None):
         QtGui.QPlainTextEdit.__init__(self, parent)
 
         # Initialize public and protected variables
         self.ansi_codes = True
         self.buffer_size = 500
-        self.continuation_prompt = '> '
         self.gui_completion = True
         self._ansi_processor = QtAnsiCodeProcessor()
         self._completion_widget = CompletionWidget(self)
+        self._continuation_prompt = '> '
         self._executing = False
         self._prompt = ''
         self._prompt_pos = 0
         self._reading = False
 
         # Set a monospaced font
         point_size = QtGui.QApplication.font().pointSize()
         font = QtGui.QFont('Monospace', point_size)
         font.setStyleHint(QtGui.QFont.TypeWriter)
         self._completion_widget.setFont(font)
         self.document().setDefaultFont(font)
 
         # Define a custom context menu
         self._context_menu = QtGui.QMenu(self)
 
         copy_action = QtGui.QAction('Copy', self)
         copy_action.triggered.connect(self.copy)
         self.copyAvailable.connect(copy_action.setEnabled)
         self._context_menu.addAction(copy_action)
 
         self._paste_action = QtGui.QAction('Paste', self)
         self._paste_action.triggered.connect(self.paste)
         self._context_menu.addAction(self._paste_action)
         self._context_menu.addSeparator()
 
         select_all_action = QtGui.QAction('Select All', self)
         select_all_action.triggered.connect(self.selectAll)
         self._context_menu.addAction(select_all_action)
 
     def contextMenuEvent(self, event):
         """ Reimplemented to create a menu without destructive actions like
             'Cut' and 'Delete'.
         """
         clipboard_empty = QtGui.QApplication.clipboard().text().isEmpty()
         self._paste_action.setEnabled(not clipboard_empty)
         
         self._context_menu.exec_(event.globalPos())
 
     def keyPressEvent(self, event):
         """ Reimplemented to create a console-like interface.
         """
         intercepted = False
         cursor = self.textCursor()
         position = cursor.position()
         key = event.key()
         ctrl_down = event.modifiers() & QtCore.Qt.ControlModifier
         alt_down = event.modifiers() & QtCore.Qt.AltModifier
         shift_down = event.modifiers() & QtCore.Qt.ShiftModifier
 
         # Even though we have reimplemented 'paste', the C++ level slot is still
         # called by Qt. So we intercept the key press here.
         if event.matches(QtGui.QKeySequence.Paste):
             self.paste()
             intercepted = True
 
         elif ctrl_down:
             if key in self._ctrl_down_remap:
                 ctrl_down = False
                 key = self._ctrl_down_remap[key]
                 event = QtGui.QKeyEvent(QtCore.QEvent.KeyPress, key, 
                                         QtCore.Qt.NoModifier)
 
             elif key == QtCore.Qt.Key_K:
                 if self._in_buffer(position):
                     cursor.movePosition(QtGui.QTextCursor.EndOfLine,
                                         QtGui.QTextCursor.KeepAnchor)
                     cursor.removeSelectedText()
                 intercepted = True
 
             elif key == QtCore.Qt.Key_Y:
                 self.paste()
                 intercepted = True
 
         elif alt_down:
             if key == QtCore.Qt.Key_B:
                 self.setTextCursor(self._get_word_start_cursor(position))
                 intercepted = True
                 
             elif key == QtCore.Qt.Key_F:
                 self.setTextCursor(self._get_word_end_cursor(position))
                 intercepted = True
 
             elif key == QtCore.Qt.Key_Backspace:
                 cursor = self._get_word_start_cursor(position)
                 cursor.setPosition(position, QtGui.QTextCursor.KeepAnchor)
                 cursor.removeSelectedText()
                 intercepted = True
 
             elif key == QtCore.Qt.Key_D:
                 cursor = self._get_word_end_cursor(position)
                 cursor.setPosition(position, QtGui.QTextCursor.KeepAnchor)
                 cursor.removeSelectedText()
                 intercepted = True
 
         if self._completion_widget.isVisible():
             self._completion_widget.keyPressEvent(event)
             intercepted = event.isAccepted()
         
         else:
             if key in (QtCore.Qt.Key_Return, QtCore.Qt.Key_Enter):
                 if self._reading:
                     self._reading = False
                 elif not self._executing:
                     self.execute(interactive=True)
                 intercepted = True
 
             elif key == QtCore.Qt.Key_Up:
                 if self._reading or not self._up_pressed():
                     intercepted = True
                 else:
                     prompt_line = self._get_prompt_cursor().blockNumber()
                     intercepted = cursor.blockNumber() <= prompt_line
 
             elif key == QtCore.Qt.Key_Down:
                 if self._reading or not self._down_pressed():
                     intercepted = True
                 else:
                     end_line = self._get_end_cursor().blockNumber()
                     intercepted = cursor.blockNumber() == end_line
 
             elif key == QtCore.Qt.Key_Tab:
                 if self._reading:
                     intercepted = False
                 else:
                     intercepted = not self._tab_pressed()
 
             elif key == QtCore.Qt.Key_Left:
                 intercepted = not self._in_buffer(position - 1)
 
             elif key == QtCore.Qt.Key_Home:
                 cursor.movePosition(QtGui.QTextCursor.StartOfLine)
                 start_pos = cursor.position()
                 start_line = cursor.blockNumber()
                 if start_line == self._get_prompt_cursor().blockNumber():
                     start_pos += len(self._prompt)
                 else:
-                    start_pos += len(self.continuation_prompt)
+                    start_pos += len(self._continuation_prompt)
                 if shift_down and self._in_buffer(position):
                     self._set_selection(position, start_pos)
                 else:
                     self._set_position(start_pos)
                 intercepted = True
 
             elif key == QtCore.Qt.Key_Backspace and not alt_down:
 
                 # Line deletion (remove continuation prompt)
-                len_prompt = len(self.continuation_prompt)
+                len_prompt = len(self._continuation_prompt)
                 if cursor.columnNumber() == len_prompt and \
                         position != self._prompt_pos:
                     cursor.setPosition(position - len_prompt, 
                                        QtGui.QTextCursor.KeepAnchor)
                     cursor.removeSelectedText()
 
                 # Regular backwards deletion
                 else:
                     anchor = cursor.anchor()
                     if anchor == position:
                         intercepted = not self._in_buffer(position - 1)
                     else:
                         intercepted = not self._in_buffer(min(anchor, position))
 
             elif key == QtCore.Qt.Key_Delete:
                 anchor = cursor.anchor()
                 intercepted = not self._in_buffer(min(anchor, position))
 
         # Don't move cursor if control is down to allow copy-paste using
         # the keyboard in any part of the buffer.
         if not ctrl_down:
             self._keep_cursor_in_buffer()
 
         if not intercepted:
             QtGui.QPlainTextEdit.keyPressEvent(self, event)
 
     #--------------------------------------------------------------------------
     # 'QPlainTextEdit' interface
     #--------------------------------------------------------------------------
 
     def appendPlainText(self, text):
         """ Reimplemented to not append text as a new paragraph, which doesn't
             make sense for a console widget. Also, if enabled, handle ANSI
             codes.
         """
         cursor = self.textCursor()
         cursor.movePosition(QtGui.QTextCursor.End)
 
         if self.ansi_codes:
             format = QtGui.QTextCharFormat()
             previous_end = 0
             for match in self._ansi_pattern.finditer(text):
                 cursor.insertText(text[previous_end:match.start()], format)
                 previous_end = match.end()
                 for code in match.group(1).split(';'):
                     self._ansi_processor.set_code(int(code))
                 format = self._ansi_processor.get_format()
             cursor.insertText(text[previous_end:], format)
         else:
             cursor.insertText(text)
 
+    def clear(self, keep_input=False):
+        """ Reimplemented to write a new prompt. If 'keep_input' is set,
+            restores the old input buffer when the new prompt is written.
+        """
+        super(ConsoleWidget, self).clear()
+
+        if keep_input:
+            input_buffer = self.input_buffer
+        self._show_prompt()
+        if keep_input:
+            self.input_buffer = input_buffer
+
     def paste(self):
         """ Reimplemented to ensure that text is pasted in the editing region.
         """
         self._keep_cursor_in_buffer()
         QtGui.QPlainTextEdit.paste(self)
 
     def print_(self, printer):
-        """ Reimplemented to work around bug in PyQt where the C++ level
-            'print_' slot has the wrong signature.
+        """ Reimplemented to work around a bug in PyQt: the C++ level 'print_'
+            slot has the wrong signature.
         """
         QtGui.QPlainTextEdit.print_(self, printer)
 
     #---------------------------------------------------------------------------
     # 'ConsoleWidget' public interface
     #---------------------------------------------------------------------------
 
     def execute(self, interactive=False):
         """ Execute the text in the input buffer. Returns whether the input
             buffer was completely processed and a new prompt created.
         """
         self.appendPlainText('\n')
         self._executing_input_buffer = self.input_buffer
         self._executing = True
         self._prompt_finished()
         return self._execute(interactive=interactive)
 
     def _get_input_buffer(self):
         # If we're executing, the input buffer may not even exist anymore due
         # the limit imposed by 'buffer_size'. Therefore, we store it.
         if self._executing:
             return self._executing_input_buffer
 
         cursor = self._get_end_cursor()
         cursor.setPosition(self._prompt_pos, QtGui.QTextCursor.KeepAnchor)
 
         # Use QTextDocumentFragment intermediate object because it strips
         # out the Unicode line break characters that Qt insists on inserting.
         input_buffer = str(cursor.selection().toPlainText())
 
         # Strip out continuation prompts
-        return input_buffer.replace('\n' + self.continuation_prompt, '\n')
+        return input_buffer.replace('\n' + self._continuation_prompt, '\n')
 
     def _set_input_buffer(self, string):
         # Add continuation prompts where necessary
         lines = string.splitlines()
         for i in xrange(1, len(lines)):
-            lines[i] = self.continuation_prompt + lines[i]
+            lines[i] = self._continuation_prompt + lines[i]
         string = '\n'.join(lines)
 
         # Replace buffer with new text
         cursor = self._get_end_cursor()
         cursor.setPosition(self._prompt_pos, QtGui.QTextCursor.KeepAnchor)
         cursor.insertText(string)
         self.moveCursor(QtGui.QTextCursor.End)
 
     input_buffer = property(_get_input_buffer, _set_input_buffer)
 
     def _get_input_buffer_cursor_line(self):
         if self._executing:
             return None
         cursor = self.textCursor()
         if cursor.position() >= self._prompt_pos:
             text = str(cursor.block().text())
             if cursor.blockNumber() == self._get_prompt_cursor().blockNumber():
                 return text[len(self._prompt):]
             else:
-                return text[len(self.continuation_prompt):]
+                return text[len(self._continuation_prompt):]
         else:
             return None
 
     input_buffer_cursor_line = property(_get_input_buffer_cursor_line)
 
     #---------------------------------------------------------------------------
     # 'ConsoleWidget' abstract interface
     #---------------------------------------------------------------------------
 
     def _execute(self, interactive):
         """ Called to execute the input buffer. When triggered by an the enter
             key press, 'interactive' is True; otherwise, it is False. Returns
             whether the input buffer was completely processed and a new prompt
             created.
         """
         raise NotImplementedError
 
     def _prompt_started_hook(self):
         """ Called immediately after a new prompt is displayed.
         """
         pass
 
     def _prompt_finished_hook(self):
         """ Called immediately after a prompt is finished, i.e. when some input
             will be processed and a new prompt displayed.
         """
         pass
 
     def _up_pressed(self):
         """ Called when the up key is pressed. Returns whether to continue
             processing the event.
         """
         return True
 
     def _down_pressed(self):
         """ Called when the down key is pressed. Returns whether to continue
             processing the event.
         """
         return True
 
     def _tab_pressed(self):
         """ Called when the tab key is pressed. Returns whether to continue
             processing the event.
         """
         return False
 
     #--------------------------------------------------------------------------
     # 'ConsoleWidget' protected interface
     #--------------------------------------------------------------------------
 
     def _complete_with_items(self, cursor, items):
         """ Performs completion with 'items' at the specified cursor location.
         """
         if len(items) == 1:
             cursor.setPosition(self.textCursor().position(), 
                                QtGui.QTextCursor.KeepAnchor)
             cursor.insertText(items[0])
         elif len(items) > 1:
             if self.gui_completion:
                 self._completion_widget.show_items(cursor, items) 
             else:
                 text = '\n'.join(items) + '\n'
                 self._write_text_keeping_prompt(text)
                 
     def _get_end_cursor(self):
         """ Convenience method that returns a cursor for the last character.
         """
         cursor = self.textCursor()
         cursor.movePosition(QtGui.QTextCursor.End)
         return cursor
 
     def _get_prompt_cursor(self):
         """ Convenience method that returns a cursor for the prompt position.
         """
         cursor = self.textCursor()
         cursor.setPosition(self._prompt_pos)
         return cursor
 
     def _get_selection_cursor(self, start, end):
         """ Convenience method that returns a cursor with text selected between
             the positions 'start' and 'end'.
         """
         cursor = self.textCursor()
         cursor.setPosition(start)
         cursor.setPosition(end, QtGui.QTextCursor.KeepAnchor)
         return cursor
 
     def _get_word_start_cursor(self, position):
         """ Find the start of the word to the left the given position. If a
             sequence of non-word characters precedes the first word, skip over
             them. (This emulates the behavior of bash, emacs, etc.)
         """
         document = self.document()
         position -= 1
         while self._in_buffer(position) and \
                 not document.characterAt(position).isLetterOrNumber():
             position -= 1
         while self._in_buffer(position) and \
                 document.characterAt(position).isLetterOrNumber():
             position -= 1
         cursor = self.textCursor()
         cursor.setPosition(position + 1)
         return cursor
 
     def _get_word_end_cursor(self, position):
         """ Find the end of the word to the right the given position. If a
             sequence of non-word characters precedes the first word, skip over
             them. (This emulates the behavior of bash, emacs, etc.)
         """
         document = self.document()
         end = self._get_end_cursor().position()
         while position < end and \
                 not document.characterAt(position).isLetterOrNumber():
             position += 1
         while position < end and \
                 document.characterAt(position).isLetterOrNumber():
             position += 1
         cursor = self.textCursor()
         cursor.setPosition(position)
         return cursor
 
     def _prompt_started(self):
         """ Called immediately after a new prompt is displayed.
         """
         # Temporarily disable the maximum block count to permit undo/redo.
         self.setMaximumBlockCount(0)
         self.setUndoRedoEnabled(True)
 
         self.setReadOnly(False)
         self.moveCursor(QtGui.QTextCursor.End)
         self.centerCursor()
 
         self._executing = False
         self._prompt_started_hook()
 
     def _prompt_finished(self):
         """ Called immediately after a prompt is finished, i.e. when some input
             will be processed and a new prompt displayed.
         """
         # This has the (desired) side effect of disabling the undo/redo history.
         self.setMaximumBlockCount(self.buffer_size)
 
         self.setReadOnly(True)
         self._prompt_finished_hook()
 
     def _set_position(self, position):
         """ Convenience method to set the position of the cursor.
         """
         cursor = self.textCursor()
         cursor.setPosition(position)
         self.setTextCursor(cursor)
 
     def _set_selection(self, start, end):
         """ Convenience method to set the current selected text.
         """
         self.setTextCursor(self._get_selection_cursor(start, end))
 
-    def _show_prompt(self, prompt):
-        """ Writes a new prompt at the end of the buffer.
+    def _show_prompt(self, prompt=None):
+        """ Writes a new prompt at the end of the buffer. If 'prompt' is not
+            specified, uses the previous prompt.
         """
-        self.appendPlainText('\n' + prompt)
-        self._prompt = prompt
+        if prompt is not None:
+            self._prompt = prompt
+        self.appendPlainText('\n' + self._prompt)
         self._prompt_pos = self._get_end_cursor().position()
         self._prompt_started()
 
     def _show_continuation_prompt(self):
         """ Writes a new continuation prompt at the end of the buffer.
         """
-        self.appendPlainText(self.continuation_prompt)
+        self.appendPlainText(self._continuation_prompt)
         self._prompt_started()
 
     def _write_text_keeping_prompt(self, text):
         """ Writes 'text' after the current prompt, then restores the old prompt
             with its old input buffer.
         """
         input_buffer = self.input_buffer
         self.appendPlainText('\n')
         self._prompt_finished()
 
         self.appendPlainText(text)
-        self._show_prompt(self._prompt)
+        self._show_prompt()
         self.input_buffer = input_buffer
 
     def _in_buffer(self, position):
         """ Returns whether the given position is inside the editing region.
         """
         return position >= self._prompt_pos
 
     def _keep_cursor_in_buffer(self):
         """ Ensures that the cursor is inside the editing region. Returns
             whether the cursor was moved.
         """
         cursor = self.textCursor()
         if cursor.position() < self._prompt_pos:
             cursor.movePosition(QtGui.QTextCursor.End)
             self.setTextCursor(cursor)
             return True
         else:
             return False
 
 
 class HistoryConsoleWidget(ConsoleWidget):
     """ A ConsoleWidget that keeps a history of the commands that have been
         executed.
     """
     
     #---------------------------------------------------------------------------
     # 'QWidget' interface
     #---------------------------------------------------------------------------
 
     def __init__(self, parent=None):
         super(HistoryConsoleWidget, self).__init__(parent)
 
         self._history = []
         self._history_index = 0
 
     #---------------------------------------------------------------------------
     # 'ConsoleWidget' public interface
     #---------------------------------------------------------------------------
 
     def execute(self, interactive=False):
         """ Reimplemented to the store history.
         """
         stripped = self.input_buffer.rstrip()
         executed = super(HistoryConsoleWidget, self).execute(interactive)
         if executed:
             self._history.append(stripped)
             self._history_index = len(self._history)
         return executed
 
     #---------------------------------------------------------------------------
     # 'ConsoleWidget' abstract interface
     #---------------------------------------------------------------------------
 
     def _up_pressed(self):
         """ Called when the up key is pressed. Returns whether to continue
             processing the event.
         """
         prompt_cursor = self._get_prompt_cursor()
         if self.textCursor().blockNumber() == prompt_cursor.blockNumber():
             self.history_previous()
 
             # Go to the first line of prompt for seemless history scrolling.
             cursor = self._get_prompt_cursor()
             cursor.movePosition(QtGui.QTextCursor.EndOfLine)
             self.setTextCursor(cursor)
 
             return False
         return True
 
     def _down_pressed(self):
         """ Called when the down key is pressed. Returns whether to continue
             processing the event.
         """
         end_cursor = self._get_end_cursor()
         if self.textCursor().blockNumber() == end_cursor.blockNumber():
             self.history_next()
             return False
         return True
 
     #---------------------------------------------------------------------------
     # 'HistoryConsoleWidget' interface
     #---------------------------------------------------------------------------
 
     def history_previous(self):
         """ If possible, set the input buffer to the previous item in the
             history.
         """
         if self._history_index > 0:
             self._history_index -= 1
             self.input_buffer = self._history[self._history_index]
 
     def history_next(self):
         """ Set the input buffer to the next item in the history, or a blank
             line if there is no subsequent item.
         """
         if self._history_index < len(self._history):
             self._history_index += 1
             if self._history_index < len(self._history):
                 self.input_buffer = self._history[self._history_index]
             else:
                 self.input_buffer = ''

IPython/frontend/qt/console/frontend_widget.py

@@ -1,276 +1,302 b''
 # System library imports
 from pygments.lexers import PythonLexer
 from PyQt4 import QtCore, QtGui
 import zmq
 
 # Local imports
 from IPython.core.blockbreaker import BlockBreaker
 from call_tip_widget import CallTipWidget
 from completion_lexer import CompletionLexer
 from console_widget import HistoryConsoleWidget
 from pygments_highlighter import PygmentsHighlighter
 
 
 class FrontendHighlighter(PygmentsHighlighter):
     """ A Python PygmentsHighlighter that can be turned on and off and which 
         knows about continuation prompts.
     """
 
     def __init__(self, frontend):
         PygmentsHighlighter.__init__(self, frontend.document(), PythonLexer())
         self._current_offset = 0
         self._frontend = frontend
         self.highlighting_on = False
 
     def highlightBlock(self, qstring):
         """ Highlight a block of text. Reimplemented to highlight selectively.
         """
         if self.highlighting_on:
-            for prompt in (self._frontend._prompt, 
-                           self._frontend.continuation_prompt):
+            for prompt in (self._frontend._continuation_prompt,
+                           self._frontend._prompt):                           
                 if qstring.startsWith(prompt):
                     qstring.remove(0, len(prompt))
                     self._current_offset = len(prompt)
                     break
             PygmentsHighlighter.highlightBlock(self, qstring)
 
     def setFormat(self, start, count, format):
         """ Reimplemented to avoid highlighting continuation prompts.
         """
         start += self._current_offset
         PygmentsHighlighter.setFormat(self, start, count, format)
 
 
 class FrontendWidget(HistoryConsoleWidget):
     """ A Qt frontend for a generic Python kernel.
     """
 
     # Emitted when an 'execute_reply' is received from the kernel.
     executed = QtCore.pyqtSignal(object)
 
     #---------------------------------------------------------------------------
     # 'QWidget' interface
     #---------------------------------------------------------------------------
     
-    def __init__(self, kernel_manager, parent=None):
+    def __init__(self, parent=None):
         super(FrontendWidget, self).__init__(parent)
 
+        # ConsoleWidget protected variables.
+        self._continuation_prompt = '... '
+        self._prompt = '>>> '
+
+        # FrontendWidget protected variables.
         self._blockbreaker = BlockBreaker(input_mode='replace')
         self._call_tip_widget = CallTipWidget(self)
         self._completion_lexer = CompletionLexer(PythonLexer())
         self._hidden = True
         self._highlighter = FrontendHighlighter(self)
         self._kernel_manager = None
 
-        self.continuation_prompt = '... '
-        self.kernel_manager = kernel_manager
-
         self.document().contentsChange.connect(self._document_contents_change)
 
     def focusOutEvent(self, event):
         """ Reimplemented to hide calltips.
         """
         self._call_tip_widget.hide()
         return super(FrontendWidget, self).focusOutEvent(event)
 
     def keyPressEvent(self, event):
         """ Reimplemented to hide calltips.
         """
         if event.key() == QtCore.Qt.Key_Escape:
             self._call_tip_widget.hide()
         return super(FrontendWidget, self).keyPressEvent(event)
 
     #---------------------------------------------------------------------------
     # 'ConsoleWidget' abstract interface
     #---------------------------------------------------------------------------
 
     def _execute(self, interactive):
         """ Called to execute the input buffer. When triggered by an the enter
             key press, 'interactive' is True; otherwise, it is False. Returns
             whether the input buffer was completely processed and a new prompt
             created.
         """
         return self.execute_source(self.input_buffer, interactive=interactive)
         
     def _prompt_started_hook(self):
         """ Called immediately after a new prompt is displayed.
         """
         self._highlighter.highlighting_on = True
 
     def _prompt_finished_hook(self):
         """ Called immediately after a prompt is finished, i.e. when some input
             will be processed and a new prompt displayed.
         """
         self._highlighter.highlighting_on = False
 
     def _tab_pressed(self):
         """ Called when the tab key is pressed. Returns whether to continue
             processing the event.
         """
         self._keep_cursor_in_buffer()
         cursor = self.textCursor()
         if not self._complete():
             cursor.insertText('    ')
         return False
 
     #---------------------------------------------------------------------------
     # 'FrontendWidget' interface
     #---------------------------------------------------------------------------
 
     def execute_source(self, source, hidden=False, interactive=False):
         """ Execute a string containing Python code. If 'hidden', no output is
             shown. Returns whether the source executed (i.e., returns True only
             if no more input is necessary).
         """
         self._blockbreaker.push(source)
         executed = self._blockbreaker.interactive_block_ready()
         if executed:
             self.kernel_manager.xreq_channel.execute(source)
             self._hidden = hidden
         else:
             self._show_continuation_prompt()
             self.appendPlainText(' ' * self._blockbreaker.indent_spaces)
         return executed
 
     def execute_file(self, path, hidden=False):
         """ Attempts to execute file with 'path'. If 'hidden', no output is
             shown.
         """
         self.execute_source('run %s' % path, hidden=hidden)
 
     def _get_kernel_manager(self):
         """ Returns the current kernel manager.
         """
         return self._kernel_manager
 
     def _set_kernel_manager(self, kernel_manager):
-        """ Sets a new kernel manager, configuring its channels as necessary.
+        """ Disconnect from the current kernel manager (if any) and set a new
+            kernel manager.
         """
-        # Disconnect the old kernel manager.
+        # Disconnect the old kernel manager, if necessary.
         if self._kernel_manager is not None:
+            self._kernel_manager.started_listening.disconnect(
+                self._started_listening)
+            self._kernel_manager.stopped_listening.disconnect(
+                self._stopped_listening)
+
+            # Disconnect the old kernel manager's channels.
             sub = self._kernel_manager.sub_channel
             xreq = self._kernel_manager.xreq_channel
             sub.message_received.disconnect(self._handle_sub)
             xreq.execute_reply.disconnect(self._handle_execute_reply)
             xreq.complete_reply.disconnect(self._handle_complete_reply)
             xreq.object_info_reply.disconnect(self._handle_object_info_reply)
 
-        # Connect the new kernel manager.
+        # Set the new kernel manager.
         self._kernel_manager = kernel_manager
+        if kernel_manager is None:
+            return
+
+        # Connect the new kernel manager.
+        kernel_manager.started_listening.connect(self._started_listening)
+        kernel_manager.stopped_listening.connect(self._stopped_listening)
+
+        # Connect the new kernel manager's channels.
         sub = kernel_manager.sub_channel
         xreq = kernel_manager.xreq_channel
         sub.message_received.connect(self._handle_sub)
         xreq.execute_reply.connect(self._handle_execute_reply)
         xreq.complete_reply.connect(self._handle_complete_reply)
         xreq.object_info_reply.connect(self._handle_object_info_reply)
         
-        self._show_prompt('>>> ')
+        # Handle the case where the kernel manager started listening before
+        # we connected.
+        if kernel_manager.is_listening:
+            self._started_listening()
 
     kernel_manager = property(_get_kernel_manager, _set_kernel_manager)
 
     #---------------------------------------------------------------------------
     # 'FrontendWidget' protected interface
     #---------------------------------------------------------------------------
 
     def _call_tip(self):
         """ Shows a call tip, if appropriate, at the current cursor location.
         """
         # Decide if it makes sense to show a call tip
         cursor = self.textCursor()
         cursor.movePosition(QtGui.QTextCursor.Left)
         document = self.document()
         if document.characterAt(cursor.position()).toAscii() != '(':
             return False
         context = self._get_context(cursor)
         if not context:
             return False
 
         # Send the metadata request to the kernel
         name = '.'.join(context)
         self._calltip_id = self.kernel_manager.xreq_channel.object_info(name)
         self._calltip_pos = self.textCursor().position()
         return True
 
     def _complete(self):
         """ Performs completion at the current cursor location.
         """
         # Decide if it makes sense to do completion
         context = self._get_context()
         if not context:
             return False
 
         # Send the completion request to the kernel
         text = '.'.join(context)
         self._complete_id = self.kernel_manager.xreq_channel.complete(
             text, self.input_buffer_cursor_line, self.input_buffer)
         self._complete_pos = self.textCursor().position()
         return True
 
     def _get_context(self, cursor=None):
         """ Gets the context at the current cursor location.
         """
         if cursor is None:
             cursor = self.textCursor()
         cursor.movePosition(QtGui.QTextCursor.StartOfLine, 
                             QtGui.QTextCursor.KeepAnchor)
         text = unicode(cursor.selectedText())
         return self._completion_lexer.get_context(text)
 
     #------ Signal handlers ----------------------------------------------------
 
     def _document_contents_change(self, position, removed, added):
         """ Called whenever the document's content changes. Display a calltip
             if appropriate.
         """
         # Calculate where the cursor should be *after* the change:
         position += added
 
         document = self.document()
         if position == self.textCursor().position():
             self._call_tip()
 
     def _handle_sub(self, omsg):
         if not self._hidden:
             handler = getattr(self, '_handle_%s' % omsg['msg_type'], None)
             if handler is not None:
                 handler(omsg)
 
     def _handle_pyout(self, omsg):
         session = omsg['parent_header']['session']
         if session == self.kernel_manager.session.session:
             self.appendPlainText(omsg['content']['data'] + '\n')
 
     def _handle_stream(self, omsg):
         self.appendPlainText(omsg['content']['data'])
         
     def _handle_execute_reply(self, rep):
         # Make sure that all output from the SUB channel has been processed
         # before writing a new prompt.
         self.kernel_manager.sub_channel.flush()
 
         content = rep['content']
         status = content['status']
         if status == 'error':
             self.appendPlainText(content['traceback'][-1])
         elif status == 'aborted':
             text = "ERROR: ABORTED\n"
             self.appendPlainText(text)
         self._hidden = True
-        self._show_prompt('>>> ')
+        self._show_prompt()
         self.executed.emit(rep)
 
     def _handle_complete_reply(self, rep):
         cursor = self.textCursor()
         if rep['parent_header']['msg_id'] == self._complete_id and \
                 cursor.position() == self._complete_pos:
             text = '.'.join(self._get_context())
             cursor.movePosition(QtGui.QTextCursor.Left, n=len(text))
             self._complete_with_items(cursor, rep['content']['matches'])
 
     def _handle_object_info_reply(self, rep):
         cursor = self.textCursor()
         if rep['parent_header']['msg_id'] == self._calltip_id and \
                 cursor.position() == self._calltip_pos:
             doc = rep['content']['docstring']
             if doc:
                 self._call_tip_widget.show_tip(doc)
+
+    def _started_listening(self):
+        self.clear()
+
+    def _stopped_listening(self):
+        pass

IPython/frontend/qt/console/ipython_widget.py

@@ -1,95 +1,96 b''
 # System library imports
 from PyQt4 import QtCore, QtGui
 
 # Local imports
 from frontend_widget import FrontendWidget
 
 
 class IPythonWidget(FrontendWidget):
     """ A FrontendWidget for an IPython kernel.
     """
 
     #---------------------------------------------------------------------------
     # 'FrontendWidget' interface
     #---------------------------------------------------------------------------
     
-    def __init__(self, kernel_manager, parent=None):
-        super(IPythonWidget, self).__init__(kernel_manager, parent)
+    def __init__(self, parent=None):
+        super(IPythonWidget, self).__init__(parent)
 
         self._magic_overrides = {}
 
     def execute_source(self, source, hidden=False, interactive=False):
         """ Reimplemented to override magic commands.
         """
         magic_source = source.strip()
         if magic_source.startswith('%'):
             magic_source = magic_source[1:]
         magic, sep, arguments = magic_source.partition(' ')
         if not magic:
             magic = magic_source
 
         callback = self._magic_overrides.get(magic)
         if callback:
             output = callback(arguments)
             if output:
                 self.appendPlainText(output)
             self._show_prompt('>>> ')
             return True
         else:
             return super(IPythonWidget, self).execute_source(source, hidden,
                                                              interactive)
 
     #---------------------------------------------------------------------------
     # 'IPythonWidget' interface
     #---------------------------------------------------------------------------
 
     def set_magic_override(self, magic, callback):
         """ Overrides an IPython magic command. This magic will be intercepted
             by the frontend rather than passed on to the kernel and 'callback'
             will be called with a single argument: a string of argument(s) for
             the magic. The callback can (optionally) return text to print to the
             console.
         """
         self._magic_overrides[magic] = callback
 
     def remove_magic_override(self, magic):
         """ Removes the override for the specified magic, if there is one.
         """
         try:
             del self._magic_overrides[magic]
         except KeyError:
             pass
 
 
 if __name__ == '__main__':
     from IPython.external.argparse import ArgumentParser
     from IPython.frontend.qt.kernelmanager import QtKernelManager
 
     # Don't let Qt swallow KeyboardInterupts.
     import signal
     signal.signal(signal.SIGINT, signal.SIG_DFL)
 
     # Parse command line arguments.
     parser = ArgumentParser()
     parser.add_argument('--ip', type=str, default='127.0.0.1',
                         help='set the kernel\'s IP address [default localhost]')
     parser.add_argument('--xreq', type=int, metavar='PORT', default=5575,
                         help='set the XREQ Channel port [default %(default)i]')
     parser.add_argument('--sub', type=int, metavar='PORT', default=5576,
                         help='set the SUB Channel port [default %(default)i]')
     namespace = parser.parse_args()
 
     # Create KernelManager
     ip = namespace.ip
     kernel_manager = QtKernelManager(xreq_address = (ip, namespace.xreq),
                                      sub_address = (ip, namespace.sub))
     kernel_manager.start_listening()
 
     # Launch application
     app = QtGui.QApplication([])
-    widget = IPythonWidget(kernel_manager)
+    widget = IPythonWidget()
+    widget.kernel_manager = kernel_manager
     widget.setWindowTitle('Python')
     widget.resize(640, 480)
     widget.show()
     app.exec_()
     

IPython/frontend/qt/kernelmanager.py

@@ -1,118 +1,144 b''
-""" A KernelManager that provides channels that use signals and slots.
+""" Defines a KernelManager that provides signals and slots.
 """
 
 # System library imports.
 from PyQt4 import QtCore
 
 # IPython imports.
 from IPython.zmq.kernelmanager import KernelManager, SubSocketChannel, \
     XReqSocketChannel, RepSocketChannel
+from util import MetaQObjectHasTraits
 
 
 class QtSubSocketChannel(SubSocketChannel, QtCore.QObject):
 
     # Emitted when any message is received.
     message_received = QtCore.pyqtSignal(object)
 
     # Emitted when a message of type 'pyout' or 'stdout' is received.
     output_received = QtCore.pyqtSignal(object)
 
     # Emitted when a message of type 'pyerr' or 'stderr' is received.
     error_received = QtCore.pyqtSignal(object)
 
     #---------------------------------------------------------------------------
     # 'object' interface
     #---------------------------------------------------------------------------
     
     def __init__(self, *args, **kw):
         """ Reimplemented to ensure that QtCore.QObject is initialized first.
         """
         QtCore.QObject.__init__(self)
         SubSocketChannel.__init__(self, *args, **kw)
 
     #---------------------------------------------------------------------------
     # 'SubSocketChannel' interface
     #---------------------------------------------------------------------------
     
     def call_handlers(self, msg):
         """ Reimplemented to emit signals instead of making callbacks.
         """
         # Emit the generic signal.
         self.message_received.emit(msg)
         
         # Emit signals for specialized message types.
         msg_type = msg['msg_type']
         if msg_type in ('pyout', 'stdout'):
             self.output_received.emit(msg)
         elif msg_type in ('pyerr', 'stderr'):
             self.error_received.emit(msg)
 
     def flush(self):
         """ Reimplemented to ensure that signals are dispatched immediately.
         """
         super(QtSubSocketChannel, self).flush()
         QtCore.QCoreApplication.instance().processEvents()
 
 
 class QtXReqSocketChannel(XReqSocketChannel, QtCore.QObject):
 
     # Emitted when any message is received.
     message_received = QtCore.pyqtSignal(object)
 
     # Emitted when a reply has been received for the corresponding request type.
     execute_reply = QtCore.pyqtSignal(object)
     complete_reply = QtCore.pyqtSignal(object)
     object_info_reply = QtCore.pyqtSignal(object)
 
     #---------------------------------------------------------------------------
     # 'object' interface
     #---------------------------------------------------------------------------
     
     def __init__(self, *args, **kw):
         """ Reimplemented to ensure that QtCore.QObject is initialized first.
         """
         QtCore.QObject.__init__(self)
         XReqSocketChannel.__init__(self, *args, **kw)
     
     #---------------------------------------------------------------------------
     # 'XReqSocketChannel' interface
     #---------------------------------------------------------------------------
     
     def call_handlers(self, msg):
         """ Reimplemented to emit signals instead of making callbacks.
         """
         # Emit the generic signal.
         self.message_received.emit(msg)
         
         # Emit signals for specialized message types.
         msg_type = msg['msg_type']
         signal = getattr(self, msg_type, None)
         if signal:
             signal.emit(msg)
 
     def _queue_request(self, msg, callback):
         """ Reimplemented to skip callback handling.
         """
         self.command_queue.put(msg)
 
 
 class QtRepSocketChannel(RepSocketChannel, QtCore.QObject):
 
     #---------------------------------------------------------------------------
     # 'object' interface
     #---------------------------------------------------------------------------
     
     def __init__(self, *args, **kw):
         """ Reimplemented to ensure that QtCore.QObject is initialized first.
         """
         QtCore.QObject.__init__(self)
         RepSocketChannel.__init__(self, *args, **kw)
 
 
-class QtKernelManager(KernelManager):
-    """ A KernelManager that provides channels that use signals and slots.
+class QtKernelManager(KernelManager, QtCore.QObject):
+    """ A KernelManager that provides signals and slots.
     """
 
+    __metaclass__ = MetaQObjectHasTraits
+
+    # Emitted when the kernel manager has started listening.
+    started_listening = QtCore.pyqtSignal()
+
+    # Emitted when the kernel manager has stopped listening.
+    stopped_listening = QtCore.pyqtSignal()
+
+    # Use Qt-specific channel classes that emit signals.
     sub_channel_class = QtSubSocketChannel
     xreq_channel_class = QtXReqSocketChannel
     rep_channel_class = QtRepSocketChannel
+
+    #---------------------------------------------------------------------------
+    # 'KernelManager' interface
+    #---------------------------------------------------------------------------
+    
+    def start_listening(self):
+        """ Reimplemented to emit signal.
+        """
+        super(QtKernelManager, self).start_listening()
+        self.started_listening.emit()
+
+    def stop_listening(self):
+        """ Reimplemented to emit signal.
+        """ 
+        super(QtKernelManager, self).stop_listening()
+        self.stopped_listening.emit()