Improve Qt console's placement of text appended before a prompt.

IPython/frontend/qt/console/console_widget.py

@@ -195,6 +195,7 b' class ConsoleWidget(Configurable, QtGui.QWidget):'
 
         # 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 = '> '
@@ -727,8 +728,7 b' class ConsoleWidget(Configurable, QtGui.QWidget):'
         # Determine where to insert the content.
         cursor = self._control.textCursor()
         if before_prompt and not self._executing:
-            cursor.setPosition(self._prompt_pos)
-            cursor.movePosition(QtGui.QTextCursor.Left, n=len(self._prompt))
+            cursor.setPosition(self._append_before_prompt_pos)
         else:
             cursor.movePosition(QtGui.QTextCursor.End)
         start_pos = cursor.position()
@@ -739,7 +739,9 b' class ConsoleWidget(Configurable, QtGui.QWidget):'
         # 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:
-            self._prompt_pos += cursor.position() - start_pos
+            diff = cursor.position() - start_pos
+            self._append_before_prompt_pos += diff
+            self._prompt_pos += diff
             
         return result
 
@@ -1726,10 +1728,12 b' class ConsoleWidget(Configurable, QtGui.QWidget):'
             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.
         """
-        # Insert a preliminary newline, if necessary.
-        if newline:
+        # Save the current end position to support _append*(before_prompt=True).
             cursor = self._get_end_cursor()
-            if cursor.position() > 0:
+        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':

IPython/frontend/qt/console/frontend_widget.py

@@ -22,8 +22,7 b' from pygments_highlighter import PygmentsHighlighter'
 
 
 class FrontendHighlighter(PygmentsHighlighter):
-    """ A PygmentsHighlighter that can be turned on and off and that ignores
-        prompts.
+    """ A PygmentsHighlighter that understands and ignores prompts.
     """
 
     def __init__(self, frontend):
@@ -50,14 +49,12 b' class FrontendHighlighter(PygmentsHighlighter):'
         else:
             prompt = self._frontend._continuation_prompt
 
-        # Don't highlight the part of the string that contains the prompt.
+        # Only highlight if we can identify a prompt, but make sure not to
+        # highlight the prompt.
         if string.startswith(prompt):
             self._current_offset = len(prompt)
             string = string[len(prompt):]
-        else:
-            self._current_offset = 0
-
-        PygmentsHighlighter.highlightBlock(self, string)
+            super(FrontendHighlighter, self).highlightBlock(string)
 
     def rehighlightBlock(self, block):
         """ Reimplemented to temporarily enable highlighting if disabled.
@@ -71,7 +68,7 b' class FrontendHighlighter(PygmentsHighlighter):'
         """ Reimplemented to highlight selectively.
         """
         start += self._current_offset
-        PygmentsHighlighter.setFormat(self, start, count, format)
+        super(FrontendHighlighter, self).setFormat(start, count, format)
 
 
 class FrontendWidget(HistoryConsoleWidget, BaseFrontendMixin):