Improved matplotlib backend and plotting.

* Set background to white. I tried transparent, but white looked
  better.
* Fixed dark style sheet for rich text widget.

IPython/frontend/qt/console/ipython_widget.py

@@ -198,7 +198,7 b' class IPythonWidget(FrontendWidget):'
         """ Restores the default IPythonWidget styling.
         """
         self.set_styling(self.default_stylesheet, syntax_style='default')
-        #self.set_styling(self.dark_stylesheet, syntax_style='monokai')
+        # self.set_styling(self.dark_stylesheet, syntax_style='monokai')
 
     def set_editor(self, editor):
         """ Sets the editor to use with the %edit magic.

IPython/frontend/qt/console/rich_ipython_widget.py

@@ -15,6 +15,17 b' class RichIPythonWidget(IPythonWidget):'
     # Protected class variables.
     _svg_text_format_property = 1
 
+    # We need to override this because this class uses QTextEdit.
+    dark_stylesheet = """
+        QTextEdit { background-color: black; color: white }
+        QFrame { border: 1px solid grey; }
+        .error { color: red; }
+        .in-prompt { color: lime; }
+        .in-prompt-number { color: lime; font-weight: bold; }
+        .out-prompt { color: red; }
+        .out-prompt-number { color: red; font-weight: bold; }
+    """
+
     #---------------------------------------------------------------------------
     # 'object' interface
     #---------------------------------------------------------------------------

IPython/zmq/pylab/backend_payload_svg.py

@@ -14,6 +14,11 b' def show():'
     """
     figure_manager = Gcf.get_active()
     if figure_manager is not None:
+        # Make the background transparent.
+        # figure_manager.canvas.figure.patch.set_alpha(0.0)
+        # Set the background to white instead so it looks good on black.
+        figure_manager.canvas.figure.set_facecolor('white')
+        figure_manager.canvas.figure.set_edgecolor('white')
         data = svg_from_canvas(figure_manager.canvas)
         add_plot_payload('svg', data)