protect Widget._style_sheet_changed from being called before _control exists

also ensure _control attributes start out as None, rather than undefined

IPython/frontend/qt/console/console_widget.py

@@ -1,1852 +1,1855 b''
 """ An abstract base class for console-type widgets.
 """
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 # Standard library imports
 import os
 from os.path import commonprefix
 import re
 import sys
 from textwrap import dedent
 from unicodedata import category
 
 # System library imports
 from IPython.external.qt import QtCore, QtGui
 
 # Local imports
 from IPython.config.configurable import LoggingConfigurable
 from IPython.frontend.qt.rich_text import HtmlExporter
 from IPython.frontend.qt.util import MetaQObjectHasTraits, get_font
 from IPython.utils.text import columnize
 from IPython.utils.traitlets import Bool, Enum, Integer, Unicode
 from ansi_code_processor import QtAnsiCodeProcessor
 from completion_widget import CompletionWidget
 from kill_ring import QtKillRing
 
 #-----------------------------------------------------------------------------
 # Functions
 #-----------------------------------------------------------------------------
 
 def is_letter_or_number(char):
     """ Returns whether the specified unicode character is a letter or a number.
     """
     cat = category(char)
     return cat.startswith('L') or cat.startswith('N')
 
 #-----------------------------------------------------------------------------
 # Classes
 #-----------------------------------------------------------------------------
 
 class ConsoleWidget(LoggingConfigurable, QtGui.QWidget):
     """ An abstract base class for console-type widgets. This class has
         functionality for:
 
             * Maintaining a prompt and editing region
             * Providing the traditional Unix-style console keyboard shortcuts
             * Performing tab completion
             * Paging text
             * Handling ANSI escape codes
 
         ConsoleWidget also provides a number of utility methods that will be
         convenient to implementors of a console-style widget.
     """
     __metaclass__ = MetaQObjectHasTraits
 
     #------ Configuration ------------------------------------------------------
 
     ansi_codes = Bool(True, config=True,
         help="Whether to process ANSI escape codes."
     )
     buffer_size = Integer(500, config=True,
         help="""
         The maximum number of lines of text before truncation. Specifying a
         non-positive number disables text truncation (not recommended).
         """
     )
     gui_completion = Bool(False, config=True,
         help="""
         Use a list widget instead of plain text output for tab completion.
         """
     )
     # NOTE: this value can only be specified during initialization.
     kind = Enum(['plain', 'rich'], default_value='plain', config=True,
         help="""
         The type of underlying text widget to use. Valid values are 'plain',
         which specifies a QPlainTextEdit, and 'rich', which specifies a
         QTextEdit.
         """
     )
     # NOTE: this value can only be specified during initialization.
     paging = Enum(['inside', 'hsplit', 'vsplit', 'custom', 'none'],
                   default_value='inside', config=True,
         help="""
         The type of paging to use. Valid values are:
 
             'inside' : The widget pages like a traditional terminal.
             'hsplit' : When paging is requested, the widget is split
                        horizontally. The top pane contains the console, and the
                        bottom pane contains the paged text.
             'vsplit' : Similar to 'hsplit', except that a vertical splitter
                        used.
             'custom' : No action is taken by the widget beyond emitting a
                        'custom_page_requested(str)' signal.
             'none'   : The text is written directly to the console.
         """)
 
     font_family = Unicode(config=True,
         help="""The font family to use for the console.
         On OSX this defaults to Monaco, on Windows the default is
         Consolas with fallback of Courier, and on other platforms
         the default is Monospace.
         """)
     def _font_family_default(self):
         if sys.platform == 'win32':
             # Consolas ships with Vista/Win7, fallback to Courier if needed
             return 'Consolas'
         elif sys.platform == 'darwin':
             # OSX always has Monaco, no need for a fallback
             return 'Monaco'
         else:
             # Monospace should always exist, no need for a fallback
             return 'Monospace'
 
     font_size = Integer(config=True,
         help="""The font size. If unconfigured, Qt will be entrusted
         with the size of the font.
         """)
 
     # Whether to override ShortcutEvents for the keybindings defined by this
     # widget (Ctrl+n, Ctrl+a, etc). Enable this if you want this widget to take
     # priority (when it has focus) over, e.g., window-level menu shortcuts.
     override_shortcuts = Bool(False)
 
     #------ Signals ------------------------------------------------------------
 
     # Signals that indicate ConsoleWidget state.
     copy_available = QtCore.Signal(bool)
     redo_available = QtCore.Signal(bool)
     undo_available = QtCore.Signal(bool)
 
     # Signal emitted when paging is needed and the paging style has been
     # specified as 'custom'.
     custom_page_requested = QtCore.Signal(object)
 
     # Signal emitted when the font is changed.
     font_changed = QtCore.Signal(QtGui.QFont)
 
     #------ Protected class variables ------------------------------------------
 
+    # control handles
+    _control = None
+    _page_control = None
+    _splitter = None
+    
     # When the control key is down, these keys are mapped.
     _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_P : QtCore.Qt.Key_Up,
                          QtCore.Qt.Key_N : QtCore.Qt.Key_Down,
                          QtCore.Qt.Key_H : QtCore.Qt.Key_Backspace, }
     if not sys.platform == 'darwin':
         # On OS X, Ctrl-E already does the right thing, whereas End moves the
         # cursor to the bottom of the buffer.
         _ctrl_down_remap[QtCore.Qt.Key_E] = QtCore.Qt.Key_End
 
     # The shortcuts defined by this widget. We need to keep track of these to
     # support 'override_shortcuts' above.
     _shortcuts = set(_ctrl_down_remap.keys() +
                      [ QtCore.Qt.Key_C, QtCore.Qt.Key_G, QtCore.Qt.Key_O,
                        QtCore.Qt.Key_V ])
 
     #---------------------------------------------------------------------------
     # 'QObject' interface
     #---------------------------------------------------------------------------
 
     def __init__(self, parent=None, **kw):
         """ Create a ConsoleWidget.
 
         Parameters:
         -----------
         parent : QWidget, optional [default None]
             The parent for this widget.
         """
         QtGui.QWidget.__init__(self, parent)
         LoggingConfigurable.__init__(self, **kw)
 
         # While scrolling the pager on Mac OS X, it tears badly.  The
         # NativeGesture is platform and perhaps build-specific hence
         # we take adequate precautions here.
         self._pager_scroll_events = [QtCore.QEvent.Wheel]
         if hasattr(QtCore.QEvent, 'NativeGesture'):
             self._pager_scroll_events.append(QtCore.QEvent.NativeGesture)
 
         # Create the layout and underlying text widget.
         layout = QtGui.QStackedLayout(self)
         layout.setContentsMargins(0, 0, 0, 0)
         self._control = self._create_control()
-        self._page_control = None
-        self._splitter = None
         if self.paging in ('hsplit', 'vsplit'):
             self._splitter = QtGui.QSplitter()
             if self.paging == 'hsplit':
                 self._splitter.setOrientation(QtCore.Qt.Horizontal)
             else:
                 self._splitter.setOrientation(QtCore.Qt.Vertical)
             self._splitter.addWidget(self._control)
             layout.addWidget(self._splitter)
         else:
             layout.addWidget(self._control)
 
         # Create the paging widget, if necessary.
         if self.paging in ('inside', 'hsplit', 'vsplit'):
             self._page_control = self._create_page_control()
             if self._splitter:
                 self._page_control.hide()
                 self._splitter.addWidget(self._page_control)
             else:
                 layout.addWidget(self._page_control)
 
         # Initialize protected variables. Some variables contain useful state
         # information for subclasses; they should be considered read-only.
         self._append_before_prompt_pos = 0
         self._ansi_processor = QtAnsiCodeProcessor()
         self._completion_widget = CompletionWidget(self._control)
         self._continuation_prompt = '> '
         self._continuation_prompt_html = None
         self._executing = False
         self._filter_drag = False
         self._filter_resize = False
         self._html_exporter = HtmlExporter(self._control)
         self._input_buffer_executing = ''
         self._input_buffer_pending = ''
         self._kill_ring = QtKillRing(self._control)
         self._prompt = ''
         self._prompt_html = None
         self._prompt_pos = 0
         self._prompt_sep = ''
         self._reading = False
         self._reading_callback = None
         self._tab_width = 8
         self._text_completing_pos = 0
 
         # Set a monospaced font.
         self.reset_font()
 
         # Configure actions.
         action = QtGui.QAction('Print', None)
         action.setEnabled(True)
         printkey = QtGui.QKeySequence(QtGui.QKeySequence.Print)
         if printkey.matches("Ctrl+P") and sys.platform != 'darwin':
             # Only override the default if there is a collision.
             # Qt ctrl = cmd on OSX, so the match gets a false positive on OSX.
             printkey = "Ctrl+Shift+P"
         action.setShortcut(printkey)
         action.setShortcutContext(QtCore.Qt.WidgetWithChildrenShortcut)
         action.triggered.connect(self.print_)
         self.addAction(action)
         self.print_action = action
 
         action = QtGui.QAction('Save as HTML/XML', None)
         action.setShortcut(QtGui.QKeySequence.Save)
         action.setShortcutContext(QtCore.Qt.WidgetWithChildrenShortcut)
         action.triggered.connect(self.export_html)
         self.addAction(action)
         self.export_action = action
 
         action = QtGui.QAction('Select All', None)
         action.setEnabled(True)
         selectall = QtGui.QKeySequence(QtGui.QKeySequence.SelectAll)
         if selectall.matches("Ctrl+A") and sys.platform != 'darwin':
             # Only override the default if there is a collision.
             # Qt ctrl = cmd on OSX, so the match gets a false positive on OSX.
             selectall = "Ctrl+Shift+A"
         action.setShortcut(selectall)
         action.setShortcutContext(QtCore.Qt.WidgetWithChildrenShortcut)
         action.triggered.connect(self.select_all)
         self.addAction(action)
         self.select_all_action = action
 
         self.increase_font_size = QtGui.QAction("Bigger Font",
                 self,
                 shortcut=QtGui.QKeySequence.ZoomIn,
                 shortcutContext=QtCore.Qt.WidgetWithChildrenShortcut,
                 statusTip="Increase the font size by one point",
                 triggered=self._increase_font_size)
         self.addAction(self.increase_font_size)
 
         self.decrease_font_size = QtGui.QAction("Smaller Font",
                 self,
                 shortcut=QtGui.QKeySequence.ZoomOut,
                 shortcutContext=QtCore.Qt.WidgetWithChildrenShortcut,
                 statusTip="Decrease the font size by one point",
                 triggered=self._decrease_font_size)
         self.addAction(self.decrease_font_size)
 
         self.reset_font_size = QtGui.QAction("Normal Font",
                 self,
                 shortcut="Ctrl+0",
                 shortcutContext=QtCore.Qt.WidgetWithChildrenShortcut,
                 statusTip="Restore the Normal font size",
                 triggered=self.reset_font)
         self.addAction(self.reset_font_size)
 
 
 
     def eventFilter(self, obj, event):
         """ Reimplemented to ensure a console-like behavior in the underlying
             text widgets.
         """
         etype = event.type()
         if etype == QtCore.QEvent.KeyPress:
 
             # Re-map keys for all filtered widgets.
             key = event.key()
             if self._control_key_down(event.modifiers()) and \
                     key in self._ctrl_down_remap:
                 new_event = QtGui.QKeyEvent(QtCore.QEvent.KeyPress,
                                             self._ctrl_down_remap[key],
                                             QtCore.Qt.NoModifier)
                 QtGui.qApp.sendEvent(obj, new_event)
                 return True
 
             elif obj == self._control:
                 return self._event_filter_console_keypress(event)
 
             elif obj == self._page_control:
                 return self._event_filter_page_keypress(event)
 
         # Make middle-click paste safe.
         elif etype == QtCore.QEvent.MouseButtonRelease and \
                 event.button() == QtCore.Qt.MidButton and \
                 obj == self._control.viewport():
             cursor = self._control.cursorForPosition(event.pos())
             self._control.setTextCursor(cursor)
             self.paste(QtGui.QClipboard.Selection)
             return True
 
         # Manually adjust the scrollbars *after* a resize event is dispatched.
         elif etype == QtCore.QEvent.Resize and not self._filter_resize:
             self._filter_resize = True
             QtGui.qApp.sendEvent(obj, event)
             self._adjust_scrollbars()
             self._filter_resize = False
             return True
 
         # Override shortcuts for all filtered widgets.
         elif etype == QtCore.QEvent.ShortcutOverride and \
                 self.override_shortcuts and \
                 self._control_key_down(event.modifiers()) and \
                 event.key() in self._shortcuts:
             event.accept()
 
         # Ensure that drags are safe. The problem is that the drag starting
         # logic, which determines whether the drag is a Copy or Move, is locked
         # down in QTextControl. If the widget is editable, which it must be if
         # we're not executing, the drag will be a Move. The following hack
         # prevents QTextControl from deleting the text by clearing the selection
         # when a drag leave event originating from this widget is dispatched.
         # The fact that we have to clear the user's selection is unfortunate,
         # but the alternative--trying to prevent Qt from using its hardwired
         # drag logic and writing our own--is worse.
         elif etype == QtCore.QEvent.DragEnter and \
                 obj == self._control.viewport() and \
                 event.source() == self._control.viewport():
             self._filter_drag = True
         elif etype == QtCore.QEvent.DragLeave and \
                 obj == self._control.viewport() and \
                 self._filter_drag:
             cursor = self._control.textCursor()
             cursor.clearSelection()
             self._control.setTextCursor(cursor)
             self._filter_drag = False
 
         # Ensure that drops are safe.
         elif etype == QtCore.QEvent.Drop and obj == self._control.viewport():
             cursor = self._control.cursorForPosition(event.pos())
             if self._in_buffer(cursor.position()):
                 text = event.mimeData().text()
                 self._insert_plain_text_into_buffer(cursor, text)
 
             # Qt is expecting to get something here--drag and drop occurs in its
             # own event loop. Send a DragLeave event to end it.
             QtGui.qApp.sendEvent(obj, QtGui.QDragLeaveEvent())
             return True
 
         # Handle scrolling of the vsplit pager. This hack attempts to solve
         # problems with tearing of the help text inside the pager window.  This
         # happens only on Mac OS X with both PySide and PyQt. This fix isn't
         # perfect but makes the pager more usable.
         elif etype in self._pager_scroll_events and \
                 obj == self._page_control:
             self._page_control.repaint()
             return True
         return super(ConsoleWidget, self).eventFilter(obj, event)
 
     #---------------------------------------------------------------------------
     # 'QWidget' interface
     #---------------------------------------------------------------------------
 
     def sizeHint(self):
         """ Reimplemented to suggest a size that is 80 characters wide and
             25 lines high.
         """
         font_metrics = QtGui.QFontMetrics(self.font)
         margin = (self._control.frameWidth() +
                   self._control.document().documentMargin()) * 2
         style = self.style()
         splitwidth = style.pixelMetric(QtGui.QStyle.PM_SplitterWidth)
 
         # Note 1: Despite my best efforts to take the various margins into
         # account, the width is still coming out a bit too small, so we include
         # a fudge factor of one character here.
         # Note 2: QFontMetrics.maxWidth is not used here or anywhere else due
         # to a Qt bug on certain Mac OS systems where it returns 0.
         width = font_metrics.width(' ') * 81 + margin
         width += style.pixelMetric(QtGui.QStyle.PM_ScrollBarExtent)
         if self.paging == 'hsplit':
             width = width * 2 + splitwidth
 
         height = font_metrics.height() * 25 + margin
         if self.paging == 'vsplit':
             height = height * 2 + splitwidth
 
         return QtCore.QSize(width, height)
 
     #---------------------------------------------------------------------------
     # 'ConsoleWidget' public interface
     #---------------------------------------------------------------------------
 
     def can_copy(self):
         """ Returns whether text can be copied to the clipboard.
         """
         return self._control.textCursor().hasSelection()
 
     def can_cut(self):
         """ Returns whether text can be cut to the clipboard.
         """
         cursor = self._control.textCursor()
         return (cursor.hasSelection() and
                 self._in_buffer(cursor.anchor()) and
                 self._in_buffer(cursor.position()))
 
     def can_paste(self):
         """ Returns whether text can be pasted from the clipboard.
         """
         if self._control.textInteractionFlags() & QtCore.Qt.TextEditable:
             return bool(QtGui.QApplication.clipboard().text())
         return False
 
     def clear(self, keep_input=True):
         """ Clear the console.
 
         Parameters:
         -----------
         keep_input : bool, optional (default True)
             If set, restores the old input buffer if a new prompt is written.
         """
         if self._executing:
             self._control.clear()
         else:
             if keep_input:
                 input_buffer = self.input_buffer
             self._control.clear()
             self._show_prompt()
             if keep_input:
                 self.input_buffer = input_buffer
 
     def copy(self):
         """ Copy the currently selected text to the clipboard.
         """
         self.layout().currentWidget().copy()
 
     def cut(self):
         """ Copy the currently selected text to the clipboard and delete it
             if it's inside the input buffer.
         """
         self.copy()
         if self.can_cut():
             self._control.textCursor().removeSelectedText()
 
     def execute(self, source=None, hidden=False, interactive=False):
         """ Executes source or the input buffer, possibly prompting for more
         input.
 
         Parameters:
         -----------
         source : str, optional
 
             The source to execute. If not specified, the input buffer will be
             used. If specified and 'hidden' is False, the input buffer will be
             replaced with the source before execution.
 
         hidden : bool, optional (default False)
 
             If set, no output will be shown and the prompt will not be modified.
             In other words, it will be completely invisible to the user that
             an execution has occurred.
 
         interactive : bool, optional (default False)
 
             Whether the console is to treat the source as having been manually
             entered by the user. The effect of this parameter depends on the
             subclass implementation.
 
         Raises:
         -------
         RuntimeError
             If incomplete input is given and 'hidden' is True. In this case,
             it is not possible to prompt for more input.
 
         Returns:
         --------
         A boolean indicating whether the source was executed.
         """
         # WARNING: The order in which things happen here is very particular, in
         # large part because our syntax highlighting is fragile. If you change
         # something, test carefully!
 
         # Decide what to execute.
         if source is None:
             source = self.input_buffer
             if not hidden:
                 # A newline is appended later, but it should be considered part
                 # of the input buffer.
                 source += '\n'
         elif not hidden:
             self.input_buffer = source
 
         # Execute the source or show a continuation prompt if it is incomplete.
         complete = self._is_complete(source, interactive)
         if hidden:
             if complete:
                 self._execute(source, hidden)
             else:
                 error = 'Incomplete noninteractive input: "%s"'
                 raise RuntimeError(error % source)
         else:
             if complete:
                 self._append_plain_text('\n')
                 self._input_buffer_executing = self.input_buffer
                 self._executing = True
                 self._prompt_finished()
 
                 # The maximum block count is only in effect during execution.
                 # This ensures that _prompt_pos does not become invalid due to
                 # text truncation.
                 self._control.document().setMaximumBlockCount(self.buffer_size)
 
                 # Setting a positive maximum block count will automatically
                 # disable the undo/redo history, but just to be safe:
                 self._control.setUndoRedoEnabled(False)
 
                 # Perform actual execution.
                 self._execute(source, hidden)
 
             else:
                 # Do this inside an edit block so continuation prompts are
                 # removed seamlessly via undo/redo.
                 cursor = self._get_end_cursor()
                 cursor.beginEditBlock()
                 cursor.insertText('\n')
                 self._insert_continuation_prompt(cursor)
                 cursor.endEditBlock()
 
                 # Do not do this inside the edit block. It works as expected
                 # when using a QPlainTextEdit control, but does not have an
                 # effect when using a QTextEdit. I believe this is a Qt bug.
                 self._control.moveCursor(QtGui.QTextCursor.End)
 
         return complete
 
     def export_html(self):
         """ Shows a dialog to export HTML/XML in various formats.
         """
         self._html_exporter.export()
 
     def _get_input_buffer(self, force=False):
         """ The text that the user has entered entered at the current prompt.
 
         If the console is currently executing, the text that is executing will
         always be returned.
         """
         # If we're executing, the input buffer may not even exist anymore due to
         # the limit imposed by 'buffer_size'. Therefore, we store it.
         if self._executing and not force:
             return self._input_buffer_executing
 
         cursor = self._get_end_cursor()
         cursor.setPosition(self._prompt_pos, QtGui.QTextCursor.KeepAnchor)
         input_buffer = cursor.selection().toPlainText()
 
         # Strip out continuation prompts.
         return input_buffer.replace('\n' + self._continuation_prompt, '\n')
 
     def _set_input_buffer(self, string):
         """ Sets the text in the input buffer.
 
         If the console is currently executing, this call has no *immediate*
         effect. When the execution is finished, the input buffer will be updated
         appropriately.
         """
         # If we're executing, store the text for later.
         if self._executing:
             self._input_buffer_pending = string
             return
 
         # Remove old text.
         cursor = self._get_end_cursor()
         cursor.beginEditBlock()
         cursor.setPosition(self._prompt_pos, QtGui.QTextCursor.KeepAnchor)
         cursor.removeSelectedText()
 
         # Insert new text with continuation prompts.
         self._insert_plain_text_into_buffer(self._get_prompt_cursor(), string)
         cursor.endEditBlock()
         self._control.moveCursor(QtGui.QTextCursor.End)
 
     input_buffer = property(_get_input_buffer, _set_input_buffer)
 
     def _get_font(self):
         """ The base font being used by the ConsoleWidget.
         """
         return self._control.document().defaultFont()
 
     def _set_font(self, font):
         """ Sets the base font for the ConsoleWidget to the specified QFont.
         """
         font_metrics = QtGui.QFontMetrics(font)
         self._control.setTabStopWidth(self.tab_width * font_metrics.width(' '))
 
         self._completion_widget.setFont(font)
         self._control.document().setDefaultFont(font)
         if self._page_control:
             self._page_control.document().setDefaultFont(font)
 
         self.font_changed.emit(font)
 
     font = property(_get_font, _set_font)
 
     def paste(self, mode=QtGui.QClipboard.Clipboard):
         """ Paste the contents of the clipboard into the input region.
 
         Parameters:
         -----------
         mode : QClipboard::Mode, optional [default QClipboard::Clipboard]
 
             Controls which part of the system clipboard is used. This can be
             used to access the selection clipboard in X11 and the Find buffer
             in Mac OS. By default, the regular clipboard is used.
         """
         if self._control.textInteractionFlags() & QtCore.Qt.TextEditable:
             # Make sure the paste is safe.
             self._keep_cursor_in_buffer()
             cursor = self._control.textCursor()
 
             # Remove any trailing newline, which confuses the GUI and forces the
             # user to backspace.
             text = QtGui.QApplication.clipboard().text(mode).rstrip()
             self._insert_plain_text_into_buffer(cursor, dedent(text))
 
     def print_(self, printer = None):
         """ Print the contents of the ConsoleWidget to the specified QPrinter.
         """
         if (not printer):
             printer = QtGui.QPrinter()
             if(QtGui.QPrintDialog(printer).exec_() != QtGui.QDialog.Accepted):
                 return
         self._control.print_(printer)
 
     def prompt_to_top(self):
         """ Moves the prompt to the top of the viewport.
         """
         if not self._executing:
             prompt_cursor = self._get_prompt_cursor()
             if self._get_cursor().blockNumber() < prompt_cursor.blockNumber():
                 self._set_cursor(prompt_cursor)
             self._set_top_cursor(prompt_cursor)
 
     def redo(self):
         """ Redo the last operation. If there is no operation to redo, nothing
             happens.
         """
         self._control.redo()
 
     def reset_font(self):
         """ Sets the font to the default fixed-width font for this platform.
         """
         if sys.platform == 'win32':
             # Consolas ships with Vista/Win7, fallback to Courier if needed
             fallback = 'Courier'
         elif sys.platform == 'darwin':
             # OSX always has Monaco
             fallback = 'Monaco'
         else:
             # Monospace should always exist
             fallback = 'Monospace'
         font = get_font(self.font_family, fallback)
         if self.font_size:
             font.setPointSize(self.font_size)
         else:
             font.setPointSize(QtGui.qApp.font().pointSize())
         font.setStyleHint(QtGui.QFont.TypeWriter)
         self._set_font(font)
 
     def change_font_size(self, delta):
         """Change the font size by the specified amount (in points).
         """
         font = self.font
         size = max(font.pointSize() + delta, 1) # minimum 1 point
         font.setPointSize(size)
         self._set_font(font)
 
     def _increase_font_size(self):
         self.change_font_size(1)
 
     def _decrease_font_size(self):
         self.change_font_size(-1)
 
     def select_all(self):
         """ Selects all the text in the buffer.
         """
         self._control.selectAll()
 
     def _get_tab_width(self):
         """ The width (in terms of space characters) for tab characters.
         """
         return self._tab_width
 
     def _set_tab_width(self, tab_width):
         """ Sets the width (in terms of space characters) for tab characters.
         """
         font_metrics = QtGui.QFontMetrics(self.font)
         self._control.setTabStopWidth(tab_width * font_metrics.width(' '))
 
         self._tab_width = tab_width
 
     tab_width = property(_get_tab_width, _set_tab_width)
 
     def undo(self):
         """ Undo the last operation. If there is no operation to undo, nothing
             happens.
         """
         self._control.undo()
 
     #---------------------------------------------------------------------------
     # 'ConsoleWidget' abstract interface
     #---------------------------------------------------------------------------
 
     def _is_complete(self, source, interactive):
         """ Returns whether 'source' can be executed. When triggered by an
             Enter/Return key press, 'interactive' is True; otherwise, it is
             False.
         """
         raise NotImplementedError
 
     def _execute(self, source, hidden):
         """ Execute 'source'. If 'hidden', do not show any output.
         """
         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, shift_modifier):
         """ Called when the up key is pressed. Returns whether to continue
             processing the event.
         """
         return True
 
     def _down_pressed(self, shift_modifier):
         """ 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 _append_custom(self, insert, input, before_prompt=False):
         """ A low-level method for appending content to the end of the buffer.
 
         If 'before_prompt' is enabled, the content will be inserted before the
         current prompt, if there is one.
         """
         # Determine where to insert the content.
         cursor = self._control.textCursor()
         if before_prompt and (self._reading or not self._executing):
             cursor.setPosition(self._append_before_prompt_pos)
         else:
             cursor.movePosition(QtGui.QTextCursor.End)
         start_pos = cursor.position()
 
         # Perform the insertion.
         result = insert(cursor, input)
 
         # Adjust the prompt position if we have inserted before it. This is safe
         # because buffer truncation is disabled when not executing.
         if before_prompt and not self._executing:
             diff = cursor.position() - start_pos
             self._append_before_prompt_pos += diff
             self._prompt_pos += diff
 
         return result
 
     def _append_html(self, html, before_prompt=False):
         """ Appends HTML at the end of the console buffer.
         """
         self._append_custom(self._insert_html, html, before_prompt)
 
     def _append_html_fetching_plain_text(self, html, before_prompt=False):
         """ Appends HTML, then returns the plain text version of it.
         """
         return self._append_custom(self._insert_html_fetching_plain_text,
                                    html, before_prompt)
 
     def _append_plain_text(self, text, before_prompt=False):
         """ Appends plain text, processing ANSI codes if enabled.
         """
         self._append_custom(self._insert_plain_text, text, before_prompt)
 
     def _cancel_text_completion(self):
         """ If text completion is progress, cancel it.
         """
         if self._text_completing_pos:
             self._clear_temporary_buffer()
             self._text_completing_pos = 0
 
     def _clear_temporary_buffer(self):
         """ Clears the "temporary text" buffer, i.e. all the text following
             the prompt region.
         """
         # Select and remove all text below the input buffer.
         cursor = self._get_prompt_cursor()
         prompt = self._continuation_prompt.lstrip()
         while cursor.movePosition(QtGui.QTextCursor.NextBlock):
             temp_cursor = QtGui.QTextCursor(cursor)
             temp_cursor.select(QtGui.QTextCursor.BlockUnderCursor)
             text = temp_cursor.selection().toPlainText().lstrip()
             if not text.startswith(prompt):
                 break
         else:
             # We've reached the end of the input buffer and no text follows.
             return
         cursor.movePosition(QtGui.QTextCursor.Left) # Grab the newline.
         cursor.movePosition(QtGui.QTextCursor.End,
                             QtGui.QTextCursor.KeepAnchor)
         cursor.removeSelectedText()
 
         # After doing this, we have no choice but to clear the undo/redo
         # history. Otherwise, the text is not "temporary" at all, because it
         # can be recalled with undo/redo. Unfortunately, Qt does not expose
         # fine-grained control to the undo/redo system.
         if self._control.isUndoRedoEnabled():
             self._control.setUndoRedoEnabled(False)
             self._control.setUndoRedoEnabled(True)
 
     def _complete_with_items(self, cursor, items):
         """ Performs completion with 'items' at the specified cursor location.
         """
         self._cancel_text_completion()
 
         if len(items) == 1:
             cursor.setPosition(self._control.textCursor().position(),
                                QtGui.QTextCursor.KeepAnchor)
             cursor.insertText(items[0])
 
         elif len(items) > 1:
             current_pos = self._control.textCursor().position()
             prefix = commonprefix(items)
             if prefix:
                 cursor.setPosition(current_pos, QtGui.QTextCursor.KeepAnchor)
                 cursor.insertText(prefix)
                 current_pos = cursor.position()
 
             if self.gui_completion:
                 cursor.movePosition(QtGui.QTextCursor.Left, n=len(prefix))
                 self._completion_widget.show_items(cursor, items)
             else:
                 cursor.beginEditBlock()
                 self._append_plain_text('\n')
                 self._page(self._format_as_columns(items))
                 cursor.endEditBlock()
 
                 cursor.setPosition(current_pos)
                 self._control.moveCursor(QtGui.QTextCursor.End)
                 self._control.setTextCursor(cursor)
                 self._text_completing_pos = current_pos
 
     def _context_menu_make(self, pos):
         """ Creates a context menu for the given QPoint (in widget coordinates).
         """
         menu = QtGui.QMenu(self)
 
         self.cut_action = menu.addAction('Cut', self.cut)
         self.cut_action.setEnabled(self.can_cut())
         self.cut_action.setShortcut(QtGui.QKeySequence.Cut)
 
         self.copy_action = menu.addAction('Copy', self.copy)
         self.copy_action.setEnabled(self.can_copy())
         self.copy_action.setShortcut(QtGui.QKeySequence.Copy)
 
         self.paste_action = menu.addAction('Paste', self.paste)
         self.paste_action.setEnabled(self.can_paste())
         self.paste_action.setShortcut(QtGui.QKeySequence.Paste)
 
         menu.addSeparator()
         menu.addAction(self.select_all_action)
 
         menu.addSeparator()
         menu.addAction(self.export_action)
         menu.addAction(self.print_action)
 
         return menu
 
     def _control_key_down(self, modifiers, include_command=False):
         """ Given a KeyboardModifiers flags object, return whether the Control
         key is down.
 
         Parameters:
         -----------
         include_command : bool, optional (default True)
             Whether to treat the Command key as a (mutually exclusive) synonym
             for Control when in Mac OS.
         """
         # Note that on Mac OS, ControlModifier corresponds to the Command key
         # while MetaModifier corresponds to the Control key.
         if sys.platform == 'darwin':
             down = include_command and (modifiers & QtCore.Qt.ControlModifier)
             return bool(down) ^ bool(modifiers & QtCore.Qt.MetaModifier)
         else:
             return bool(modifiers & QtCore.Qt.ControlModifier)
 
     def _create_control(self):
         """ Creates and connects the underlying text widget.
         """
         # Create the underlying control.
         if self.kind == 'plain':
             control = QtGui.QPlainTextEdit()
         elif self.kind == 'rich':
             control = QtGui.QTextEdit()
             control.setAcceptRichText(False)
 
         # Install event filters. The filter on the viewport is needed for
         # mouse events and drag events.
         control.installEventFilter(self)
         control.viewport().installEventFilter(self)
 
         # Connect signals.
         control.cursorPositionChanged.connect(self._cursor_position_changed)
         control.customContextMenuRequested.connect(
             self._custom_context_menu_requested)
         control.copyAvailable.connect(self.copy_available)
         control.redoAvailable.connect(self.redo_available)
         control.undoAvailable.connect(self.undo_available)
 
         # Hijack the document size change signal to prevent Qt from adjusting
         # the viewport's scrollbar. We are relying on an implementation detail
         # of Q(Plain)TextEdit here, which is potentially dangerous, but without
         # this functionality we cannot create a nice terminal interface.
         layout = control.document().documentLayout()
         layout.documentSizeChanged.disconnect()
         layout.documentSizeChanged.connect(self._adjust_scrollbars)
 
         # Configure the control.
         control.setAttribute(QtCore.Qt.WA_InputMethodEnabled, True)
         control.setContextMenuPolicy(QtCore.Qt.CustomContextMenu)
         control.setReadOnly(True)
         control.setUndoRedoEnabled(False)
         control.setVerticalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOn)
         return control
 
     def _create_page_control(self):
         """ Creates and connects the underlying paging widget.
         """
         if self.kind == 'plain':
             control = QtGui.QPlainTextEdit()
         elif self.kind == 'rich':
             control = QtGui.QTextEdit()
         control.installEventFilter(self)
         viewport = control.viewport()
         viewport.installEventFilter(self)
         control.setReadOnly(True)
         control.setUndoRedoEnabled(False)
         control.setVerticalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOn)
         return control
 
     def _event_filter_console_keypress(self, event):
         """ Filter key events for the underlying text widget to create a
             console-like interface.
         """
         intercepted = False
         cursor = self._control.textCursor()
         position = cursor.position()
         key = event.key()
         ctrl_down = self._control_key_down(event.modifiers())
         alt_down = event.modifiers() & QtCore.Qt.AltModifier
         shift_down = event.modifiers() & QtCore.Qt.ShiftModifier
 
         #------ Special sequences ----------------------------------------------
 
         if event.matches(QtGui.QKeySequence.Copy):
             self.copy()
             intercepted = True
 
         elif event.matches(QtGui.QKeySequence.Cut):
             self.cut()
             intercepted = True
 
         elif event.matches(QtGui.QKeySequence.Paste):
             self.paste()
             intercepted = True
 
         #------ Special modifier logic -----------------------------------------
 
         elif key in (QtCore.Qt.Key_Return, QtCore.Qt.Key_Enter):
             intercepted = True
 
             # Special handling when tab completing in text mode.
             self._cancel_text_completion()
 
             if self._in_buffer(position):
                 # Special handling when a reading a line of raw input.
                 if self._reading:
                     self._append_plain_text('\n')
                     self._reading = False
                     if self._reading_callback:
                         self._reading_callback()
 
                 # If the input buffer is a single line or there is only
                 # whitespace after the cursor, execute. Otherwise, split the
                 # line with a continuation prompt.
                 elif not self._executing:
                     cursor.movePosition(QtGui.QTextCursor.End,
                                         QtGui.QTextCursor.KeepAnchor)
                     at_end = len(cursor.selectedText().strip()) == 0
                     single_line = (self._get_end_cursor().blockNumber() ==
                                    self._get_prompt_cursor().blockNumber())
                     if (at_end or shift_down or single_line) and not ctrl_down:
                         self.execute(interactive = not shift_down)
                     else:
                         # Do this inside an edit block for clean undo/redo.
                         cursor.beginEditBlock()
                         cursor.setPosition(position)
                         cursor.insertText('\n')
                         self._insert_continuation_prompt(cursor)
                         cursor.endEditBlock()
 
                         # Ensure that the whole input buffer is visible.
                         # FIXME: This will not be usable if the input buffer is
                         # taller than the console widget.
                         self._control.moveCursor(QtGui.QTextCursor.End)
                         self._control.setTextCursor(cursor)
 
         #------ Control/Cmd modifier -------------------------------------------
 
         elif ctrl_down:
             if key == QtCore.Qt.Key_G:
                 self._keyboard_quit()
                 intercepted = True
 
             elif key == QtCore.Qt.Key_K:
                 if self._in_buffer(position):
                     cursor.clearSelection()
                     cursor.movePosition(QtGui.QTextCursor.EndOfLine,
                                         QtGui.QTextCursor.KeepAnchor)
                     if not cursor.hasSelection():
                         # Line deletion (remove continuation prompt)
                         cursor.movePosition(QtGui.QTextCursor.NextBlock,
                                             QtGui.QTextCursor.KeepAnchor)
                         cursor.movePosition(QtGui.QTextCursor.Right,
                                             QtGui.QTextCursor.KeepAnchor,
                                             len(self._continuation_prompt))
                     self._kill_ring.kill_cursor(cursor)
                     self._set_cursor(cursor)
                 intercepted = True
 
             elif key == QtCore.Qt.Key_L:
                 self.prompt_to_top()
                 intercepted = True
 
             elif key == QtCore.Qt.Key_O:
                 if self._page_control and self._page_control.isVisible():
                     self._page_control.setFocus()
                 intercepted = True
 
             elif key == QtCore.Qt.Key_U:
                 if self._in_buffer(position):
                     cursor.clearSelection()
                     start_line = cursor.blockNumber()
                     if start_line == self._get_prompt_cursor().blockNumber():
                         offset = len(self._prompt)
                     else:
                         offset = len(self._continuation_prompt)
                     cursor.movePosition(QtGui.QTextCursor.StartOfBlock,
                                         QtGui.QTextCursor.KeepAnchor)
                     cursor.movePosition(QtGui.QTextCursor.Right,
                                         QtGui.QTextCursor.KeepAnchor, offset)
                     self._kill_ring.kill_cursor(cursor)
                     self._set_cursor(cursor)
                 intercepted = True
 
             elif key == QtCore.Qt.Key_Y:
                 self._keep_cursor_in_buffer()
                 self._kill_ring.yank()
                 intercepted = True
 
             elif key in (QtCore.Qt.Key_Backspace, QtCore.Qt.Key_Delete):
                 if key == QtCore.Qt.Key_Backspace:
                     cursor = self._get_word_start_cursor(position)
                 else: # key == QtCore.Qt.Key_Delete
                     cursor = self._get_word_end_cursor(position)
                 cursor.setPosition(position, QtGui.QTextCursor.KeepAnchor)
                 self._kill_ring.kill_cursor(cursor)
                 intercepted = True
 
             elif key == QtCore.Qt.Key_D:
                 if len(self.input_buffer) == 0:
                     self.exit_requested.emit(self)
                 else:
                     new_event = QtGui.QKeyEvent(QtCore.QEvent.KeyPress,
                                                 QtCore.Qt.Key_Delete,
                                                 QtCore.Qt.NoModifier)
                     QtGui.qApp.sendEvent(self._control, new_event)
                     intercepted = True
 
         #------ Alt modifier ---------------------------------------------------
 
         elif alt_down:
             if key == QtCore.Qt.Key_B:
                 self._set_cursor(self._get_word_start_cursor(position))
                 intercepted = True
 
             elif key == QtCore.Qt.Key_F:
                 self._set_cursor(self._get_word_end_cursor(position))
                 intercepted = True
 
             elif key == QtCore.Qt.Key_Y:
                 self._kill_ring.rotate()
                 intercepted = True
 
             elif key == QtCore.Qt.Key_Backspace:
                 cursor = self._get_word_start_cursor(position)
                 cursor.setPosition(position, QtGui.QTextCursor.KeepAnchor)
                 self._kill_ring.kill_cursor(cursor)
                 intercepted = True
 
             elif key == QtCore.Qt.Key_D:
                 cursor = self._get_word_end_cursor(position)
                 cursor.setPosition(position, QtGui.QTextCursor.KeepAnchor)
                 self._kill_ring.kill_cursor(cursor)
                 intercepted = True
 
             elif key == QtCore.Qt.Key_Delete:
                 intercepted = True
 
             elif key == QtCore.Qt.Key_Greater:
                 self._control.moveCursor(QtGui.QTextCursor.End)
                 intercepted = True
 
             elif key == QtCore.Qt.Key_Less:
                 self._control.setTextCursor(self._get_prompt_cursor())
                 intercepted = True
 
         #------ No modifiers ---------------------------------------------------
 
         else:
             if shift_down:
                 anchormode = QtGui.QTextCursor.KeepAnchor
             else:
                 anchormode = QtGui.QTextCursor.MoveAnchor
 
             if key == QtCore.Qt.Key_Escape:
                 self._keyboard_quit()
                 intercepted = True
 
             elif key == QtCore.Qt.Key_Up:
                 if self._reading or not self._up_pressed(shift_down):
                     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(shift_down):
                     intercepted = True
                 else:
                     end_line = self._get_end_cursor().blockNumber()
                     intercepted = cursor.blockNumber() == end_line
 
             elif key == QtCore.Qt.Key_Tab:
                 if not self._reading:
                     if self._tab_pressed():
                         # real tab-key, insert four spaces
                         cursor.insertText(' '*4)
                     intercepted = True
 
             elif key == QtCore.Qt.Key_Left:
 
                 # Move to the previous line
                 line, col = cursor.blockNumber(), cursor.columnNumber()
                 if line > self._get_prompt_cursor().blockNumber() and \
                         col == len(self._continuation_prompt):
                     self._control.moveCursor(QtGui.QTextCursor.PreviousBlock,
                                              mode=anchormode)
                     self._control.moveCursor(QtGui.QTextCursor.EndOfBlock,
                                              mode=anchormode)
                     intercepted = True
 
                 # Regular left movement
                 else:
                     intercepted = not self._in_buffer(position - 1)
 
             elif key == QtCore.Qt.Key_Right:
                 original_block_number = cursor.blockNumber()
                 cursor.movePosition(QtGui.QTextCursor.Right,
                                 mode=anchormode)
                 if cursor.blockNumber() != original_block_number:
                     cursor.movePosition(QtGui.QTextCursor.Right,
                                         n=len(self._continuation_prompt),
                                         mode=anchormode)
                 self._set_cursor(cursor)
                 intercepted = True
 
             elif key == QtCore.Qt.Key_Home:
                 start_line = cursor.blockNumber()
                 if start_line == self._get_prompt_cursor().blockNumber():
                     start_pos = self._prompt_pos
                 else:
                     cursor.movePosition(QtGui.QTextCursor.StartOfBlock,
                                         QtGui.QTextCursor.KeepAnchor)
                     start_pos = cursor.position()
                     start_pos += len(self._continuation_prompt)
                     cursor.setPosition(position)
                 if shift_down and self._in_buffer(position):
                     cursor.setPosition(start_pos, QtGui.QTextCursor.KeepAnchor)
                 else:
                     cursor.setPosition(start_pos)
                 self._set_cursor(cursor)
                 intercepted = True
 
             elif key == QtCore.Qt.Key_Backspace:
 
                 # Line deletion (remove continuation prompt)
                 line, col = cursor.blockNumber(), cursor.columnNumber()
                 if not self._reading and \
                         col == len(self._continuation_prompt) and \
                         line > self._get_prompt_cursor().blockNumber():
                     cursor.beginEditBlock()
                     cursor.movePosition(QtGui.QTextCursor.StartOfBlock,
                                         QtGui.QTextCursor.KeepAnchor)
                     cursor.removeSelectedText()
                     cursor.deletePreviousChar()
                     cursor.endEditBlock()
                     intercepted = True
 
                 # 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:
 
                 # Line deletion (remove continuation prompt)
                 if not self._reading and self._in_buffer(position) and \
                         cursor.atBlockEnd() and not cursor.hasSelection():
                     cursor.movePosition(QtGui.QTextCursor.NextBlock,
                                         QtGui.QTextCursor.KeepAnchor)
                     cursor.movePosition(QtGui.QTextCursor.Right,
                                         QtGui.QTextCursor.KeepAnchor,
                                         len(self._continuation_prompt))
                     cursor.removeSelectedText()
                     intercepted = True
 
                 # Regular forwards deletion:
                 else:
                     anchor = cursor.anchor()
                     intercepted = (not self._in_buffer(anchor) or
                                    not self._in_buffer(position))
 
         # Don't move the cursor if Control/Cmd is pressed to allow copy-paste
         # using the keyboard in any part of the buffer. Also, permit scrolling
         # with Page Up/Down keys. Finally, if we're executing, don't move the
         # cursor (if even this made sense, we can't guarantee that the prompt
         # position is still valid due to text truncation).
         if not (self._control_key_down(event.modifiers(), include_command=True)
                 or key in (QtCore.Qt.Key_PageUp, QtCore.Qt.Key_PageDown)
                 or (self._executing and not self._reading)):
             self._keep_cursor_in_buffer()
 
         return intercepted
 
     def _event_filter_page_keypress(self, event):
         """ Filter key events for the paging widget to create console-like
             interface.
         """
         key = event.key()
         ctrl_down = self._control_key_down(event.modifiers())
         alt_down = event.modifiers() & QtCore.Qt.AltModifier
 
         if ctrl_down:
             if key == QtCore.Qt.Key_O:
                 self._control.setFocus()
                 intercept = True
 
         elif alt_down:
             if key == QtCore.Qt.Key_Greater:
                 self._page_control.moveCursor(QtGui.QTextCursor.End)
                 intercepted = True
 
             elif key == QtCore.Qt.Key_Less:
                 self._page_control.moveCursor(QtGui.QTextCursor.Start)
                 intercepted = True
 
         elif key in (QtCore.Qt.Key_Q, QtCore.Qt.Key_Escape):
             if self._splitter:
                 self._page_control.hide()
                 self._control.setFocus()
             else:
                 self.layout().setCurrentWidget(self._control)
             return True
 
         elif key in (QtCore.Qt.Key_Enter, QtCore.Qt.Key_Return,
                      QtCore.Qt.Key_Tab):
             new_event = QtGui.QKeyEvent(QtCore.QEvent.KeyPress,
                                         QtCore.Qt.Key_PageDown,
                                         QtCore.Qt.NoModifier)
             QtGui.qApp.sendEvent(self._page_control, new_event)
             return True
 
         elif key == QtCore.Qt.Key_Backspace:
             new_event = QtGui.QKeyEvent(QtCore.QEvent.KeyPress,
                                         QtCore.Qt.Key_PageUp,
                                         QtCore.Qt.NoModifier)
             QtGui.qApp.sendEvent(self._page_control, new_event)
             return True
 
         return False
 
     def _format_as_columns(self, items, separator='  '):
         """ Transform a list of strings into a single string with columns.
 
         Parameters
         ----------
         items : sequence of strings
             The strings to process.
 
         separator : str, optional [default is two spaces]
             The string that separates columns.
 
         Returns
         -------
         The formatted string.
         """
         # Calculate the number of characters available.
         width = self._control.viewport().width()
         char_width = QtGui.QFontMetrics(self.font).width(' ')
         displaywidth = max(10, (width / char_width) - 1)
 
         return columnize(items, separator, displaywidth)
 
     def _get_block_plain_text(self, block):
         """ Given a QTextBlock, return its unformatted text.
         """
         cursor = QtGui.QTextCursor(block)
         cursor.movePosition(QtGui.QTextCursor.StartOfBlock)
         cursor.movePosition(QtGui.QTextCursor.EndOfBlock,
                             QtGui.QTextCursor.KeepAnchor)
         return cursor.selection().toPlainText()
 
     def _get_cursor(self):
         """ Convenience method that returns a cursor for the current position.
         """
         return self._control.textCursor()
 
     def _get_end_cursor(self):
         """ Convenience method that returns a cursor for the last character.
         """
         cursor = self._control.textCursor()
         cursor.movePosition(QtGui.QTextCursor.End)
         return cursor
 
     def _get_input_buffer_cursor_column(self):
         """ Returns the column of the cursor in the input buffer, excluding the
             contribution by the prompt, or -1 if there is no such column.
         """
         prompt = self._get_input_buffer_cursor_prompt()
         if prompt is None:
             return -1
         else:
             cursor = self._control.textCursor()
             return cursor.columnNumber() - len(prompt)
 
     def _get_input_buffer_cursor_line(self):
         """ Returns the text of the line of the input buffer that contains the
             cursor, or None if there is no such line.
         """
         prompt = self._get_input_buffer_cursor_prompt()
         if prompt is None:
             return None
         else:
             cursor = self._control.textCursor()
             text = self._get_block_plain_text(cursor.block())
             return text[len(prompt):]
 
     def _get_input_buffer_cursor_prompt(self):
         """ Returns the (plain text) prompt for line of the input buffer that
             contains the cursor, or None if there is no such line.
         """
         if self._executing:
             return None
         cursor = self._control.textCursor()
         if cursor.position() >= self._prompt_pos:
             if cursor.blockNumber() == self._get_prompt_cursor().blockNumber():
                 return self._prompt
             else:
                 return self._continuation_prompt
         else:
             return None
 
     def _get_prompt_cursor(self):
         """ Convenience method that returns a cursor for the prompt position.
         """
         cursor = self._control.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._control.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._control.document()
         position -= 1
         while position >= self._prompt_pos and \
                   not is_letter_or_number(document.characterAt(position)):
             position -= 1
         while position >= self._prompt_pos and \
                   is_letter_or_number(document.characterAt(position)):
             position -= 1
         cursor = self._control.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._control.document()
         end = self._get_end_cursor().position()
         while position < end and \
                   not is_letter_or_number(document.characterAt(position)):
             position += 1
         while position < end and \
                   is_letter_or_number(document.characterAt(position)):
             position += 1
         cursor = self._control.textCursor()
         cursor.setPosition(position)
         return cursor
 
     def _insert_continuation_prompt(self, cursor):
         """ Inserts new continuation prompt using the specified cursor.
         """
         if self._continuation_prompt_html is None:
             self._insert_plain_text(cursor, self._continuation_prompt)
         else:
             self._continuation_prompt = self._insert_html_fetching_plain_text(
                 cursor, self._continuation_prompt_html)
 
     def _insert_html(self, cursor, html):
         """ Inserts HTML using the specified cursor in such a way that future
             formatting is unaffected.
         """
         cursor.beginEditBlock()
         cursor.insertHtml(html)
 
         # After inserting HTML, the text document "remembers" it's in "html
         # mode", which means that subsequent calls adding plain text will result
         # in unwanted formatting, lost tab characters, etc. The following code
         # hacks around this behavior, which I consider to be a bug in Qt, by
         # (crudely) resetting the document's style state.
         cursor.movePosition(QtGui.QTextCursor.Left,
                             QtGui.QTextCursor.KeepAnchor)
         if cursor.selection().toPlainText() == ' ':
             cursor.removeSelectedText()
         else:
             cursor.movePosition(QtGui.QTextCursor.Right)
         cursor.insertText(' ', QtGui.QTextCharFormat())
         cursor.endEditBlock()
 
     def _insert_html_fetching_plain_text(self, cursor, html):
         """ Inserts HTML using the specified cursor, then returns its plain text
             version.
         """
         cursor.beginEditBlock()
         cursor.removeSelectedText()
 
         start = cursor.position()
         self._insert_html(cursor, html)
         end = cursor.position()
         cursor.setPosition(start, QtGui.QTextCursor.KeepAnchor)
         text = cursor.selection().toPlainText()
 
         cursor.setPosition(end)
         cursor.endEditBlock()
         return text
 
     def _insert_plain_text(self, cursor, text):
         """ Inserts plain text using the specified cursor, processing ANSI codes
             if enabled.
         """
         cursor.beginEditBlock()
         if self.ansi_codes:
             for substring in self._ansi_processor.split_string(text):
                 for act in self._ansi_processor.actions:
 
                     # Unlike real terminal emulators, we don't distinguish
                     # between the screen and the scrollback buffer. A screen
                     # erase request clears everything.
                     if act.action == 'erase' and act.area == 'screen':
                         cursor.select(QtGui.QTextCursor.Document)
                         cursor.removeSelectedText()
 
                     # Simulate a form feed by scrolling just past the last line.
                     elif act.action == 'scroll' and act.unit == 'page':
                         cursor.insertText('\n')
                         cursor.endEditBlock()
                         self._set_top_cursor(cursor)
                         cursor.joinPreviousEditBlock()
                         cursor.deletePreviousChar()
 
                     elif act.action == 'carriage-return':
                         cursor.movePosition(
                             cursor.StartOfLine, cursor.KeepAnchor)
 
                     elif act.action == 'beep':
                         QtGui.qApp.beep()
 
                 format = self._ansi_processor.get_format()
                 cursor.insertText(substring, format)
         else:
             cursor.insertText(text)
         cursor.endEditBlock()
 
     def _insert_plain_text_into_buffer(self, cursor, text):
         """ Inserts text into the input buffer using the specified cursor (which
             must be in the input buffer), ensuring that continuation prompts are
             inserted as necessary.
         """
         lines = text.splitlines(True)
         if lines:
             cursor.beginEditBlock()
             cursor.insertText(lines[0])
             for line in lines[1:]:
                 if self._continuation_prompt_html is None:
                     cursor.insertText(self._continuation_prompt)
                 else:
                     self._continuation_prompt = \
                         self._insert_html_fetching_plain_text(
                             cursor, self._continuation_prompt_html)
                 cursor.insertText(line)
             cursor.endEditBlock()
 
     def _in_buffer(self, position=None):
         """ Returns whether the current cursor (or, if specified, a position) is
             inside the editing region.
         """
         cursor = self._control.textCursor()
         if position is None:
             position = cursor.position()
         else:
             cursor.setPosition(position)
         line = cursor.blockNumber()
         prompt_line = self._get_prompt_cursor().blockNumber()
         if line == prompt_line:
             return position >= self._prompt_pos
         elif line > prompt_line:
             cursor.movePosition(QtGui.QTextCursor.StartOfBlock)
             prompt_pos = cursor.position() + len(self._continuation_prompt)
             return position >= prompt_pos
         return False
 
     def _keep_cursor_in_buffer(self):
         """ Ensures that the cursor is inside the editing region. Returns
             whether the cursor was moved.
         """
         moved = not self._in_buffer()
         if moved:
             cursor = self._control.textCursor()
             cursor.movePosition(QtGui.QTextCursor.End)
             self._control.setTextCursor(cursor)
         return moved
 
     def _keyboard_quit(self):
         """ Cancels the current editing task ala Ctrl-G in Emacs.
         """
         if self._text_completing_pos:
             self._cancel_text_completion()
         else:
             self.input_buffer = ''
 
     def _page(self, text, html=False):
         """ Displays text using the pager if it exceeds the height of the
         viewport.
 
         Parameters:
         -----------
         html : bool, optional (default False)
             If set, the text will be interpreted as HTML instead of plain text.
         """
         line_height = QtGui.QFontMetrics(self.font).height()
         minlines = self._control.viewport().height() / line_height
         if self.paging != 'none' and \
                 re.match("(?:[^\n]*\n){%i}" % minlines, text):
             if self.paging == 'custom':
                 self.custom_page_requested.emit(text)
             else:
                 self._page_control.clear()
                 cursor = self._page_control.textCursor()
                 if html:
                     self._insert_html(cursor, text)
                 else:
                     self._insert_plain_text(cursor, text)
                 self._page_control.moveCursor(QtGui.QTextCursor.Start)
 
                 self._page_control.viewport().resize(self._control.size())
                 if self._splitter:
                     self._page_control.show()
                     self._page_control.setFocus()
                 else:
                     self.layout().setCurrentWidget(self._page_control)
         elif html:
             self._append_plain_html(text)
         else:
             self._append_plain_text(text)
 
     def _prompt_finished(self):
         """ Called immediately after a prompt is finished, i.e. when some input
             will be processed and a new prompt displayed.
         """
         self._control.setReadOnly(True)
         self._prompt_finished_hook()
 
     def _prompt_started(self):
         """ Called immediately after a new prompt is displayed.
         """
         # Temporarily disable the maximum block count to permit undo/redo and
         # to ensure that the prompt position does not change due to truncation.
         self._control.document().setMaximumBlockCount(0)
         self._control.setUndoRedoEnabled(True)
 
         # Work around bug in QPlainTextEdit: input method is not re-enabled
         # when read-only is disabled.
         self._control.setReadOnly(False)
         self._control.setAttribute(QtCore.Qt.WA_InputMethodEnabled, True)
 
         if not self._reading:
             self._executing = False
         self._prompt_started_hook()
 
         # If the input buffer has changed while executing, load it.
         if self._input_buffer_pending:
             self.input_buffer = self._input_buffer_pending
             self._input_buffer_pending = ''
 
         self._control.moveCursor(QtGui.QTextCursor.End)
 
     def _readline(self, prompt='', callback=None):
         """ Reads one line of input from the user.
 
         Parameters
         ----------
         prompt : str, optional
             The prompt to print before reading the line.
 
         callback : callable, optional
             A callback to execute with the read line. If not specified, input is
             read *synchronously* and this method does not return until it has
             been read.
 
         Returns
         -------
         If a callback is specified, returns nothing. Otherwise, returns the
         input string with the trailing newline stripped.
         """
         if self._reading:
             raise RuntimeError('Cannot read a line. Widget is already reading.')
 
         if not callback and not self.isVisible():
             # If the user cannot see the widget, this function cannot return.
             raise RuntimeError('Cannot synchronously read a line if the widget '
                                'is not visible!')
 
         self._reading = True
         self._show_prompt(prompt, newline=False)
 
         if callback is None:
             self._reading_callback = None
             while self._reading:
                 QtCore.QCoreApplication.processEvents()
             return self._get_input_buffer(force=True).rstrip('\n')
 
         else:
             self._reading_callback = lambda: \
                 callback(self._get_input_buffer(force=True).rstrip('\n'))
 
     def _set_continuation_prompt(self, prompt, html=False):
         """ Sets the continuation prompt.
 
         Parameters
         ----------
         prompt : str
             The prompt to show when more input is needed.
 
         html : bool, optional (default False)
             If set, the prompt will be inserted as formatted HTML. Otherwise,
             the prompt will be treated as plain text, though ANSI color codes
             will be handled.
         """
         if html:
             self._continuation_prompt_html = prompt
         else:
             self._continuation_prompt = prompt
             self._continuation_prompt_html = None
 
     def _set_cursor(self, cursor):
         """ Convenience method to set the current cursor.
         """
         self._control.setTextCursor(cursor)
 
     def _set_top_cursor(self, cursor):
         """ Scrolls the viewport so that the specified cursor is at the top.
         """
         scrollbar = self._control.verticalScrollBar()
         scrollbar.setValue(scrollbar.maximum())
         original_cursor = self._control.textCursor()
         self._control.setTextCursor(cursor)
         self._control.ensureCursorVisible()
         self._control.setTextCursor(original_cursor)
 
     def _show_prompt(self, prompt=None, html=False, newline=True):
         """ Writes a new prompt at the end of the buffer.
 
         Parameters
         ----------
         prompt : str, optional
             The prompt to show. If not specified, the previous prompt is used.
 
         html : bool, optional (default False)
             Only relevant when a prompt is specified. If set, the prompt will
             be inserted as formatted HTML. Otherwise, the prompt will be treated
             as plain text, though ANSI color codes will be handled.
 
         newline : bool, optional (default True)
             If set, a new line will be written before showing the prompt if
             there is not already a newline at the end of the buffer.
         """
         # Save the current end position to support _append*(before_prompt=True).
         cursor = self._get_end_cursor()
         self._append_before_prompt_pos = cursor.position()
 
         # Insert a preliminary newline, if necessary.
         if newline and cursor.position() > 0:
             cursor.movePosition(QtGui.QTextCursor.Left,
                                 QtGui.QTextCursor.KeepAnchor)
             if cursor.selection().toPlainText() != '\n':
                 self._append_plain_text('\n')
 
         # Write the prompt.
         self._append_plain_text(self._prompt_sep)
         if prompt is None:
             if self._prompt_html is None:
                 self._append_plain_text(self._prompt)
             else:
                 self._append_html(self._prompt_html)
         else:
             if html:
                 self._prompt = self._append_html_fetching_plain_text(prompt)
                 self._prompt_html = prompt
             else:
                 self._append_plain_text(prompt)
                 self._prompt = prompt
                 self._prompt_html = None
 
         self._prompt_pos = self._get_end_cursor().position()
         self._prompt_started()
 
     #------ Signal handlers ----------------------------------------------------
 
     def _adjust_scrollbars(self):
         """ Expands the vertical scrollbar beyond the range set by Qt.
         """
         # This code is adapted from _q_adjustScrollbars in qplaintextedit.cpp
         # and qtextedit.cpp.
         document = self._control.document()
         scrollbar = self._control.verticalScrollBar()
         viewport_height = self._control.viewport().height()
         if isinstance(self._control, QtGui.QPlainTextEdit):
             maximum = max(0, document.lineCount() - 1)
             step = viewport_height / self._control.fontMetrics().lineSpacing()
         else:
             # QTextEdit does not do line-based layout and blocks will not in
             # general have the same height. Therefore it does not make sense to
             # attempt to scroll in line height increments.
             maximum = document.size().height()
             step = viewport_height
         diff = maximum - scrollbar.maximum()
         scrollbar.setRange(0, maximum)
         scrollbar.setPageStep(step)
 
         # Compensate for undesirable scrolling that occurs automatically due to
         # maximumBlockCount() text truncation.
         if diff < 0 and document.blockCount() == document.maximumBlockCount():
             scrollbar.setValue(scrollbar.value() + diff)
 
     def _cursor_position_changed(self):
         """ Clears the temporary buffer based on the cursor position.
         """
         if self._text_completing_pos:
             document = self._control.document()
             if self._text_completing_pos < document.characterCount():
                 cursor = self._control.textCursor()
                 pos = cursor.position()
                 text_cursor = self._control.textCursor()
                 text_cursor.setPosition(self._text_completing_pos)
                 if pos < self._text_completing_pos or \
                         cursor.blockNumber() > text_cursor.blockNumber():
                     self._clear_temporary_buffer()
                     self._text_completing_pos = 0
             else:
                 self._clear_temporary_buffer()
                 self._text_completing_pos = 0
 
     def _custom_context_menu_requested(self, pos):
         """ Shows a context menu at the given QPoint (in widget coordinates).
         """
         menu = self._context_menu_make(pos)
         menu.exec_(self._control.mapToGlobal(pos))

IPython/frontend/qt/console/ipython_widget.py

@@ -1,559 +1,561 b''
 """ A FrontendWidget that emulates the interface of the console IPython and
     supports the additional functionality provided by the IPython kernel.
 """
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 # Standard library imports
 from collections import namedtuple
 import os.path
 import re
 from subprocess import Popen
 import sys
 import time
 from textwrap import dedent
 
 # System library imports
 from IPython.external.qt import QtCore, QtGui
 
 # Local imports
 from IPython.core.inputsplitter import IPythonInputSplitter, \
     transform_ipy_prompt
 from IPython.utils.traitlets import Bool, Unicode
 from frontend_widget import FrontendWidget
 import styles
 
 #-----------------------------------------------------------------------------
 # Constants
 #-----------------------------------------------------------------------------
 
 # Default strings to build and display input and output prompts (and separators
 # in between)
 default_in_prompt = 'In [<span class="in-prompt-number">%i</span>]: '
 default_out_prompt = 'Out[<span class="out-prompt-number">%i</span>]: '
 default_input_sep = '\n'
 default_output_sep = ''
 default_output_sep2 = ''
 
 # Base path for most payload sources.
 zmq_shell_source = 'IPython.zmq.zmqshell.ZMQInteractiveShell'
 
 if sys.platform.startswith('win'):
     default_editor = 'notepad'
 else:
     default_editor = ''
 
 #-----------------------------------------------------------------------------
 # IPythonWidget class
 #-----------------------------------------------------------------------------
 
 class IPythonWidget(FrontendWidget):
     """ A FrontendWidget for an IPython kernel.
     """
 
     # If set, the 'custom_edit_requested(str, int)' signal will be emitted when
     # an editor is needed for a file. This overrides 'editor' and 'editor_line'
     # settings.
     custom_edit = Bool(False)
     custom_edit_requested = QtCore.Signal(object, object)
 
     editor = Unicode(default_editor, config=True,
         help="""
         A command for invoking a system text editor. If the string contains a
         {filename} format specifier, it will be used. Otherwise, the filename
         will be appended to the end the command.
         """)
 
     editor_line = Unicode(config=True,
         help="""
         The editor command to use when a specific line number is requested. The
         string should contain two format specifiers: {line} and {filename}. If
         this parameter is not specified, the line number option to the %edit
         magic will be ignored.
         """)
 
     style_sheet = Unicode(config=True,
         help="""
         A CSS stylesheet. The stylesheet can contain classes for:
             1. Qt: QPlainTextEdit, QFrame, QWidget, etc
             2. Pygments: .c, .k, .o, etc. (see PygmentsHighlighter)
             3. IPython: .error, .in-prompt, .out-prompt, etc
         """)
 
     syntax_style = Unicode(config=True,
         help="""
         If not empty, use this Pygments style for syntax highlighting.
         Otherwise, the style sheet is queried for Pygments style
         information.
         """)
 
     # Prompts.
     in_prompt = Unicode(default_in_prompt, config=True)
     out_prompt = Unicode(default_out_prompt, config=True)
     input_sep = Unicode(default_input_sep, config=True)
     output_sep = Unicode(default_output_sep, config=True)
     output_sep2 = Unicode(default_output_sep2, config=True)
 
     # FrontendWidget protected class variables.
     _input_splitter_class = IPythonInputSplitter
     _transform_prompt = staticmethod(transform_ipy_prompt)
 
     # IPythonWidget protected class variables.
     _PromptBlock = namedtuple('_PromptBlock', ['block', 'length', 'number'])
     _payload_source_edit = zmq_shell_source + '.edit_magic'
     _payload_source_exit = zmq_shell_source + '.ask_exit'
     _payload_source_next_input = zmq_shell_source + '.set_next_input'
     _payload_source_page = 'IPython.zmq.page.page'
     _retrying_history_request = False
 
     #---------------------------------------------------------------------------
     # 'object' interface
     #---------------------------------------------------------------------------
 
     def __init__(self, *args, **kw):
         super(IPythonWidget, self).__init__(*args, **kw)
 
         # IPythonWidget protected variables.
         self._payload_handlers = {
             self._payload_source_edit : self._handle_payload_edit,
             self._payload_source_exit : self._handle_payload_exit,
             self._payload_source_page : self._handle_payload_page,
             self._payload_source_next_input : self._handle_payload_next_input }
         self._previous_prompt_obj = None
         self._keep_kernel_on_exit = None
 
         # Initialize widget styling.
         if self.style_sheet:
             self._style_sheet_changed()
             self._syntax_style_changed()
         else:
             self.set_default_style()
 
     #---------------------------------------------------------------------------
     # 'BaseFrontendMixin' abstract interface
     #---------------------------------------------------------------------------
 
     def _handle_complete_reply(self, rep):
         """ Reimplemented to support IPython's improved completion machinery.
         """
         self.log.debug("complete: %s", rep.get('content', ''))
         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():
             matches = rep['content']['matches']
             text = rep['content']['matched_text']
             offset = len(text)
 
             # Clean up matches with period and path separators if the matched
             # text has not been transformed. This is done by truncating all
             # but the last component and then suitably decreasing the offset
             # between the current cursor position and the start of completion.
             if len(matches) > 1 and matches[0][:offset] == text:
                 parts = re.split(r'[./\\]', text)
                 sep_count = len(parts) - 1
                 if sep_count:
                     chop_length = sum(map(len, parts[:sep_count])) + sep_count
                     matches = [ match[chop_length:] for match in matches ]
                     offset -= chop_length
 
             # Move the cursor to the start of the match and complete.
             cursor.movePosition(QtGui.QTextCursor.Left, n=offset)
             self._complete_with_items(cursor, matches)
 
     def _handle_execute_reply(self, msg):
         """ Reimplemented to support prompt requests.
         """
         msg_id = msg['parent_header'].get('msg_id')
         info = self._request_info['execute'].get(msg_id)
         if info and info.kind == 'prompt':
            number = msg['content']['execution_count'] + 1
            self._show_interpreter_prompt(number)
            self._request_info['execute'].pop(msg_id)
         else:
            super(IPythonWidget, self)._handle_execute_reply(msg)
 
     def _handle_history_reply(self, msg):
         """ Implemented to handle history tail replies, which are only supported
             by the IPython kernel.
         """
         self.log.debug("history: %s", msg.get('content', ''))
         content = msg['content']
         if 'history' not in content:
             self.log.error("History request failed: %r"%content)
             if content.get('status', '') == 'aborted' and \
                                             not self._retrying_history_request:
                 # a *different* action caused this request to be aborted, so
                 # we should try again.
                 self.log.error("Retrying aborted history request")
                 # prevent multiple retries of aborted requests:
                 self._retrying_history_request = True
                 # wait out the kernel's queue flush, which is currently timed at 0.1s
                 time.sleep(0.25)
                 self.kernel_manager.shell_channel.history(hist_access_type='tail',n=1000)
             else:
                 self._retrying_history_request = False
             return
         # reset retry flag
         self._retrying_history_request = False
         history_items = content['history']
         items = []
         last_cell = u""
         for _, _, cell in history_items:
             cell = cell.rstrip()
             if cell != last_cell:
                 items.append(cell)
                 last_cell = cell
         self._set_history(items)
 
     def _handle_pyout(self, msg):
         """ Reimplemented for IPython-style "display hook".
         """
         self.log.debug("pyout: %s", msg.get('content', ''))
         if not self._hidden and self._is_from_this_session(msg):
             content = msg['content']
             prompt_number = content['execution_count']
             data = content['data']
             if data.has_key('text/html'):
                 self._append_plain_text(self.output_sep, True)
                 self._append_html(self._make_out_prompt(prompt_number), True)
                 html = data['text/html']
                 self._append_plain_text('\n', True)
                 self._append_html(html + self.output_sep2, True)
             elif data.has_key('text/plain'):
                 self._append_plain_text(self.output_sep, True)
                 self._append_html(self._make_out_prompt(prompt_number), True)
                 text = data['text/plain']
                 # If the repr is multiline, make sure we start on a new line,
                 # so that its lines are aligned.
                 if "\n" in text and not self.output_sep.endswith("\n"):
                     self._append_plain_text('\n', True)
                 self._append_plain_text(text + self.output_sep2, True)
 
     def _handle_display_data(self, msg):
         """ The base handler for the ``display_data`` message.
         """
         self.log.debug("display: %s", msg.get('content', ''))
         # For now, we don't display data from other frontends, but we
         # eventually will as this allows all frontends to monitor the display
         # data. But we need to figure out how to handle this in the GUI.
         if not self._hidden and self._is_from_this_session(msg):
             source = msg['content']['source']
             data = msg['content']['data']
             metadata = msg['content']['metadata']
             # In the regular IPythonWidget, we simply print the plain text
             # representation.
             if data.has_key('text/html'):
                 html = data['text/html']
                 self._append_html(html, True)
             elif data.has_key('text/plain'):
                 text = data['text/plain']
                 self._append_plain_text(text, True)
             # This newline seems to be needed for text and html output.
             self._append_plain_text(u'\n', True)
 
     def _started_channels(self):
         """ Reimplemented to make a history request.
         """
         super(IPythonWidget, self)._started_channels()
         self.kernel_manager.shell_channel.history(hist_access_type='tail',
                                                   n=1000)
     #---------------------------------------------------------------------------
     # 'ConsoleWidget' public interface
     #---------------------------------------------------------------------------
 
     #---------------------------------------------------------------------------
     # 'FrontendWidget' public interface
     #---------------------------------------------------------------------------
 
     def execute_file(self, path, hidden=False):
         """ Reimplemented to use the 'run' magic.
         """
         # Use forward slashes on Windows to avoid escaping each separator.
         if sys.platform == 'win32':
             path = os.path.normpath(path).replace('\\', '/')
 
         # Perhaps we should not be using %run directly, but while we
         # are, it is necessary to quote or escape filenames containing spaces 
         # or quotes. 
         
         # In earlier code here, to minimize escaping, we sometimes quoted the 
         # filename with single quotes. But to do this, this code must be
         # platform-aware, because run uses shlex rather than python string
         # parsing, so that:
         # * In Win: single quotes can be used in the filename without quoting,
         #   and we cannot use single quotes to quote the filename.
         # * In *nix: we can escape double quotes in a double quoted filename,
         #   but can't escape single quotes in a single quoted filename.
         
         # So to keep this code non-platform-specific and simple, we now only
         # use double quotes to quote filenames, and escape when needed:
         if ' ' in path or "'" in path or '"' in path:
             path = '"%s"' % path.replace('"', '\\"')
         self.execute('%%run %s' % path, hidden=hidden)
 
     #---------------------------------------------------------------------------
     # 'FrontendWidget' protected interface
     #---------------------------------------------------------------------------
 
     def _complete(self):
         """ Reimplemented to support IPython's improved completion machinery.
         """
         # We let the kernel split the input line, so we *always* send an empty
         # text field. Readline-based frontends do get a real text field which
         # they can use.
         text = ''
 
         # Send the completion request to the kernel
         msg_id = self.kernel_manager.shell_channel.complete(
             text,                                    # 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 _process_execute_error(self, msg):
         """ Reimplemented for IPython-style traceback formatting.
         """
         content = msg['content']
         traceback = '\n'.join(content['traceback']) + '\n'
         if False:
             # FIXME: For now, tracebacks come as plain text, so we can't use
             # the html renderer yet.  Once we refactor ultratb to produce
             # properly styled tracebacks, this branch should be the default
             traceback = traceback.replace(' ', '&nbsp;')
             traceback = traceback.replace('\n', '<br/>')
 
             ename = content['ename']
             ename_styled = '<span class="error">%s</span>' % ename
             traceback = traceback.replace(ename, ename_styled)
 
             self._append_html(traceback)
         else:
             # This is the fallback for now, using plain text with ansi escapes
             self._append_plain_text(traceback)
 
     def _process_execute_payload(self, item):
         """ Reimplemented to dispatch payloads to handler methods.
         """
         handler = self._payload_handlers.get(item['source'])
         if handler is None:
             # We have no handler for this type of payload, simply ignore it
             return False
         else:
             handler(item)
             return True
 
     def _show_interpreter_prompt(self, number=None):
         """ Reimplemented for IPython-style prompts.
         """
         # If a number was not specified, make a prompt number request.
         if number is None:
             msg_id = self.kernel_manager.shell_channel.execute('', silent=True)
             info = self._ExecutionRequest(msg_id, 'prompt')
             self._request_info['execute'][msg_id] = info
             return
 
         # Show a new prompt and save information about it so that it can be
         # updated later if the prompt number turns out to be wrong.
         self._prompt_sep = self.input_sep
         self._show_prompt(self._make_in_prompt(number), html=True)
         block = self._control.document().lastBlock()
         length = len(self._prompt)
         self._previous_prompt_obj = self._PromptBlock(block, length, number)
 
         # Update continuation prompt to reflect (possibly) new prompt length.
         self._set_continuation_prompt(
             self._make_continuation_prompt(self._prompt), html=True)
 
     def _show_interpreter_prompt_for_reply(self, msg):
         """ Reimplemented for IPython-style prompts.
         """
         # Update the old prompt number if necessary.
         content = msg['content']
         # abort replies do not have any keys:
         if content['status'] == 'aborted':
             if self._previous_prompt_obj:
                 previous_prompt_number = self._previous_prompt_obj.number
             else:
                 previous_prompt_number = 0
         else:
             previous_prompt_number = content['execution_count']
         if self._previous_prompt_obj and \
                 self._previous_prompt_obj.number != previous_prompt_number:
             block = self._previous_prompt_obj.block
 
             # Make sure the prompt block has not been erased.
             if block.isValid() and block.text():
 
                 # Remove the old prompt and insert a new prompt.
                 cursor = QtGui.QTextCursor(block)
                 cursor.movePosition(QtGui.QTextCursor.Right,
                                     QtGui.QTextCursor.KeepAnchor,
                                     self._previous_prompt_obj.length)
                 prompt = self._make_in_prompt(previous_prompt_number)
                 self._prompt = self._insert_html_fetching_plain_text(
                     cursor, prompt)
 
                 # When the HTML is inserted, Qt blows away the syntax
                 # highlighting for the line, so we need to rehighlight it.
                 self._highlighter.rehighlightBlock(cursor.block())
 
             self._previous_prompt_obj = None
 
         # Show a new prompt with the kernel's estimated prompt number.
         self._show_interpreter_prompt(previous_prompt_number + 1)
 
     #---------------------------------------------------------------------------
     # 'IPythonWidget' interface
     #---------------------------------------------------------------------------
 
     def set_default_style(self, colors='lightbg'):
         """ Sets the widget style to the class defaults.
 
         Parameters:
         -----------
         colors : str, optional (default lightbg)
             Whether to use the default IPython light background or dark
             background or B&W style.
         """
         colors = colors.lower()
         if colors=='lightbg':
             self.style_sheet = styles.default_light_style_sheet
             self.syntax_style = styles.default_light_syntax_style
         elif colors=='linux':
             self.style_sheet = styles.default_dark_style_sheet
             self.syntax_style = styles.default_dark_syntax_style
         elif colors=='nocolor':
             self.style_sheet = styles.default_bw_style_sheet
             self.syntax_style = styles.default_bw_syntax_style
         else:
             raise KeyError("No such color scheme: %s"%colors)
 
     #---------------------------------------------------------------------------
     # 'IPythonWidget' protected interface
     #---------------------------------------------------------------------------
 
     def _edit(self, filename, line=None):
         """ Opens a Python script for editing.
 
         Parameters:
         -----------
         filename : str
             A path to a local system file.
 
         line : int, optional
             A line of interest in the file.
         """
         if self.custom_edit:
             self.custom_edit_requested.emit(filename, line)
         elif not self.editor:
             self._append_plain_text('No default editor available.\n'
             'Specify a GUI text editor in the `IPythonWidget.editor` '
             'configurable to enable the %edit magic')
         else:
             try:
                 filename = '"%s"' % filename
                 if line and self.editor_line:
                     command = self.editor_line.format(filename=filename,
                                                       line=line)
                 else:
                     try:
                         command = self.editor.format()
                     except KeyError:
                         command = self.editor.format(filename=filename)
                     else:
                         command += ' ' + filename
             except KeyError:
                 self._append_plain_text('Invalid editor command.\n')
             else:
                 try:
                     Popen(command, shell=True)
                 except OSError:
                     msg = 'Opening editor with command "%s" failed.\n'
                     self._append_plain_text(msg % command)
 
     def _make_in_prompt(self, number):
         """ Given a prompt number, returns an HTML In prompt.
         """
         try:
             body = self.in_prompt % number
         except TypeError:
             # allow in_prompt to leave out number, e.g. '>>> '
             body = self.in_prompt
         return '<span class="in-prompt">%s</span>' % body
 
     def _make_continuation_prompt(self, prompt):
         """ Given a plain text version of an In prompt, returns an HTML
             continuation prompt.
         """
         end_chars = '...: '
         space_count = len(prompt.lstrip('\n')) - len(end_chars)
         body = '&nbsp;' * space_count + end_chars
         return '<span class="in-prompt">%s</span>' % body
 
     def _make_out_prompt(self, number):
         """ Given a prompt number, returns an HTML Out prompt.
         """
         body = self.out_prompt % number
         return '<span class="out-prompt">%s</span>' % body
 
     #------ Payload handlers --------------------------------------------------
 
     # Payload handlers with a generic interface: each takes the opaque payload
     # dict, unpacks it and calls the underlying functions with the necessary
     # arguments.
 
     def _handle_payload_edit(self, item):
         self._edit(item['filename'], item['line_number'])
 
     def _handle_payload_exit(self, item):
         self._keep_kernel_on_exit = item['keepkernel']
         self.exit_requested.emit(self)
 
     def _handle_payload_next_input(self, item):
         self.input_buffer = dedent(item['text'].rstrip())
 
     def _handle_payload_page(self, item):
         # Since the plain text widget supports only a very small subset of HTML
         # and we have no control over the HTML source, we only page HTML
         # payloads in the rich text widget.
         if item['html'] and self.kind == 'rich':
             self._page(item['html'], html=True)
         else:
             self._page(item['text'], html=False)
 
     #------ Trait change handlers --------------------------------------------
 
     def _style_sheet_changed(self):
         """ Set the style sheets of the underlying widgets.
         """
         self.setStyleSheet(self.style_sheet)
+        if self._control is not None:
         self._control.document().setDefaultStyleSheet(self.style_sheet)
-        if self._page_control:
-            self._page_control.document().setDefaultStyleSheet(self.style_sheet)
-
         bg_color = self._control.palette().window().color()
         self._ansi_processor.set_background_color(bg_color)
 
+        if self._page_control is not None:
+            self._page_control.document().setDefaultStyleSheet(self.style_sheet)
+
+
 
     def _syntax_style_changed(self):
         """ Set the style for the syntax highlighter.
         """
         if self._highlighter is None:
             # ignore premature calls
             return
         if self.syntax_style:
             self._highlighter.set_style(self.syntax_style)
         else:
             self._highlighter.set_style_sheet(self.style_sheet)
 
     #------ Trait default initializers -----------------------------------------
 
     def _banner_default(self):
         from IPython.core.usage import default_gui_banner
         return default_gui_banner