* Created an IPythonWidget subclass of FrontendWidget to contain IPython specific functionality.

* Added API for overriding magic commands to the above widget.
* Added a non-zero epsilon to time.sleep in the flush method of the kernel manager per Fernando's suggestion

IPython/frontend/qt/console/ipython_widget.py

@@ -0,0 +1,80 b''
+# Local imports.
+from frontend_widget import FrontendWidget
+
+
+class IPythonWidget(FrontendWidget):
+    """ A FrontendWidget for an IPython kernel.
+    """
+
+    #---------------------------------------------------------------------------
+    # 'FrontendWidget' interface
+    #---------------------------------------------------------------------------
+    
+    def __init__(self, kernel_manager, parent=None):
+        super(IPythonWidget, self).__init__(kernel_manager, parent)
+
+        self._magic_overrides = {}
+
+    def execute_source(self, source, hidden=False, interactive=False):
+        """ Reimplemented to override magic commands.
+        """
+        magic_source = source.strip()
+        if magic_source.startswith('%'):
+            magic_source = magic_source[1:]
+        magic, sep, arguments = magic_source.partition(' ')
+        if not magic:
+            magic = magic_source
+
+        callback = self._magic_overrides.get(magic)
+        if callback:
+            output = callback(arguments)
+            if output:
+                self.appendPlainText(output)
+            self._show_prompt('>>> ')
+            return True
+        else:
+            return super(IPythonWidget, self).execute_source(source, hidden,
+                                                             interactive)
+
+    #---------------------------------------------------------------------------
+    # 'IPythonWidget' interface
+    #---------------------------------------------------------------------------
+
+    def set_magic_override(self, magic, callback):
+        """ Overrides an IPython magic command. This magic will be intercepted
+            by the frontend rather than passed on to the kernel and 'callback'
+            will be called with a single argument: a string of argument(s) for
+            the magic. The callback can (optionally) return text to print to the
+            console.
+        """
+        self._magic_overrides[magic] = callback
+
+    def remove_magic_override(self, magic):
+        """ Removes the override for the specified magic, if there is one.
+        """
+        try:
+            del self._magic_overrides[magic]
+        except KeyError:
+            pass
+
+
+if __name__ == '__main__':
+    import sys
+    from IPython.frontend.qt.kernelmanager import QtKernelManager
+
+    # Create KernelManager
+    xreq_addr = ('127.0.0.1', 5575)
+    sub_addr = ('127.0.0.1', 5576)
+    rep_addr = ('127.0.0.1', 5577)
+    kernel_manager = QtKernelManager(xreq_addr, sub_addr, rep_addr)
+    kernel_manager.sub_channel.start()
+    kernel_manager.xreq_channel.start()
+
+    # Launch application
+    app = QtGui.QApplication(sys.argv)
+    widget = IPythonWidget(kernel_manager)
+    widget.setWindowTitle('Python')
+    widget.resize(640, 480)
+    widget.show()
+    sys.exit(app.exec_())
+    

IPython/frontend/qt/console/frontend_widget.py

@@ -47,7 +47,7 b' class FrontendHighlighter(PygmentsHighlighter):'
 
 
 class FrontendWidget(HistoryConsoleWidget):
-    """ A Qt frontend for an IPython kernel.
+    """ A Qt frontend for a generic Python kernel.
     """
 
     # Emitted when an 'execute_reply' is received from the kernel.
@@ -63,7 +63,7 b' class FrontendWidget(HistoryConsoleWidget):'
         self._call_tip_widget = CallTipWidget(self)
         self._compile = CommandCompiler()
         self._completion_lexer = CompletionLexer(PythonLexer())
-        self._hidden = False
+        self._hidden = True
         self._highlighter = FrontendHighlighter(self)
         self._kernel_manager = None
 
@@ -127,6 +127,7 b' class FrontendWidget(HistoryConsoleWidget):'
             shown. Returns whether the source executed (i.e., returns True only
             if no more input is necessary).
         """
+        # Use CommandCompiler to determine if more input is needed.
         try:
             code = self._compile(source, symbol='single')
         except (OverflowError, SyntaxError, ValueError):
@@ -281,7 +282,7 b' class FrontendWidget(HistoryConsoleWidget):'
         elif status == 'aborted':
             text = "ERROR: ABORTED\n"
             self.appendPlainText(text)
-        self._hidden = False
+        self._hidden = True
         self._show_prompt('>>> ')
         self.executed.emit(rep)
 
@@ -300,25 +301,3 b' class FrontendWidget(HistoryConsoleWidget):'
             doc = rep['content']['docstring']
             if doc:
                 self._call_tip_widget.show_tip(doc)
-
-
-if __name__ == '__main__':
-    import sys
-    from IPython.frontend.qt.kernelmanager import QtKernelManager
-
-    # Create KernelManager
-    xreq_addr = ('127.0.0.1', 5575)
-    sub_addr = ('127.0.0.1', 5576)
-    rep_addr = ('127.0.0.1', 5577)
-    kernel_manager = QtKernelManager(xreq_addr, sub_addr, rep_addr)
-    kernel_manager.sub_channel.start()
-    kernel_manager.xreq_channel.start()
-
-    # Launch application
-    app = QtGui.QApplication(sys.argv)
-    widget = FrontendWidget(kernel_manager)
-    widget.setWindowTitle('Python')
-    widget.resize(640, 480)
-    widget.show()
-    sys.exit(app.exec_())
-    

IPython/zmq/kernelmanager.py

@@ -118,7 +118,7 b' class SubSocketChannel(ZmqSocketChannel):'
         self._flushed = False
         self.ioloop.add_callback(self._flush)
         while not self._flushed:
-            time.sleep(0)
+            time.sleep(0.01)
         
     def _flush(self):
         """Called in this thread by the IOLoop to indicate that all events have