First cut at support readline-esque history filtering in ConsoleWidget.

IPython/frontend/qt/console/history_console_widget.py

@@ -7,7 +7,7 b' from console_widget import ConsoleWidget'
 
 class HistoryConsoleWidget(ConsoleWidget):
     """ A ConsoleWidget that keeps a history of the commands that have been
-        executed.
+        executed and provides a readline-esque interface to this history.
     """
     
     #---------------------------------------------------------------------------
@@ -16,8 +16,11 b' class HistoryConsoleWidget(ConsoleWidget):'
 
     def __init__(self, *args, **kw):
         super(HistoryConsoleWidget, self).__init__(*args, **kw)
+
+        # HistoryConsoleWidget protected variables.
         self._history = []
         self._history_index = 0
+        self._history_prefix = ''
 
     #---------------------------------------------------------------------------
     # 'ConsoleWidget' public interface
@@ -54,14 +57,31 b' class HistoryConsoleWidget(ConsoleWidget):'
         """
         prompt_cursor = self._get_prompt_cursor()
         if self._get_cursor().blockNumber() == prompt_cursor.blockNumber():
-            self.history_previous()
 
-            # Go to the first line of prompt for seemless history scrolling.
+            # Set a search prefix based on the cursor position.
+            col = self._get_input_buffer_cursor_column()
+            input_buffer = self.input_buffer
+            if self._history_index == len(self._history) or \
+                    (self._history_prefix and col != len(self._history_prefix)):
+                self._history_index = len(self._history)
+                self._history_prefix = input_buffer[:col]
+
+            # Perform the search.
+            self.history_previous(self._history_prefix)
+
+            # Go to the first line of the prompt for seemless history scrolling.
+            # Emulate readline: keep the cursor position fixed for a prefix
+            # search.
             cursor = self._get_prompt_cursor()
-            cursor.movePosition(QtGui.QTextCursor.EndOfLine)
+            if self._history_prefix:
+                cursor.movePosition(QtGui.QTextCursor.Right, 
+                                    n=len(self._history_prefix))
+            else:
+                cursor.movePosition(QtGui.QTextCursor.EndOfLine)
             self._set_cursor(cursor)
 
             return False
+
         return True
 
     def _down_pressed(self):
@@ -70,38 +90,69 b' class HistoryConsoleWidget(ConsoleWidget):'
         """
         end_cursor = self._get_end_cursor()
         if self._get_cursor().blockNumber() == end_cursor.blockNumber():
-            self.history_next()
+
+            # Perform the search.
+            self.history_next(self._history_prefix)
+
+            # Emulate readline: keep the cursor position fixed for a prefix
+            # search. (We don't need to move the cursor to the end of the buffer
+            # in the other case because this happens automatically when the
+            # input buffer is set.)
+            if self._history_prefix:
+                cursor = self._get_prompt_cursor()
+                cursor.movePosition(QtGui.QTextCursor.Right, 
+                                    n=len(self._history_prefix))
+                self._set_cursor(cursor)
+
             return False
+
         return True
 
     #---------------------------------------------------------------------------
     # 'HistoryConsoleWidget' public interface
     #---------------------------------------------------------------------------
 
-    def history_previous(self):
-        """ If possible, set the input buffer to the previous item in the
-            history.
-        """
-        if self._history_index > 0:
-            self._history_index -= 1
-            self.input_buffer = self._history[self._history_index]
+    def history_previous(self, prefix=''):
+        """ If possible, set the input buffer to a previous item in the history.
 
-    def history_next(self):
-        """ Set the input buffer to the next item in the history, or a blank
-            line if there is no subsequent item.
+        Parameters:
+        -----------
+        prefix : str, optional
+            If specified, search for an item with this prefix.
         """
-        if self._history_index < len(self._history):
+        index = self._history_index
+        while index > 0:
+            index -= 1
+            history = self._history[index]
+            if history.startswith(prefix):
+                break
+        else:
+            history = None
+
+        if history is not None:
+            self._history_index = index
+            self.input_buffer = history
+
+    def history_next(self, prefix=''):
+        """ Set the input buffer to a subsequent item in the history, or to the
+        original search prefix if there is no such item.
+
+        Parameters:
+        -----------
+        prefix : str, optional
+            If specified, search for an item with this prefix.
+        """
+        while self._history_index < len(self._history) - 1:
             self._history_index += 1
-            if self._history_index < len(self._history):
-                self.input_buffer = self._history[self._history_index]
-            else:
-                self.input_buffer = ''
-
-    #---------------------------------------------------------------------------
-    # 'HistoryConsoleWidget' protected interface
-    #---------------------------------------------------------------------------
+            history = self._history[self._history_index]
+            if history.startswith(prefix):
+                break
+        else:
+            self._history_index = len(self._history)
+            history = prefix
+        self.input_buffer = history
 
-    def _set_history(self, history):
+    def set_history(self, history):
         """ Replace the current history with a sequence of history items.
         """
         self._history = list(history)