matplotlib · OceanWolf · Jul 28, 2015 · Sep 30, 2016 · NelleV · Sep 30, 2016
diff --git a/.travis.yml b/.travis.yml
@@ -27,6 +27,9 @@ addons:
       - graphviz
       - libgeos-dev
       - otf-freefont
+      - libpangocairo-1.0-0
+      - libgirepository-1.0-1
+      - gir1.2-gtk-3.0
 #     - fonts-humor-sans
 #    sources:
 #      - debian-sid
@@ -112,7 +115,7 @@ install:
     pip install --upgrade setuptools
   - |
     # Install dependencies from pypi
-    pip install $PRE python-dateutil $NUMPY pyparsing!=2.1.6 $PANDAS pep8 cycler coveralls coverage
+    pip install $PRE python-dateutil $NUMPY pyparsing!=2.1.6 $PANDAS pep8 cycler coveralls coverage pgi cairocffi
     pip install $PRE -r doc-requirements.txt
 
     # Install nose from a build which has partial
@@ -160,7 +163,7 @@ script:
         if [[ $TRAVIS_OS_NAME == 'osx' ]]; then
           python tests.py $NOSE_ARGS $TEST_ARGS
         else
-          gdb -return-child-result -batch -ex r -ex bt --args python $PYTHON_ARGS tests.py $NOSE_ARGS $TEST_ARGS
+          xvfb-run gdb -return-child-result -batch -ex r -ex bt --args python $PYTHON_ARGS tests.py $NOSE_ARGS $TEST_ARGS
         fi
       else
         echo The following args are passed to pytest $PYTEST_ARGS

diff --git a/INSTALL b/INSTALL
@@ -235,6 +235,10 @@ backends and the capabilities they provide.
 :term:`pyqt` 4.4 or later
     The Qt4 widgets library python wrappers for the Qt4Agg backend
 
+:term:`PyGObject` or `pgi`
+    For Gtk3, MPL requires the installation of a GObject introspection library
+    for python, either `PyGObject` (also known as gi) or `pgi`.
+
 :term:`pygtk` 2.4 or later
     The python wrappers for the GTK widgets library for use with the
     GTK or GTKAgg backend

diff --git a/doc/glossary/index.rst b/doc/glossary/index.rst
@@ -64,6 +64,17 @@ Glossary
       channel.  PDF was designed in part as a next-generation document
       format to replace postscript
 
+  pgi
+      `pgi <https://pypi.python.org/pypi/pgi/>` exists as a relatively new
+      python wrapper to GTK3 and acts as a pure python alternative to PyGObject.
+      pgi still exists in its infancy, currently missing many features of
+      PyGObject.  However matplotlib does not use any of these missing features.
+
+  PyGObject
+      Like :term:`pygtk`, `PyGObject <http://www.pygtk.org/>` provides
+      python wrappers for the :term:`GTK` widgets library; unlike pygtk,
+      PyGObject wraps GTK3 instead of the now obsolete GTK2.
+
   pygtk
       `pygtk <http://www.pygtk.org/>`_ provides python wrappers for
       the :term:`GTK` widgets library for use with the GTK or GTKAgg

diff --git a/doc/users/whats_new/2015-07-30_pgi.rst b/doc/users/whats_new/2015-07-30_pgi.rst
@@ -0,0 +1,9 @@
+PGI - Pure Python GObject Introspection Bindings
+------------------------------------------------
+
+For the GTK3 backend, matplotlib now supports PGI bindings as an alternative
+to PyGObject.  By default matplotlib will still use PyGObject, otherwise it
+will look for pgi.  You can change this behaviour through the rcParam
+backend.gi_preference which takes either a string, or a list of strings in
+order of preference.
+
diff --git a/lib/matplotlib/__init__.py b/lib/matplotlib/__init__.py
@@ -1496,6 +1496,7 @@ def _jupyter_nbextension_paths():
     'matplotlib.tests.test_backend_ps',
     'matplotlib.tests.test_backend_qt4',
     'matplotlib.tests.test_backend_qt5',
+    'matplotlib.tests.test_backend_gtk3',
     'matplotlib.tests.test_backend_svg',
     'matplotlib.tests.test_basic',
     'matplotlib.tests.test_bbox_tight',

diff --git a/lib/matplotlib/backends/backend_cairo.py b/lib/matplotlib/backends/backend_cairo.py
@@ -29,25 +29,7 @@
 
 def _fn_name(): return sys._getframe(1).f_code.co_name
 
-try:
-    import cairocffi as cairo
-except ImportError:
-    try:
-        import cairo
-    except ImportError:
-        raise ImportError("Cairo backend requires that cairocffi or pycairo is installed.")
-    else:
-        HAS_CAIRO_CFFI = False
-else:
-    HAS_CAIRO_CFFI = True
-
-_version_required = (1,2,0)
-if cairo.version_info < _version_required:
-    raise ImportError ("Pycairo %d.%d.%d is installed\n"
-                       "Pycairo %d.%d.%d or later is required"
-                        % (cairo.version_info + _version_required))
-backend_version = cairo.version
-del _version_required
+from .cairo_compat import cairo, HAS_CAIRO_CFFI
 
 from matplotlib.backend_bases import RendererBase, GraphicsContextBase,\
      FigureManagerBase, FigureCanvasBase

diff --git a/lib/matplotlib/backends/backend_gtk3.py b/lib/matplotlib/backends/backend_gtk3.py
@@ -6,25 +6,7 @@
 import os, sys
 def fn_name(): return sys._getframe(1).f_code.co_name
 
-try:
-    import gi
-except ImportError:
-    raise ImportError("Gtk3 backend requires pygobject to be installed.")
-
-try:
-    gi.require_version("Gtk", "3.0")
-except AttributeError:
-    raise ImportError(
-        "pygobject version too old -- it must have require_version")
-except ValueError:
-    raise ImportError(
-        "Gtk3 backend requires the GObject introspection bindings for Gtk 3 "
-        "to be installed.")
-
-try:
-    from gi.repository import Gtk, Gdk, GObject, GLib
-except ImportError:
-    raise ImportError("Gtk3 backend requires pygobject to be installed.")
+from .gtk3_compat import Gtk, Gdk, GObject, GLib
 
 import matplotlib
 from matplotlib._pylab_helpers import Gcf
@@ -167,6 +149,12 @@ class FigureCanvasGTK3 (Gtk.DrawingArea, FigureCanvasBase):
                65421 : 'enter',
                }
 
+    modifier_keys = [
+                     (Gdk.ModifierType.MOD4_MASK, 'super'),
+                     (Gdk.ModifierType.MOD1_MASK, 'alt'),
+                     (Gdk.ModifierType.CONTROL_MASK, 'ctrl'),
+                    ]
+
     # Setting this as a static constant prevents
     # this resulting expression from leaking
     event_mask = (Gdk.EventMask.BUTTON_PRESS_MASK   |
@@ -293,12 +281,7 @@ def _get_key(self, event):
         else:
             key = None
 
-        modifiers = [
-                     (Gdk.ModifierType.MOD4_MASK, 'super'),
-                     (Gdk.ModifierType.MOD1_MASK, 'alt'),
-                     (Gdk.ModifierType.CONTROL_MASK, 'ctrl'),
-                    ]
-        for key_mask, prefix in modifiers:
+        for key_mask, prefix in self.modifier_keys:
             if event.state & key_mask:
                 key = '{0}+{1}'.format(prefix, key)
 

diff --git a/lib/matplotlib/backends/backend_gtk3agg.py b/lib/matplotlib/backends/backend_gtk3agg.py
@@ -9,7 +9,7 @@
 
 from . import backend_agg
 from . import backend_gtk3
-from .backend_cairo import cairo, HAS_CAIRO_CFFI
+from .cairo_compat import cairo, HAS_CAIRO_CFFI
 from matplotlib.figure import Figure
 from matplotlib import transforms
 
@@ -46,7 +46,7 @@ def on_draw_event(self, widget, ctx):
         else:
             bbox_queue = self._bbox_queue
 
-        if HAS_CAIRO_CFFI:
+        if HAS_CAIRO_CFFI and not isinstance(ctx, cairo.Context):
             ctx = cairo.Context._from_pointer(
                 cairo.ffi.cast('cairo_t **',
                                id(ctx) + object.__basicsize__)[0],

diff --git a/lib/matplotlib/backends/backend_gtk3cairo.py b/lib/matplotlib/backends/backend_gtk3cairo.py
@@ -5,12 +5,12 @@
 
 from . import backend_gtk3
 from . import backend_cairo
-from .backend_cairo import cairo, HAS_CAIRO_CFFI
+from .cairo_compat import cairo, HAS_CAIRO_CFFI
 from matplotlib.figure import Figure
 
 class RendererGTK3Cairo(backend_cairo.RendererCairo):
     def set_context(self, ctx):
-        if HAS_CAIRO_CFFI:
+        if HAS_CAIRO_CFFI and not isinstance(ctx, cairo.Context):
             ctx = cairo.Context._from_pointer(
                 cairo.ffi.cast(
                     'cairo_t **',

diff --git a/lib/matplotlib/backends/cairo_compat.py b/lib/matplotlib/backends/cairo_compat.py
@@ -0,0 +1,20 @@
+try:
+    import cairocffi as cairo
+except ImportError:
+    try:
+        import cairo
+    except ImportError:
+        raise ImportError(
+            "Cairo backend requires that cairocffi or pycairo is installed.")
+    else:
+        HAS_CAIRO_CFFI = False
+else:
+    HAS_CAIRO_CFFI = True
+
+_version_required = (1, 2, 0)
+if cairo.version_info < _version_required:
+    raise ImportError("Pycairo %d.%d.%d is installed\n"
+                      "Pycairo %d.%d.%d or later is required"
+                        % (cairo.version_info + _version_required))
+backend_version = cairo.version
+del _version_required
diff --git a/lib/matplotlib/backends/gtk3_compat.py b/lib/matplotlib/backends/gtk3_compat.py
@@ -0,0 +1,34 @@
+import matplotlib
+
+error_msg_gtk3 = "Gtk3 backend requires the installation of pygobject or pgi."
+
+# Import the first library that works from the rcParam list
+# throw ImportError if none works
+for lib in matplotlib.rcParams['backend.gi_preference']:
+    try:
+        gi = __import__(lib, globals(), locals(), [], 0)
+        break
+    except ImportError:
+        pass
+else:
+    raise ImportError(error_msg_gtk3)
+
+# Check version
+try:
+    gi.require_version("Gtk", "3.0")
+except AttributeError:
+    raise ImportError(
+        "pygobject version too old -- it must have require_version")
+except ValueError:
+    raise ImportError(
+        "Gtk3 backend requires the installation of GObject introspection "
+        "bindings for Gtk 3")
+
+# cleanly import pkgs to global scope
+try:
+    pkgs = ['Gtk', 'Gdk', 'GObject', 'GLib']
+    name = gi.__name__ + '.repository'
+    _temp = __import__(name, globals(), locals(), pkgs, 0)
+    globals().update(dict((k, getattr(_temp, k)) for k in pkgs))
+except (ImportError, AttributeError):
+    raise ImportError(error_msg_gtk3)
diff --git a/lib/matplotlib/rcsetup.py b/lib/matplotlib/rcsetup.py
@@ -410,6 +410,9 @@ def deprecate_axes_colorcycle(value):
 validate_stringlist = _listify_validator(six.text_type)
 validate_stringlist.__doc__ = 'return a list'
 
+validate_gi_preference = _listify_validator(ValidateInStrings(
+    'backend.gi_preference', ['gi', 'pgi']))
+
 validate_orientation = ValidateInStrings(
     'orientation', ['landscape', 'portrait'])
 
@@ -888,6 +891,7 @@ def validate_animation_writer_path(p):
     'backend_fallback':  [True, validate_bool],  # agg is certainly present
     'backend.qt4':       ['PyQt4', validate_qt4],
     'backend.qt5':       ['PyQt5', validate_qt5],
+    'backend.gi_preference':  [['gi', 'pgi'], validate_gi_preference],
     'webagg.port':       [8988, validate_int],
     'webagg.open_in_browser': [True, validate_bool],
     'webagg.port_retries': [50, validate_int],

diff --git a/lib/matplotlib/tests/test_backend_gtk3.py b/lib/matplotlib/tests/test_backend_gtk3.py
@@ -0,0 +1,60 @@
+from __future__ import (absolute_import, division, print_function,
+                        unicode_literals)
+
+from matplotlib.externals import six
+from matplotlib.externals.six import unichr
+from matplotlib import pyplot as plt
+from matplotlib.testing.decorators import cleanup, switch_backend
+from matplotlib.testing.decorators import knownfailureif
+from matplotlib._pylab_helpers import Gcf
+import copy
+
+try:
+    # mock in python 3.3+
+    from unittest import mock
+except ImportError:
+    import mock
+
+try:
+    from matplotlib.backends.gtk3_compat import Gtk, Gdk, GObject, GLib
+    HAS_GTK3 = True
+except ImportError:
+    HAS_GTK3 = False
+
+
+def simulate_key_press(canvas, key, modifiers=[]):
+    event = mock.Mock()
+
+    keyval = [k for k, v in six.iteritems(canvas.keyvald) if v == key]
+    if keyval:
+        keyval = keyval[0]
+    else:
+        keyval = ord(key)
+    event.keyval = keyval
+
+    event.state = 0
+    for key_mask, prefix in canvas.modifier_keys:
+        if prefix in modifiers:
+            event.state |= key_mask
+
+    canvas.key_press_event(None, event)
+
+
+@cleanup
+#@knownfailureif(not HAS_GTK3)
+@switch_backend('GTK3Agg')
+def test_fig_close():
+    #save the state of Gcf.figs
+    init_figs = copy.copy(Gcf.figs)
+
+    # make a figure using pyplot interface
+    fig = plt.figure()
+
+    # simulate user pressing the close shortcut
+    #simulate_key_press(fig.canvas, 'w', ['ctrl'])
+
+    plt.show()
+
+    # assert that we have removed the reference to the FigureManager
+    # that got added by plt.figure()
+    assert(init_figs == Gcf.figs)