Fixed ANSI compliance issue in AnsiCodeProcessor.

Among other things, this fixes 'ls' on Mac OS. I also added a safety SGR reset in FrontendWidget to prevent bad ANSI codes from hosing the input buffer.

IPython/frontend/qt/console/ansi_code_processor.py

@@ -1,230 +1,233 b''
 """ Utilities for processing ANSI escape codes and special ASCII characters.
 """
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 # Standard library imports
 from collections import namedtuple
 import re
 
 # System library imports
 from PyQt4 import QtCore, QtGui
 
 #-----------------------------------------------------------------------------
 # Constants and datatypes
 #-----------------------------------------------------------------------------
 
 # An action for erase requests (ED and EL commands).
 EraseAction = namedtuple('EraseAction', ['action', 'area', 'erase_to'])
 
 # An action for cursor move requests (CUU, CUD, CUF, CUB, CNL, CPL, CHA, CUP,
 # and HVP commands).
 # FIXME: Not implemented in AnsiCodeProcessor.
 MoveAction = namedtuple('MoveAction', ['action', 'dir', 'unit', 'count'])
 
 # An action for scroll requests (SU and ST) and form feeds.
 ScrollAction = namedtuple('ScrollAction', ['action', 'dir', 'unit', 'count'])
 
 #-----------------------------------------------------------------------------
 # Classes
 #-----------------------------------------------------------------------------
 
 class AnsiCodeProcessor(object):
     """ Translates special ASCII characters and ANSI escape codes into readable
         attributes.
     """
 
     # Whether to increase intensity or set boldness for SGR code 1.
     # (Different terminals handle this in different ways.)
     bold_text_enabled = False    
 
     # Protected class variables.
     _ansi_commands = 'ABCDEFGHJKSTfmnsu'
     _ansi_pattern = re.compile('\x01?\x1b\[(.*?)([%s])\x02?' % _ansi_commands)
     _special_pattern = re.compile('([\f])')
 
     #---------------------------------------------------------------------------
     # AnsiCodeProcessor interface
     #---------------------------------------------------------------------------
 
     def __init__(self):
         self.actions = []
         self.reset_sgr()
 
     def reset_sgr(self):
         """ Reset graphics 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
 
     def split_string(self, string):
         """ Yields substrings for which the same escape code applies.
         """
         self.actions = []
         start = 0
 
         for match in self._ansi_pattern.finditer(string):
             raw = string[start:match.start()]
             substring = self._special_pattern.sub(self._replace_special, raw)
             if substring or self.actions:
                 yield substring
             start = match.end()
 
             self.actions = []
             try:
                 params = []
                 for param in match.group(1).split(';'):
                     if param:
                         params.append(int(param))
             except ValueError:
                 # Silently discard badly formed escape codes.
                 pass
             else:
                 self.set_csi_code(match.group(2), params)
 
         raw = string[start:]
         substring = self._special_pattern.sub(self._replace_special, raw)
         if substring or self.actions:
             yield substring
 
     def set_csi_code(self, command, params=[]):
         """ Set attributes based on CSI (Control Sequence Introducer) code.
 
         Parameters
         ----------
         command : str
             The code identifier, i.e. the final character in the sequence.
         
         params : sequence of integers, optional
             The parameter codes for the command.
         """
         if command == 'm':   # SGR - Select Graphic Rendition
-            for code in params:
-                self.set_sgr_code(code)
+            if params:
+                for code in params:
+                    self.set_sgr_code(code)
+            else:
+                self.set_sgr_code(0)
 
         elif (command == 'J' or # ED - Erase Data
               command == 'K'):  # EL - Erase in Line
             code = params[0] if params else 0
             if 0 <= code <= 2:
                 area = 'screen' if command == 'J' else 'line'
                 if code == 0:
                     erase_to = 'end'
                 elif code == 1:
                     erase_to = 'start'
                 elif code == 2:
                     erase_to = 'all'
                 self.actions.append(EraseAction('erase', area, erase_to))
 
         elif (command == 'S' or # SU - Scroll Up
               command == 'T'):  # SD - Scroll Down
             dir = 'up' if command == 'S' else 'down'
             count = params[0] if params else 1
             self.actions.append(ScrollAction('scroll', dir, 'line', count))
         
     def set_sgr_code(self, code):
         """ Set attributes based on SGR (Select Graphic Rendition) code.
         """
         if code == 0:
             self.reset_sgr()
         elif code == 1:
             if self.bold_text_enabled:
                 self.bold = True
             else:
                 self.intensity = 1
         elif code == 2:
             self.intensity = 0
         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
 
     #---------------------------------------------------------------------------
     # Protected interface
     #---------------------------------------------------------------------------
 
     def _replace_special(self, match):
         special = match.group(1)
         if special == '\f':
             self.actions.append(ScrollAction('scroll', 'down', 'page', 1))
         return ''
         
 
 class QtAnsiCodeProcessor(AnsiCodeProcessor):
     """ Translates ANSI escape codes into QTextCharFormats.
     """
 
     # A map from color codes to RGB colors.
     default_map = (# Normal,      Bright/Light    ANSI color code
                    ('black',      'grey'),        # 0: black
                    ('darkred',    'red'),         # 1: red
                    ('darkgreen',  'lime'),        # 2: green
                    ('brown',      'yellow'),      # 3: yellow
                    ('darkblue',   'deepskyblue'), # 4: blue
                    ('darkviolet', 'magenta'),     # 5: magenta
                    ('steelblue',  'cyan'),        # 6: cyan
                    ('grey',       'white'))       # 7: white
 
     def __init__(self):
         super(QtAnsiCodeProcessor, self).__init__()
         self.color_map = self.default_map
     
     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.color_map[self.foreground_color][self.intensity]
             format.setForeground(QtGui.QColor(color))
 
         # Set background color
         if self.background_color is not None:
             color = self.color_map[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
 
     def set_background_color(self, color):
         """ Given a background color (a QColor), attempt to set a color map
             that will be aesthetically pleasing.
         """
         if color.value() < 127:
             # Colors appropriate for a terminal with a dark background.
             self.color_map = self.default_map
 
         else:
             # Colors appropriate for a terminal with a light background. For 
             # now, only use non-bright colors...
             self.color_map = [ (pair[0], pair[0]) for pair in self.default_map ]
 
             # ...and replace white with black.
             self.color_map[7] = ('black', 'black')

IPython/frontend/qt/console/frontend_widget.py

@@ -1,524 +1,530 b''
 # Standard library imports
 from collections import namedtuple
 import signal
 import sys
 
 # System library imports
 from pygments.lexers import PythonLexer
 from PyQt4 import QtCore, QtGui
 
 # Local imports
 from IPython.core.inputsplitter import InputSplitter, transform_classic_prompt
 from IPython.frontend.qt.base_frontend_mixin import BaseFrontendMixin
 from IPython.utils.io import raw_print
 from IPython.utils.traitlets import Bool
 from bracket_matcher import BracketMatcher
 from call_tip_widget import CallTipWidget
 from completion_lexer import CompletionLexer
 from history_console_widget import HistoryConsoleWidget
 from pygments_highlighter import PygmentsHighlighter
 
 
 class FrontendHighlighter(PygmentsHighlighter):
     """ A PygmentsHighlighter that can be turned on and off and that ignores
         prompts.
     """
 
     def __init__(self, frontend):
         super(FrontendHighlighter, self).__init__(frontend._control.document())
         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 not self.highlighting_on:
             return
 
         # The input to this function is unicode string that may contain
         # paragraph break characters, non-breaking spaces, etc. Here we acquire
         # the string as plain text so we can compare it.
         current_block = self.currentBlock()
         string = self._frontend._get_block_plain_text(current_block)
 
         # Decide whether to check for the regular or continuation prompt.
         if current_block.contains(self._frontend._prompt_pos):
             prompt = self._frontend._prompt
         else:
             prompt = self._frontend._continuation_prompt
 
         # Don't highlight the part of the string that contains the prompt.
         if string.startswith(prompt):
             self._current_offset = len(prompt)
             qstring.remove(0, len(prompt))
         else:
             self._current_offset = 0
 
         PygmentsHighlighter.highlightBlock(self, qstring)
 
     def rehighlightBlock(self, block):
         """ Reimplemented to temporarily enable highlighting if disabled.
         """
         old = self.highlighting_on
         self.highlighting_on = True
         super(FrontendHighlighter, self).rehighlightBlock(block)
         self.highlighting_on = old
 
     def setFormat(self, start, count, format):
         """ Reimplemented to highlight selectively.
         """
         start += self._current_offset
         PygmentsHighlighter.setFormat(self, start, count, format)
 
 
 class FrontendWidget(HistoryConsoleWidget, BaseFrontendMixin):
     """ A Qt frontend for a generic Python kernel.
     """
 
     # An option and corresponding signal for overriding the default kernel
     # interrupt behavior.
     custom_interrupt = Bool(False)
     custom_interrupt_requested = QtCore.pyqtSignal()
 
     # An option and corresponding signals for overriding the default kernel
     # restart behavior.
     custom_restart = Bool(False)
     custom_restart_kernel_died = QtCore.pyqtSignal(float)
     custom_restart_requested = QtCore.pyqtSignal()
    
     # Emitted when an 'execute_reply' has been received from the kernel and
     # processed by the FrontendWidget.
     executed = QtCore.pyqtSignal(object)
 
     # Emitted when an exit request has been received from the kernel.
     exit_requested = QtCore.pyqtSignal()
     
     # Protected class variables.
     _CallTipRequest = namedtuple('_CallTipRequest', ['id', 'pos'])
     _CompletionRequest = namedtuple('_CompletionRequest', ['id', 'pos'])
     _ExecutionRequest = namedtuple('_ExecutionRequest', ['id', 'kind'])
     _input_splitter_class = InputSplitter
 
     #---------------------------------------------------------------------------
     # 'object' interface
     #---------------------------------------------------------------------------
     
     def __init__(self, *args, **kw):
         super(FrontendWidget, self).__init__(*args, **kw)
 
         # FrontendWidget protected variables.
         self._bracket_matcher = BracketMatcher(self._control)
         self._call_tip_widget = CallTipWidget(self._control)
         self._completion_lexer = CompletionLexer(PythonLexer())
         self._copy_raw_action = QtGui.QAction('Copy (Raw Text)', None)
         self._hidden = False
         self._highlighter = FrontendHighlighter(self)
         self._input_splitter = self._input_splitter_class(input_mode='block')
         self._kernel_manager = None
         self._possible_kernel_restart = False
         self._request_info = {}
 
         # Configure the ConsoleWidget.
         self.tab_width = 4
         self._set_continuation_prompt('... ')
 
         # Configure actions.
         action = self._copy_raw_action
         key = QtCore.Qt.CTRL | QtCore.Qt.SHIFT | QtCore.Qt.Key_C
         action.setEnabled(False)
         action.setShortcut(QtGui.QKeySequence(key))
         action.setShortcutContext(QtCore.Qt.WidgetWithChildrenShortcut)
         action.triggered.connect(self.copy_raw)
         self.copy_available.connect(action.setEnabled)
         self.addAction(action)
 
         # Connect signal handlers.
         document = self._control.document()
         document.contentsChange.connect(self._document_contents_change)
 
     #---------------------------------------------------------------------------
     # 'ConsoleWidget' public interface
     #---------------------------------------------------------------------------
 
     def copy(self):
         """ Copy the currently selected text to the clipboard, removing prompts.
         """
         text = str(self._control.textCursor().selection().toPlainText())
         if text:
             # Remove prompts.
             lines = map(transform_classic_prompt, text.splitlines())
             text = '\n'.join(lines)
             # Expand tabs so that we respect PEP-8.
             QtGui.QApplication.clipboard().setText(text.expandtabs(4))
 
     #---------------------------------------------------------------------------
     # 'ConsoleWidget' abstract interface
     #---------------------------------------------------------------------------
 
     def _is_complete(self, source, interactive):
         """ Returns whether 'source' can be completely processed and a new
             prompt created. When triggered by an Enter/Return key press,
             'interactive' is True; otherwise, it is False.
         """
         complete = self._input_splitter.push(source.expandtabs(4))
         if interactive:
             complete = not self._input_splitter.push_accepts_more()
         return complete
 
     def _execute(self, source, hidden):
         """ Execute 'source'. If 'hidden', do not show any output.
 
         See parent class :meth:`execute` docstring for full details.
         """
         msg_id = self.kernel_manager.xreq_channel.execute(source, hidden)
         self._request_info['execute'] = self._ExecutionRequest(msg_id, 'user')
         self._hidden = hidden
         
     def _prompt_started_hook(self):
         """ Called immediately after a new prompt is displayed.
         """
         if not self._reading:
             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.
         """
         if not self._reading:
             self._highlighter.highlighting_on = False
 
     def _tab_pressed(self):
         """ Called when the tab key is pressed. Returns whether to continue
             processing the event.
         """
         # Perform tab completion if:
         # 1) The cursor is in the input buffer.
         # 2) There is a non-whitespace character before the cursor.
         text = self._get_input_buffer_cursor_line()
         if text is None:
             return False
         complete = bool(text[:self._get_input_buffer_cursor_column()].strip())
         if complete:
             self._complete()
         return not complete
 
     #---------------------------------------------------------------------------
     # 'ConsoleWidget' protected interface
     #---------------------------------------------------------------------------
 
     def _context_menu_make(self, pos):
         """ Reimplemented to add an action for raw copy.
         """
         menu = super(FrontendWidget, self)._context_menu_make(pos)
         for before_action in menu.actions():
             if before_action.shortcut().matches(QtGui.QKeySequence.Paste) == \
                     QtGui.QKeySequence.ExactMatch:
                 menu.insertAction(before_action, self._copy_raw_action)
                 break
         return menu
 
     def _event_filter_console_keypress(self, event):
         """ Reimplemented to allow execution interruption.
         """
         key = event.key()
         if self._control_key_down(event.modifiers(), include_command=False):
             if key == QtCore.Qt.Key_C and self._executing:
                 self.interrupt_kernel()
                 return True
             elif key == QtCore.Qt.Key_Period:
                 message = 'Are you sure you want to restart the kernel?'
                 self.restart_kernel(message, instant_death=False)
                 return True
         return super(FrontendWidget, self)._event_filter_console_keypress(event)
 
     def _insert_continuation_prompt(self, cursor):
         """ Reimplemented for auto-indentation.
         """
         super(FrontendWidget, self)._insert_continuation_prompt(cursor)
         spaces = self._input_splitter.indent_spaces
         cursor.insertText('\t' * (spaces / self.tab_width))
         cursor.insertText(' ' * (spaces % self.tab_width))
 
     #---------------------------------------------------------------------------
     # 'BaseFrontendMixin' abstract interface
     #---------------------------------------------------------------------------
 
     def _handle_complete_reply(self, rep):
         """ Handle replies for tab completion.
         """
         cursor = self._get_cursor()
         info = self._request_info.get('complete')
         if info and info.id == rep['parent_header']['msg_id'] and \
                 info.pos == cursor.position():
             text = '.'.join(self._get_context())
             cursor.movePosition(QtGui.QTextCursor.Left, n=len(text))
             self._complete_with_items(cursor, rep['content']['matches'])
 
     def _handle_execute_reply(self, msg):
         """ Handles replies for code execution.
         """
         info = self._request_info.get('execute')
         if info and info.id == msg['parent_header']['msg_id'] and \
                 info.kind == 'user' and not self._hidden:
             # Make sure that all output from the SUB channel has been processed
             # before writing a new prompt.
             self.kernel_manager.sub_channel.flush()
 
+            # Reset the ANSI style information to prevent bad text in stdout
+            # from messing up our colors. We're not a true terminal so we're
+            # allowed to do this.
+            if self.ansi_codes:
+                self._ansi_processor.reset_sgr()
+
             content = msg['content']
             status = content['status']
             if status == 'ok':
                 self._process_execute_ok(msg)
             elif status == 'error':
                 self._process_execute_error(msg)
             elif status == 'abort':
                 self._process_execute_abort(msg)
 
             self._show_interpreter_prompt_for_reply(msg)
             self.executed.emit(msg)
 
     def _handle_input_request(self, msg):
         """ Handle requests for raw_input.
         """
         if self._hidden:
             raise RuntimeError('Request for raw input during hidden execution.')
 
         # Make sure that all output from the SUB channel has been processed
         # before entering readline mode.
         self.kernel_manager.sub_channel.flush()
 
         def callback(line):
             self.kernel_manager.rep_channel.input(line)
         self._readline(msg['content']['prompt'], callback=callback)
 
     def _handle_kernel_died(self, since_last_heartbeat):
         """ Handle the kernel's death by asking if the user wants to restart.
         """
         message = 'The kernel heartbeat has been inactive for %.2f ' \
                   'seconds. Do you want to restart the kernel? You may ' \
                   'first want to check the network connection.' % \
                   since_last_heartbeat
         if self.custom_restart:
             self.custom_restart_kernel_died.emit(since_last_heartbeat)
         else:
             self.restart_kernel(message, instant_death=True)
 
     def _handle_object_info_reply(self, rep):
         """ Handle replies for call tips.
         """
         cursor = self._get_cursor()
         info = self._request_info.get('call_tip')
         if info and info.id == rep['parent_header']['msg_id'] and \
                 info.pos == cursor.position():
             doc = rep['content']['docstring']
             if doc:
                 self._call_tip_widget.show_docstring(doc)
 
     def _handle_pyout(self, msg):
         """ Handle display hook output.
         """
         if not self._hidden and self._is_from_this_session(msg):
             self._append_plain_text(msg['content']['data'] + '\n')
 
     def _handle_stream(self, msg):
         """ Handle stdout, stderr, and stdin.
         """
         if not self._hidden and self._is_from_this_session(msg):
             # Most consoles treat tabs as being 8 space characters. Convert tabs
             # to spaces so that output looks as expected regardless of this
             # widget's tab width.
             text = msg['content']['data'].expandtabs(8)
             
             self._append_plain_text(text)
             self._control.moveCursor(QtGui.QTextCursor.End)
     
     def _started_channels(self):
         """ Called when the KernelManager channels have started listening or 
             when the frontend is assigned an already listening KernelManager.
         """
         self._control.clear()
         self._append_plain_text(self._get_banner())
         self._show_interpreter_prompt()
 
     def _stopped_channels(self):
         """ Called when the KernelManager channels have stopped listening or
             when a listening KernelManager is removed from the frontend.
         """
         self._executing = self._reading = False
         self._highlighter.highlighting_on = False
 
     #---------------------------------------------------------------------------
     # 'FrontendWidget' public interface
     #---------------------------------------------------------------------------
 
     def copy_raw(self):
         """ Copy the currently selected text to the clipboard without attempting
             to remove prompts or otherwise alter the text.
         """
         self._control.copy()
 
     def execute_file(self, path, hidden=False):
         """ Attempts to execute file with 'path'. If 'hidden', no output is
             shown.
         """
         self.execute('execfile("%s")' % path, hidden=hidden)
 
     def interrupt_kernel(self):
         """ Attempts to interrupt the running kernel.
         """
         if self.custom_interrupt:
             self.custom_interrupt_requested.emit()
         elif self.kernel_manager.has_kernel:
             self.kernel_manager.signal_kernel(signal.SIGINT)
         else:
             self._append_plain_text('Kernel process is either remote or '
                                     'unspecified. Cannot interrupt.\n')
 
     def restart_kernel(self, message, instant_death=False):
         """ Attempts to restart the running kernel.
         """
         # FIXME: instant_death should be configurable via a checkbox in the
         # dialog.  Right now at least the heartbeat path sets it to True and
         # the manual restart to False.  But those should just be the
         # pre-selected states of a checkbox that the user could override if so
         # desired.  But I don't know enough Qt to go implementing the checkbox
         # now.
 
         # We want to make sure that if this dialog is already happening, that
         # other signals don't trigger it again. This can happen when the 
         # kernel_died heartbeat signal is emitted and the user is slow to
         # respond to the dialog.
         if not self._possible_kernel_restart:
             if self.custom_restart:
                 self.custom_restart_requested.emit()
             elif self.kernel_manager.has_kernel:
                 # Setting this to True will prevent this logic from happening
                 # again until the current pass is completed.
                 self._possible_kernel_restart = True
                 buttons = QtGui.QMessageBox.Yes | QtGui.QMessageBox.No
                 result = QtGui.QMessageBox.question(self, 'Restart kernel?',
                                                     message, buttons)
                 if result == QtGui.QMessageBox.Yes:
                     try:
                         self.kernel_manager.restart_kernel(
                             instant_death=instant_death)
                     except RuntimeError:
                         message = 'Kernel started externally. Cannot restart.\n'
                         self._append_plain_text(message)
                     else:
                         self._stopped_channels()
                         self._append_plain_text('Kernel restarting...\n')
                         self._show_interpreter_prompt()
                 # This might need to be moved to another location?
                 self._possible_kernel_restart = False
             else:
                 self._append_plain_text('Kernel process is either remote or '
                                         'unspecified. Cannot restart.\n')
 
     #---------------------------------------------------------------------------
     # '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._get_cursor()
         cursor.movePosition(QtGui.QTextCursor.Left)
         if cursor.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)
         msg_id = self.kernel_manager.xreq_channel.object_info(name)
         pos = self._get_cursor().position()
         self._request_info['call_tip'] = self._CallTipRequest(msg_id, pos)
         return True
 
     def _complete(self):
         """ Performs completion at the current cursor location.
         """
         context = self._get_context()
         if context:
             # Send the completion request to the kernel
             msg_id = self.kernel_manager.xreq_channel.complete(
                 '.'.join(context),                       # text
                 self._get_input_buffer_cursor_line(),    # line
                 self._get_input_buffer_cursor_column(),  # cursor_pos
                 self.input_buffer)                       # block 
             pos = self._get_cursor().position()
             info = self._CompletionRequest(msg_id, pos)
             self._request_info['complete'] = info
 
     def _get_banner(self):
         """ Gets a banner to display at the beginning of a session.
         """
         banner = 'Python %s on %s\nType "help", "copyright", "credits" or ' \
             '"license" for more information.'
         return banner % (sys.version, sys.platform)
 
     def _get_context(self, cursor=None):
         """ Gets the context for the specified cursor (or the current cursor
             if none is specified).
         """
         if cursor is None:
             cursor = self._get_cursor()
         cursor.movePosition(QtGui.QTextCursor.StartOfBlock, 
                             QtGui.QTextCursor.KeepAnchor)
         text = str(cursor.selection().toPlainText())
         return self._completion_lexer.get_context(text)
 
     def _process_execute_abort(self, msg):
         """ Process a reply for an aborted execution request.
         """
         self._append_plain_text("ERROR: execution aborted\n")
 
     def _process_execute_error(self, msg):
         """ Process a reply for an execution request that resulted in an error.
         """
         content = msg['content']
         traceback = ''.join(content['traceback'])
         self._append_plain_text(traceback)
 
     def _process_execute_ok(self, msg):
         """ Process a reply for a successful execution equest.
         """
         payload = msg['content']['payload']
         for item in payload:
             if not self._process_execute_payload(item):
                 warning = 'Warning: received unknown payload of type %s'
                 raw_print(warning % repr(item['source']))
 
     def _process_execute_payload(self, item):
         """ Process a single payload item from the list of payload items in an
             execution reply. Returns whether the payload was handled.
         """
         # The basic FrontendWidget doesn't handle payloads, as they are a
         # mechanism for going beyond the standard Python interpreter model.
         return False
 
     def _show_interpreter_prompt(self):
         """ Shows a prompt for the interpreter.
         """
         self._show_prompt('>>> ')
 
     def _show_interpreter_prompt_for_reply(self, msg):
         """ Shows a prompt for the interpreter given an 'execute_reply' message.
         """
         self._show_interpreter_prompt()
 
     #------ Signal handlers ----------------------------------------------------
 
     def _document_contents_change(self, position, removed, added):
         """ Called whenever the document's content changes. Display a call tip
             if appropriate.
         """
         # Calculate where the cursor should be *after* the change:
         position += added
 
         document = self._control.document()
         if position == self._get_cursor().position():
             self._call_tip()