Do not generate output for empty figures in Qt console.

Before, calling figure() would produce a big blank area.  This ensures
output is only returned if the figure has content.

Also added basic testing for pylabtools, for which we had none.

IPython/lib/pylabtools.py

@@ -77,6 +77,11 b' def figsize(sizex, sizey):'
 
 def figure_to_svg(fig):
     """Convert a figure to svg for inline display."""
+    # When there's an empty figure, we shouldn't return anything, otherwise we
+    # get big blank areas in the qt console.
+    if not fig.axes:
+        return
+
     fc = fig.get_facecolor()
     ec = fig.get_edgecolor()
     fig.set_facecolor('white')
@@ -240,7 +245,6 b' def import_pylab(user_ns, backend, import_all=True, shell=None):'
         
         # The old pastefig function has been replaced by display
         # Always add this svg formatter so display works.
-        from IPython.zmq.pylab.backend_inline import figure_to_svg
         from IPython.core.display import display, display_svg
         svg_formatter = shell.display_formatter.formatters['image/svg+xml']
         svg_formatter.for_type_by_name(

IPython/testing/iptest.py

@@ -101,11 +101,12 b' def test_for(mod, min_version=None):'
 have = {}
 
 have['curses'] = test_for('_curses')
+have['matplotlib'] = test_for('matplotlib')
+have['pexpect'] = test_for('pexpect')
+have['pymongo'] = test_for('pymongo')
 have['wx'] = test_for('wx')
 have['wx.aui'] = test_for('wx.aui')
-have['pexpect'] = test_for('pexpect')
 have['zmq'] = test_for('zmq', '2.1.4')
-have['pymongo'] = test_for('pymongo')
 
 #-----------------------------------------------------------------------------
 # Functions and classes
@@ -191,6 +192,11 b' def make_exclude():'
     if not have['pymongo']:
         exclusions.append(ipjoin('parallel', 'controller', 'mongodb'))
 
+    if not have['matplotlib']:
+        exclusions.extend([ipjoin('lib', 'pylabtools'),
+                           ipjoin('lib', 'pylabtools',
+                                  'tests', 'test_pylabtools')])
+
     # This is needed for the reg-exp to match on win32 in the ipdoctest plugin.
     if sys.platform == 'win32':
         exclusions = [s.replace('\\','\\\\') for s in exclusions]

IPython/zmq/pylab/backend_inline.py

@@ -6,7 +6,9 b''
 from __future__ import print_function
 
 # Standard library imports
+import sys
 
+# Third-party imports
 import matplotlib
 from matplotlib.backends.backend_svg import new_figure_manager
 from matplotlib._pylab_helpers import Gcf
@@ -64,7 +66,15 b' def flush_svg():'
 def send_svg_figure(fig):
     """Draw the current figure and send it as an SVG payload.
     """
+    # For an empty figure, don't even bother calling figure_to_svg, to avoid
+    # big blank spaces in the qt console
+    if not fig.axes:
+        return
+
     svg = figure_to_svg(fig)
+    # flush text streams before sending figures, helps a little with output
+    # synchronization in the console (though it's a bandaid, not a real sln)
+    sys.stdout.flush(); sys.stderr.flush()
     publish_display_data(
         'IPython.zmq.pylab.backend_inline.send_svg_figure',
         'Matplotlib Plot',