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

@@ -1,295 +1,299
 # -*- coding: utf-8 -*-
 """Pylab (matplotlib) support utilities.
 
 Authors
 -------
 
 * Fernando Perez.
 * Brian Granger
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2009  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 from cStringIO import StringIO
 
 from IPython.utils.decorators import flag_calls
 
 # If user specifies a GUI, that dictates the backend, otherwise we read the
 # user's mpl default from the mpl rc structure
 backends = {'tk': 'TkAgg',
             'gtk': 'GTKAgg',
             'wx': 'WXAgg',
             'qt': 'Qt4Agg', # qt3 not supported
             'qt4': 'Qt4Agg',
             'osx': 'MacOSX',
             'inline' : 'module://IPython.zmq.pylab.backend_inline'}
 
 #-----------------------------------------------------------------------------
 # Matplotlib utilities
 #-----------------------------------------------------------------------------
 
 
 def getfigs(*fig_nums):
     """Get a list of matplotlib figures by figure numbers.
 
     If no arguments are given, all available figures are returned.  If the
     argument list contains references to invalid figures, a warning is printed
     but the function continues pasting further figures.
 
     Parameters
     ----------
     figs : tuple
         A tuple of ints giving the figure numbers of the figures to return.
     """
     from matplotlib._pylab_helpers import Gcf
     if not fig_nums:
         fig_managers = Gcf.get_all_fig_managers()
         return [fm.canvas.figure for fm in fig_managers]
     else:
         figs = []
         for num in fig_nums:
             f = Gcf.figs.get(num)
             if f is None:
                 print('Warning: figure %s not available.' % num)
             figs.append(f.canvas.figure)
         return figs
 
 
 def figsize(sizex, sizey):
     """Set the default figure size to be [sizex, sizey].
 
     This is just an easy to remember, convenience wrapper that sets::
 
       matplotlib.rcParams['figure.figsize'] = [sizex, sizey]
     """
     import matplotlib
     matplotlib.rcParams['figure.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')
     fig.set_edgecolor('white')
     try:
         string_io = StringIO()
         fig.canvas.print_figure(string_io, format='svg')
         svg = string_io.getvalue()
     finally:
         fig.set_facecolor(fc)
         fig.set_edgecolor(ec)
     return svg
 
 
 # We need a little factory function here to create the closure where
 # safe_execfile can live.
 def mpl_runner(safe_execfile):
     """Factory to return a matplotlib-enabled runner for %run.
 
     Parameters
     ----------
     safe_execfile : function
       This must be a function with the same interface as the
       :meth:`safe_execfile` method of IPython.
 
     Returns
     -------
     A function suitable for use as the ``runner`` argument of the %run magic
     function.
     """
     
     def mpl_execfile(fname,*where,**kw):
         """matplotlib-aware wrapper around safe_execfile.
 
         Its interface is identical to that of the :func:`execfile` builtin.
 
         This is ultimately a call to execfile(), but wrapped in safeties to
         properly handle interactive rendering."""
 
         import matplotlib
         import matplotlib.pylab as pylab
 
         #print '*** Matplotlib runner ***' # dbg
         # turn off rendering until end of script
         is_interactive = matplotlib.rcParams['interactive']
         matplotlib.interactive(False)
         safe_execfile(fname,*where,**kw)
         matplotlib.interactive(is_interactive)
         # make rendering call now, if the user tried to do it
         if pylab.draw_if_interactive.called:
             pylab.draw()
             pylab.draw_if_interactive.called = False
 
     return mpl_execfile
 
 
 #-----------------------------------------------------------------------------
 # Code for initializing matplotlib and importing pylab
 #-----------------------------------------------------------------------------
 
 
 def find_gui_and_backend(gui=None):
     """Given a gui string return the gui and mpl backend.
 
     Parameters
     ----------
     gui : str
         Can be one of ('tk','gtk','wx','qt','qt4','inline').
 
     Returns
     -------
     A tuple of (gui, backend) where backend is one of ('TkAgg','GTKAgg',
     'WXAgg','Qt4Agg','module://IPython.zmq.pylab.backend_inline').
     """
 
     import matplotlib
 
     if gui:
         # select backend based on requested gui
         backend = backends[gui]
     else:
         backend = matplotlib.rcParams['backend']
         # In this case, we need to find what the appropriate gui selection call
         # should be for IPython, so we can activate inputhook accordingly
         g2b = backends  # maps gui names to mpl backend names
         b2g = dict(zip(g2b.values(), g2b.keys()))  # reverse dict
         gui = b2g.get(backend, None)
     return gui, backend
 
 
 def activate_matplotlib(backend):
     """Activate the given backend and set interactive to True."""
 
     import matplotlib
     if backend.startswith('module://'):
         # Work around bug in matplotlib: matplotlib.use converts the
         # backend_id to lowercase even if a module name is specified!
         matplotlib.rcParams['backend'] = backend
     else:
         matplotlib.use(backend)
     matplotlib.interactive(True)
 
     # This must be imported last in the matplotlib series, after
     # backend/interactivity choices have been made
     import matplotlib.pylab as pylab
 
     # XXX For now leave this commented out, but depending on discussions with
     # mpl-dev, we may be able to allow interactive switching...
     #import matplotlib.pyplot
     #matplotlib.pyplot.switch_backend(backend)
 
     pylab.show._needmain = False
     # We need to detect at runtime whether show() is called by the user.
     # For this, we wrap it into a decorator which adds a 'called' flag.
     pylab.draw_if_interactive = flag_calls(pylab.draw_if_interactive)
 
 
 def import_pylab(user_ns, backend, import_all=True, shell=None):
     """Import the standard pylab symbols into user_ns."""
 
     # Import numpy as np/pyplot as plt are conventions we're trying to
     # somewhat standardize on.  Making them available to users by default
     # will greatly help this.
     s = ("import numpy\n"
           "import matplotlib\n"
           "from matplotlib import pylab, mlab, pyplot\n"
           "np = numpy\n"
           "plt = pyplot\n"
           )
     exec s in user_ns
 
     if shell is not None:
         exec s in shell.user_ns_hidden
         # If using our svg payload backend, register the post-execution
         # function that will pick up the results for display.  This can only be
         # done with access to the real shell object.
         if backend == backends['inline']:
             from IPython.zmq.pylab.backend_inline import flush_svg
             from matplotlib import pyplot
             shell.register_post_execute(flush_svg)
             # The typical default figure size is too large for inline use,
             # so we shrink the figure size to 6x4, and tweak fonts to
             # make that fit.  This is configurable via Global.pylab_inline_rc,
             # or rather it will be once the zmq kernel is hooked up to
             # the config system.
             
             default_rc = {
                 'figure.figsize': (6.0,4.0),
                 # 12pt labels get cutoff on 6x4 logplots, so use 10pt.
                 'font.size': 10,
                 # 10pt still needs a little more room on the xlabel:
                 'figure.subplot.bottom' : .125
             }
             rc = getattr(shell.config.Global, 'pylab_inline_rc', default_rc)
             pyplot.rcParams.update(rc)
             shell.config.Global.pylab_inline_rc = rc
             
             # Add 'figsize' to pyplot and to the user's namespace
             user_ns['figsize'] = pyplot.figsize = figsize
             shell.user_ns_hidden['figsize'] = figsize
         
         # 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(
             'matplotlib.figure','Figure',figure_to_svg
         )
         # Add display and display_png to the user's namespace
         user_ns['display'] = display
         shell.user_ns_hidden['display'] = display
         user_ns['display_svg'] = display_svg
         shell.user_ns_hidden['display_svg'] = display_svg
         user_ns['getfigs'] = getfigs
         shell.user_ns_hidden['getfigs'] = getfigs
 
     if import_all:
         s = ("from matplotlib.pylab import *\n"
              "from numpy import *\n")
         exec s in user_ns
         if shell is not None:
             exec s in shell.user_ns_hidden
 
 
 def pylab_activate(user_ns, gui=None, import_all=True):
     """Activate pylab mode in the user's namespace.
 
     Loads and initializes numpy, matplotlib and friends for interactive use.
 
     Parameters
     ----------
     user_ns : dict
       Namespace where the imports will occur.
 
     gui : optional, string
       A valid gui name following the conventions of the %gui magic.
 
     import_all : optional, boolean
       If true, an 'import *' is done from numpy and pylab.
 
     Returns
     -------
     The actual gui used (if not given as input, it was obtained from matplotlib
     itself, and will be needed next to configure IPython's gui integration.
     """
     gui, backend = find_gui_and_backend(gui)
     activate_matplotlib(backend)
     import_pylab(user_ns, backend)
 
     print """
 Welcome to pylab, a matplotlib-based Python environment [backend: %s].
 For more information, type 'help(pylab)'.""" % backend
     
     return gui
 

IPython/testing/iptest.py

@@ -1,427 +1,433
 # -*- coding: utf-8 -*-
 """IPython Test Suite Runner.
 
 This module provides a main entry point to a user script to test IPython
 itself from the command line. There are two ways of running this script:
 
 1. With the syntax `iptest all`.  This runs our entire test suite by
    calling this script (with different arguments) recursively.  This
    causes modules and package to be tested in different processes, using nose
    or trial where appropriate.
 2. With the regular nose syntax, like `iptest -vvs IPython`.  In this form
    the script simply calls nose, but with special command line flags and
    plugins loaded.
 
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2009  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 # Stdlib
 import os
 import os.path as path
 import signal
 import sys
 import subprocess
 import tempfile
 import time
 import warnings
 
 # Note: monkeypatch!
 # We need to monkeypatch a small problem in nose itself first, before importing
 # it for actual use.  This should get into nose upstream, but its release cycle
 # is slow and we need it for our parametric tests to work correctly.
 from IPython.testing import nosepatch
 # Now, proceed to import nose itself
 import nose.plugins.builtin
 from nose.core import TestProgram
 
 # Our own imports
 from IPython.utils.path import get_ipython_module_path
 from IPython.utils.process import find_cmd, pycmd2argv
 from IPython.utils.sysinfo import sys_info
 
 from IPython.testing import globalipapp
 from IPython.testing.plugin.ipdoctest import IPythonDoctest
 from IPython.external.decorators import KnownFailure
 
 pjoin = path.join
 
 
 #-----------------------------------------------------------------------------
 # Globals
 #-----------------------------------------------------------------------------
 
 
 #-----------------------------------------------------------------------------
 # Warnings control
 #-----------------------------------------------------------------------------
 
 # Twisted generates annoying warnings with Python 2.6, as will do other code
 # that imports 'sets' as of today
 warnings.filterwarnings('ignore', 'the sets module is deprecated',
                         DeprecationWarning )
 
 # This one also comes from Twisted
 warnings.filterwarnings('ignore', 'the sha module is deprecated',
                         DeprecationWarning)
 
 # Wx on Fedora11 spits these out
 warnings.filterwarnings('ignore', 'wxPython/wxWidgets release number mismatch',
                         UserWarning)
 
 #-----------------------------------------------------------------------------
 # Logic for skipping doctests
 #-----------------------------------------------------------------------------
 
 def test_for(mod, min_version=None):
     """Test to see if mod is importable."""
     try:
         __import__(mod)
     except (ImportError, RuntimeError):
         # GTK reports Runtime error if it can't be initialized even if  it's
         # importable.
         return False
     else:
         if min_version:
             return sys.modules[mod].__version__ >= min_version
         else:
             return True
 
 # Global dict where we can store information on what we have and what we don't
 # have available at test run time
 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
 #-----------------------------------------------------------------------------
 
 def report():
     """Return a string with a summary report of test-related variables."""
 
     out = [ sys_info(), '\n']
 
     avail = []
     not_avail = []
     
     for k, is_avail in have.items():
         if is_avail:
             avail.append(k)
         else:
             not_avail.append(k)
 
     if avail:
         out.append('\nTools and libraries available at test time:\n')
         avail.sort()
         out.append('   ' + ' '.join(avail)+'\n')
 
     if not_avail:
         out.append('\nTools and libraries NOT available at test time:\n')
         not_avail.sort()
         out.append('   ' + ' '.join(not_avail)+'\n')
         
     return ''.join(out)
 
 
 def make_exclude():
     """Make patterns of modules and packages to exclude from testing.
 
     For the IPythonDoctest plugin, we need to exclude certain patterns that
     cause testing problems.  We should strive to minimize the number of
     skipped modules, since this means untested code.
 
     These modules and packages will NOT get scanned by nose at all for tests.
     """
     # Simple utility to make IPython paths more readably, we need a lot of
     # these below
     ipjoin = lambda *paths: pjoin('IPython', *paths)
     
     exclusions = [ipjoin('external'),
                   pjoin('IPython_doctest_plugin'),
                   ipjoin('quarantine'),
                   ipjoin('deathrow'),
                   ipjoin('testing', 'attic'),
                   # This guy is probably attic material
                   ipjoin('testing', 'mkdoctests'),
                   # Testing inputhook will need a lot of thought, to figure out
                   # how to have tests that don't lock up with the gui event
                   # loops in the picture
                   ipjoin('lib', 'inputhook'),
                   # Config files aren't really importable stand-alone
                   ipjoin('config', 'default'),
                   ipjoin('config', 'profile'),
                   ]
 
     if not have['wx']:
         exclusions.append(ipjoin('lib', 'inputhookwx'))
         
     # We do this unconditionally, so that the test suite doesn't import
     # gtk, changing the default encoding and masking some unicode bugs.
     exclusions.append(ipjoin('lib', 'inputhookgtk'))
 
     # These have to be skipped on win32 because the use echo, rm, cd, etc.
     # See ticket https://bugs.launchpad.net/bugs/366982
     if sys.platform == 'win32':
         exclusions.append(ipjoin('testing', 'plugin', 'test_exampleip'))
         exclusions.append(ipjoin('testing', 'plugin', 'dtexample'))
 
     if not have['pexpect']:
         exclusions.extend([ipjoin('scripts', 'irunner'),
                            ipjoin('lib', 'irunner')])
 
     if not have['zmq']:
         exclusions.append(ipjoin('zmq'))
         exclusions.append(ipjoin('parallel'))
     
     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]
 
     return exclusions
 
 
 class IPTester(object):
     """Call that calls iptest or trial in a subprocess.
     """
     #: string, name of test runner that will be called
     runner = None
     #: list, parameters for test runner
     params = None
     #: list, arguments of system call to be made to call test runner
     call_args = None
     #: list, process ids of subprocesses we start (for cleanup)
     pids = None
     
     def __init__(self, runner='iptest', params=None):
         """Create new test runner."""
         p = os.path
         if runner == 'iptest':
             iptest_app = get_ipython_module_path('IPython.testing.iptest')
             self.runner = pycmd2argv(iptest_app) + sys.argv[1:]
         else:
             raise Exception('Not a valid test runner: %s' % repr(runner))
         if params is None:
             params = []
         if isinstance(params, str):
             params = [params]
         self.params = params
 
         # Assemble call
         self.call_args = self.runner+self.params
 
         # Store pids of anything we start to clean up on deletion, if possible
         # (on posix only, since win32 has no os.kill)
         self.pids = []
 
     if sys.platform == 'win32':
         def _run_cmd(self):
             # On Windows, use os.system instead of subprocess.call, because I
             # was having problems with subprocess and I just don't know enough
             # about win32 to debug this reliably.  Os.system may be the 'old
             # fashioned' way to do it, but it works just fine.  If someone
             # later can clean this up that's fine, as long as the tests run
             # reliably in win32.
             # What types of problems are you having. They may be related to
             # running Python in unboffered mode. BG.
             return os.system(' '.join(self.call_args))
     else:
         def _run_cmd(self):
             # print >> sys.stderr, '*** CMD:', ' '.join(self.call_args) # dbg
             subp = subprocess.Popen(self.call_args)
             self.pids.append(subp.pid)
             # If this fails, the pid will be left in self.pids and cleaned up
             # later, but if the wait call succeeds, then we can clear the
             # stored pid.
             retcode = subp.wait()
             self.pids.pop()
             return retcode
         
     def run(self):
         """Run the stored commands"""
         try:
             return self._run_cmd()
         except:
             import traceback
             traceback.print_exc()
             return 1  # signal failure
 
     def __del__(self):
         """Cleanup on exit by killing any leftover processes."""
 
         if not hasattr(os, 'kill'):
             return
         
         for pid in self.pids:
             try:
                 print 'Cleaning stale PID:', pid
                 os.kill(pid, signal.SIGKILL)
             except OSError:
                 # This is just a best effort, if we fail or the process was
                 # really gone, ignore it.
                 pass     
 
 
 def make_runners():
     """Define the top-level packages that need to be tested.
     """
 
     # Packages to be tested via nose, that only depend on the stdlib
     nose_pkg_names = ['config', 'core', 'extensions', 'frontend', 'lib',
                      'scripts', 'testing', 'utils' ]
     
     if have['zmq']:
         nose_pkg_names.append('parallel')
     
     # For debugging this code, only load quick stuff
     #nose_pkg_names = ['core', 'extensions']  # dbg
 
     # Make fully qualified package names prepending 'IPython.' to our name lists
     nose_packages = ['IPython.%s' % m for m in nose_pkg_names ]
 
     # Make runners
     runners = [ (v, IPTester('iptest', params=v)) for v in nose_packages ]
     
     return runners
 
 
 def run_iptest():
     """Run the IPython test suite using nose.
     
     This function is called when this script is **not** called with the form
     `iptest all`.  It simply calls nose with appropriate command line flags
     and accepts all of the standard nose arguments.
     """
 
     warnings.filterwarnings('ignore', 
         'This will be removed soon.  Use IPython.testing.util instead')
 
     argv = sys.argv + [ '--detailed-errors',  # extra info in tracebacks
                                                 
                         # Loading ipdoctest causes problems with Twisted, but
                         # our test suite runner now separates things and runs
                         # all Twisted tests with trial.
                         '--with-ipdoctest',
                         '--ipdoctest-tests','--ipdoctest-extension=txt',
                         
                         # We add --exe because of setuptools' imbecility (it
                         # blindly does chmod +x on ALL files).  Nose does the
                         # right thing and it tries to avoid executables,
                         # setuptools unfortunately forces our hand here.  This
                         # has been discussed on the distutils list and the
                         # setuptools devs refuse to fix this problem!
                         '--exe',
                         ]
 
     if nose.__version__ >= '0.11':
         # I don't fully understand why we need this one, but depending on what
         # directory the test suite is run from, if we don't give it, 0 tests
         # get run.  Specifically, if the test suite is run from the source dir
         # with an argument (like 'iptest.py IPython.core', 0 tests are run,
         # even if the same call done in this directory works fine).  It appears
         # that if the requested package is in the current dir, nose bails early
         # by default.  Since it's otherwise harmless, leave it in by default
         # for nose >= 0.11, though unfortunately nose 0.10 doesn't support it.
         argv.append('--traverse-namespace')
 
     # Construct list of plugins, omitting the existing doctest plugin, which
     # ours replaces (and extends).
     plugins = [IPythonDoctest(make_exclude()), KnownFailure()]
     for p in nose.plugins.builtin.plugins:
         plug = p()
         if plug.name == 'doctest':
             continue
         plugins.append(plug)
 
     # We need a global ipython running in this process
     globalipapp.start_ipython()
     # Now nose can run
     TestProgram(argv=argv, plugins=plugins)
 
 
 def run_iptestall():
     """Run the entire IPython test suite by calling nose and trial.
     
     This function constructs :class:`IPTester` instances for all IPython
     modules and package and then runs each of them.  This causes the modules
     and packages of IPython to be tested each in their own subprocess using
     nose or twisted.trial appropriately.
     """
 
     runners = make_runners()
 
     # Run the test runners in a temporary dir so we can nuke it when finished
     # to clean up any junk files left over by accident.  This also makes it
     # robust against being run in non-writeable directories by mistake, as the
     # temp dir will always be user-writeable.
     curdir = os.getcwd()
     testdir = tempfile.gettempdir()
     os.chdir(testdir)
 
     # Run all test runners, tracking execution time
     failed = []
     t_start = time.time()
     try:
         for (name, runner) in runners:
             print '*'*70
             print 'IPython test group:',name
             res = runner.run()
             if res:
                 failed.append( (name, runner) )
     finally:
         os.chdir(curdir)
     t_end = time.time()
     t_tests = t_end - t_start
     nrunners = len(runners)
     nfail = len(failed)
     # summarize results
     print
     print '*'*70
     print 'Test suite completed for system with the following information:'
     print report()
     print 'Ran %s test groups in %.3fs' % (nrunners, t_tests)
     print
     print 'Status:'
     if not failed:
         print 'OK'
     else:
         # If anything went wrong, point out what command to rerun manually to
         # see the actual errors and individual summary
         print 'ERROR - %s out of %s test groups failed.' % (nfail, nrunners)
         for name, failed_runner in failed:
             print '-'*40
             print 'Runner failed:',name
             print 'You may wish to rerun this one individually, with:'
             print ' '.join(failed_runner.call_args)
             print
 
 
 def main():
     for arg in sys.argv[1:]:
         if arg.startswith('IPython'):
             # This is in-process
             run_iptest()
     else:
         # This starts subprocesses
         run_iptestall()
 
 
 if __name__ == '__main__':
     main()

IPython/zmq/pylab/backend_inline.py

@@ -1,73 +1,83
 """Produce SVG versions of active plots for display by the rich Qt frontend.
 """
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 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
 
 # Local imports.
 from IPython.core.displaypub import publish_display_data
 from IPython.lib.pylabtools import figure_to_svg
 
 #-----------------------------------------------------------------------------
 # Functions
 #-----------------------------------------------------------------------------
 
 def show(close=False):
     """Show all figures as SVG payloads sent to the IPython clients.
 
     Parameters
     ----------
     close : bool, optional
       If true, a ``plt.close('all')`` call is automatically issued after
       sending all the SVG figures. If this is set, the figures will entirely
       removed from the internal list of figures.
     """
     for figure_manager in Gcf.get_all_fig_managers():
         send_svg_figure(figure_manager.canvas.figure)
     if close:
         matplotlib.pyplot.close('all')
 
 
 # This flag will be reset by draw_if_interactive when called
 show._draw_called = False
 
 
 def draw_if_interactive():
     """
     Is called after every pylab drawing command
     """
     # We simply flag we were called and otherwise do nothing.  At the end of
     # the code execution, a separate call to show_close() will act upon this.
     show._draw_called = True
 
 
 def flush_svg():
     """Call show, close all open figures, sending all SVG images.
 
     This is meant to be called automatically and will call show() if, during
     prior code execution, there had been any calls to draw_if_interactive.
     """
     if show._draw_called:
         # Show is called with the default close=False here, otherwise, the
         # Figure will be closed and not available for future plotting.
         show()
         show._draw_called = False
 
 
 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',
         {'image/svg+xml' : svg}
     )