Make inline the default matplotlib backend

docs/changelog.rst

@@ -1,6 +1,21 @@
 Changes in IPython kernel
 =========================
 
+4.4
+---
+
+4.4.0
+*****
+
+`4.4.0 on GitHub <https://github.com/ipython/ipykernel/milestones/4.4>`__
+
+- Use `MPLBACKEND`_ environment variable to tell matplotlib >= 1.5 use use the inline backend by default.
+  This is only done if MPLBACKEND is not already set and no backend has been explicitly loaded,
+  so setting ``MPLBACKEND=Qt4Agg`` or calling ``%matplotlib notebook`` or ``matplotlib.use('Agg')``
+  will take precedence.
+
+.. _MPLBACKEND: http://matplotlib.org/devel/coding_guide.html?highlight=mplbackend#developing-a-new-backend
+
 4.3
 ---
 

ipykernel/kernelapp.py

@@ -368,6 +368,13 @@ def init_kernel(self):
     def init_gui_pylab(self):
         """Enable GUI event loop integration, taking pylab into account."""
 
+        # Register inline backend as default
+        # this is higher priority than matplotlibrc,
+        # but lower priority than anything else (mpl.use() for instance).
+        # This only affects matplotlib >= 1.5
+        if not os.environ.get('MPLBACKEND'):
+            os.environ['MPLBACKEND'] = 'module://ipykernel.pylab.backend_inline'
+
         # Provide a wrapper for :meth:`InteractiveShellApp.init_gui_pylab`
         # to ensure that any exception is printed straight to stderr.
         # Normally _showtraceback associates the reply with an execution,

ipykernel/pylab/backend_inline.py

@@ -143,3 +143,14 @@ def flush_figures():
 # figurecanvas. This is set here to a Agg canvas
 # See https://github.com/matplotlib/matplotlib/pull/1125
 FigureCanvas = FigureCanvasAgg
+
+def _enable_matplotlib_integration():
+    """Enable extra IPython matplotlib integration when we are loaded as the matplotlib backend."""
+    from matplotlib import get_backend
+    from IPython.core.pylabtools import configure_inline_support
+    ip = get_ipython()
+    backend = get_backend()
+    if ip and backend == 'module://%s' % __name__:
+        configure_inline_support(ip, backend)
+
+_enable_matplotlib_integration()