First cut at a generic bracket matcher for Q[Plain]TextEdits.

IPython/frontend/qt/console/bracket_matcher.py

@@ -0,0 +1,101 b''
+""" Provides bracket matching for Q[Plain]TextEdit widgets.
+"""
+
+# System library imports
+from PyQt4 import QtCore, QtGui
+
+
+class BracketMatcher(QtCore.QObject):
+    """ Matches square brackets, braces, and parentheses based on cursor
+        position.
+    """
+    
+    # Protected class variables.
+    _opening_map = { '(':')', '{':'}', '[':']' }
+    _closing_map = { ')':'(', '}':'{', ']':'[' }
+
+    #--------------------------------------------------------------------------
+    # 'QObject' interface
+    #--------------------------------------------------------------------------
+
+    def __init__(self, parent, multiline=True):
+        """ Create a call tip manager that is attached to the specified Qt
+            text edit widget.
+        """
+        assert isinstance(parent, (QtGui.QTextEdit, QtGui.QPlainTextEdit))
+        QtCore.QObject.__init__(self, parent)
+
+        # The format to apply to matching brackets.
+        self.format = QtGui.QTextCharFormat()
+        self.format.setBackground(QtGui.QColor('silver'))
+
+        parent.cursorPositionChanged.connect(self._cursor_position_changed)
+
+    #--------------------------------------------------------------------------
+    # Protected interface
+    #--------------------------------------------------------------------------
+
+    def _find_match(self, position):
+        """ Given a valid position in the text document, try to find the
+            position of the matching bracket. Returns -1 if unsuccessful.
+        """
+        # Decide what character to search for and what direction to search in.
+        document = self.parent().document()
+        qchar = document.characterAt(position)
+        start_char = qchar.toAscii()
+        search_char = self._opening_map.get(start_char)
+        if search_char:
+            increment = 1
+        else:
+            search_char = self._closing_map.get(start_char)
+            if search_char:
+                increment = -1
+            else:
+                return -1
+
+        # Search for the character.
+        depth = 0
+        while position >= 0 and position < document.characterCount():
+            char = qchar.toAscii()
+            if char == start_char:
+                depth += 1
+            elif char == search_char:
+                depth -= 1
+            if depth == 0:
+                break
+            position += increment
+            qchar = document.characterAt(position)
+        else:
+            position = -1
+        return position
+
+    def _selection_for_character(self, position):
+        """ Convenience method for selecting a character.
+        """
+        selection = QtGui.QTextEdit.ExtraSelection()
+        cursor = self.parent().textCursor()
+        cursor.setPosition(position)
+        cursor.movePosition(QtGui.QTextCursor.NextCharacter, 
+                            QtGui.QTextCursor.KeepAnchor)
+        selection.cursor = cursor
+        selection.format = self.format
+        return selection
+
+    #------ Signal handlers ----------------------------------------------------
+
+    def _cursor_position_changed(self):
+        """ Updates the document formatting based on the new cursor position.
+        """
+        # Clear out the old formatting.
+        text_edit = self.parent()
+        text_edit.setExtraSelections([])
+
+        # Attempt to match a bracket for the new cursor position.
+        cursor = text_edit.textCursor()
+        if not cursor.hasSelection():
+            position = cursor.position() - 1
+            match_position = self._find_match(position)
+            if match_position != -1:
+                extra_selections = [ self._selection_for_character(pos)
+                                     for pos in (position, match_position) ]
+                text_edit.setExtraSelections(extra_selections)

IPython/frontend/qt/console/frontend_widget.py

@@ -9,7 +9,8 b' from PyQt4 import QtCore, QtGui'
 # Local imports
 from IPython.core.inputsplitter import InputSplitter
 from IPython.frontend.qt.base_frontend_mixin import BaseFrontendMixin
-from IPython.utils.traitlets import Bool, Type
+from IPython.utils.traitlets import Bool
+from bracket_matcher import BracketMatcher
 from call_tip_widget import CallTipWidget
 from completion_lexer import CompletionLexer
 from console_widget import HistoryConsoleWidget
@@ -88,8 +89,7 b' class FrontendWidget(HistoryConsoleWidget, BaseFrontendMixin):'
     executed = QtCore.pyqtSignal(object)
     
     # Protected class variables.
-    _highlighter_class = Type(FrontendHighlighter)
-    _input_splitter_class = Type(InputSplitter)
+    _input_splitter_class = InputSplitter
 
     #---------------------------------------------------------------------------
     # 'object' interface
@@ -99,10 +99,11 b' class FrontendWidget(HistoryConsoleWidget, BaseFrontendMixin):'
         super(FrontendWidget, self).__init__(*args, **kw)
 
         # FrontendWidget protected variables.
+        self._bracket_matcher = BracketMatcher(self._control)
         self._call_tip_widget = CallTipWidget(self._control)
         self._completion_lexer = CompletionLexer(PythonLexer())
         self._hidden = False
-        self._highlighter = self._highlighter_class(self)
+        self._highlighter = FrontendHighlighter(self)
         self._input_splitter = self._input_splitter_class(input_mode='block')
         self._kernel_manager = None
 

IPython/frontend/qt/console/pygments_highlighter.py

@@ -110,14 +110,12 b' class PygmentsHighlighter(QtGui.QSyntaxHighlighter):'
         elif hasattr(self._lexer, '_saved_state_stack'):
             del self._lexer._saved_state_stack
 
-        index = 0
         # Lex the text using Pygments
+        index = 0
         for token, text in self._lexer.get_tokens(qstring):
-            l = len(text)
-            format = self._get_format(token)
-            if format is not None:
-                self.setFormat(index, l, format)
-            index += l
+            length = len(text)
+            self.setFormat(index, length, self._get_format(token))
+            index += length
 
         if hasattr(self._lexer, '_saved_state_stack'):
             data = PygmentsBlockUserData(
@@ -185,11 +183,9 b' class PygmentsHighlighter(QtGui.QSyntaxHighlighter):'
     def _get_format_from_style(self, token, style):
         """ Returns a QTextCharFormat for token by reading a Pygments style.
         """
-        result = None
+        result = QtGui.QTextCharFormat()
         for key, value in style.style_for_token(token).items():
             if value:
-                if result is None:
-                    result = QtGui.QTextCharFormat()
                 if key == 'color':
                     result.setForeground(self._get_brush(value))
                 elif key == 'bgcolor':