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Rework backend loading.
This is preliminary work towards fixing the runtime detection of default backend problem (the first step being to make it easier to check whether a backend *can* be loaded). No publically visible API is changed. Backend loading now defines default versions of `backend_version`, `draw_if_interactive`, and `show` using the same inheritance strategy as builtin backends do. For non-interactive backends (which don't override `mainloop`), restore the default implementation of `show()` that prints a warning when run from a console (the backend refactor accidentally removed this error message as it provided a silent default `show()`). The `_Backend` class had to be moved to the end of the module as `FigureManagerBase` needs to be defined first. The `ShowBase` class had to be moved even after that as it depends on the `_Backend` class.
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‎lib/matplotlib/backend_bases.py

+127-114
Original file line numberDiff line numberDiff line change
@@ -41,6 +41,7 @@
4141
from contextlib import contextmanager
4242
from functools import partial
4343
import importlib
44+
import inspect
4445
import io
4546
import os
4647
import sys
@@ -126,120 +127,6 @@ def get_registered_canvas_class(format):
126127
return backend_class
127128

128129

129-
class _Backend(object):
130-
# A backend can be defined by using the following pattern:
131-
#
132-
# @_Backend.export
133-
# class FooBackend(_Backend):
134-
# # override the attributes and methods documented below.
135-
136-
# The following attributes and methods must be overridden by subclasses.
137-
138-
# The `FigureCanvas` and `FigureManager` classes must be defined.
139-
FigureCanvas = None
140-
FigureManager = None
141-
142-
# The following methods must be left as None for non-interactive backends.
143-
# For interactive backends, `trigger_manager_draw` should be a function
144-
# taking a manager as argument and triggering a canvas draw, and `mainloop`
145-
# should be a function taking no argument and starting the backend main
146-
# loop.
147-
trigger_manager_draw = None
148-
mainloop = None
149-
150-
# The following methods will be automatically defined and exported, but
151-
# can be overridden.
152-
153-
@classmethod
154-
def new_figure_manager(cls, num, *args, **kwargs):
155-
"""Create a new figure manager instance.
156-
"""
157-
# This import needs to happen here due to circular imports.
158-
from matplotlib.figure import Figure
159-
fig_cls = kwargs.pop('FigureClass', Figure)
160-
fig = fig_cls(*args, **kwargs)
161-
return cls.new_figure_manager_given_figure(num, fig)
162-
163-
@classmethod
164-
def new_figure_manager_given_figure(cls, num, figure):
165-
"""Create a new figure manager instance for the given figure.
166-
"""
167-
canvas = cls.FigureCanvas(figure)
168-
manager = cls.FigureManager(canvas, num)
169-
return manager
170-
171-
@classmethod
172-
def draw_if_interactive(cls):
173-
if cls.trigger_manager_draw is not None and is_interactive():
174-
manager = Gcf.get_active()
175-
if manager:
176-
cls.trigger_manager_draw(manager)
177-
178-
@classmethod
179-
def show(cls, block=None):
180-
"""Show all figures.
181-
182-
`show` blocks by calling `mainloop` if *block* is ``True``, or if it
183-
is ``None`` and we are neither in IPython's ``%pylab`` mode, nor in
184-
`interactive` mode.
185-
"""
186-
if cls.mainloop is None:
187-
return
188-
managers = Gcf.get_all_fig_managers()
189-
if not managers:
190-
return
191-
for manager in managers:
192-
manager.show()
193-
if block is None:
194-
# Hack: Are we in IPython's pylab mode?
195-
from matplotlib import pyplot
196-
try:
197-
# IPython versions >= 0.10 tack the _needmain attribute onto
198-
# pyplot.show, and always set it to False, when in %pylab mode.
199-
ipython_pylab = not pyplot.show._needmain
200-
except AttributeError:
201-
ipython_pylab = False
202-
block = not ipython_pylab and not is_interactive()
203-
# TODO: The above is a hack to get the WebAgg backend working with
204-
# ipython's `%pylab` mode until proper integration is implemented.
205-
if get_backend() == "WebAgg":
206-
block = True
207-
if block:
208-
cls.mainloop()
209-
210-
# This method is the one actually exporting the required methods.
211-
212-
@staticmethod
213-
def export(cls):
214-
for name in ["FigureCanvas",
215-
"FigureManager",
216-
"new_figure_manager",
217-
"new_figure_manager_given_figure",
218-
"draw_if_interactive",
219-
"show"]:
220-
setattr(sys.modules[cls.__module__], name, getattr(cls, name))
221-
222-
# For back-compatibility, generate a shim `Show` class.
223-
224-
class Show(ShowBase):
225-
def mainloop(self):
226-
return cls.mainloop()
227-
228-
setattr(sys.modules[cls.__module__], "Show", Show)
229-
return cls
230-
231-
232-
class ShowBase(_Backend):
233-
"""
234-
Simple base class to generate a show() callable in backends.
235-
236-
Subclass must override mainloop() method.
237-
"""
238-
239-
def __call__(self, block=None):
240-
return self.show(block=block)
241-
242-
243130
class RendererBase(object):
244131
"""An abstract base class to handle drawing/rendering operations.
245132
@@ -3366,3 +3253,129 @@ def set_message(self, s):
33663253
Message text
33673254
"""
33683255
pass
3256+
3257+
3258+
class _Backend(object):
3259+
# A backend can be defined by using the following pattern:
3260+
#
3261+
# @_Backend.export
3262+
# class FooBackend(_Backend):
3263+
# # override the attributes and methods documented below.
3264+
3265+
# May be overridden by the subclass.
3266+
backend_version = "unknown"
3267+
# The `FigureCanvas` class must be overridden.
3268+
FigureCanvas = None
3269+
# For interactive backends, the `FigureManager` class must be overridden.
3270+
FigureManager = FigureManagerBase
3271+
# The following methods must be left as None for non-interactive backends.
3272+
# For interactive backends, `trigger_manager_draw` should be a function
3273+
# taking a manager as argument and triggering a canvas draw, and `mainloop`
3274+
# should be a function taking no argument and starting the backend main
3275+
# loop.
3276+
trigger_manager_draw = None
3277+
mainloop = None
3278+
3279+
# The following methods will be automatically defined and exported, but
3280+
# can be overridden.
3281+
3282+
@classmethod
3283+
def new_figure_manager(cls, num, *args, **kwargs):
3284+
"""Create a new figure manager instance.
3285+
"""
3286+
# This import needs to happen here due to circular imports.
3287+
from matplotlib.figure import Figure
3288+
fig_cls = kwargs.pop('FigureClass', Figure)
3289+
fig = fig_cls(*args, **kwargs)
3290+
return cls.new_figure_manager_given_figure(num, fig)
3291+
3292+
@classmethod
3293+
def new_figure_manager_given_figure(cls, num, figure):
3294+
"""Create a new figure manager instance for the given figure.
3295+
"""
3296+
canvas = cls.FigureCanvas(figure)
3297+
manager = cls.FigureManager(canvas, num)
3298+
return manager
3299+
3300+
@classmethod
3301+
def draw_if_interactive(cls):
3302+
if cls.trigger_manager_draw is not None and is_interactive():
3303+
manager = Gcf.get_active()
3304+
if manager:
3305+
cls.trigger_manager_draw(manager)
3306+
3307+
@classmethod
3308+
def show(cls, block=None):
3309+
"""Show all figures.
3310+
3311+
`show` blocks by calling `mainloop` if *block* is ``True``, or if it
3312+
is ``None`` and we are neither in IPython's ``%pylab`` mode, nor in
3313+
`interactive` mode.
3314+
"""
3315+
if cls.mainloop is None:
3316+
frame = inspect.currentframe()
3317+
while frame:
3318+
if frame.f_code.co_filename in [
3319+
"<stdin>", "<ipython console>"]:
3320+
warnings.warn("""\
3321+
Your currently selected backend does not support show().
3322+
Please select a GUI backend in your matplotlibrc file ('{}')
3323+
or with matplotlib.use()""".format(matplotlib.matplotlib_fname()))
3324+
break
3325+
else:
3326+
frame = frame.f_back
3327+
return
3328+
managers = Gcf.get_all_fig_managers()
3329+
if not managers:
3330+
return
3331+
for manager in managers:
3332+
manager.show()
3333+
if block is None:
3334+
# Hack: Are we in IPython's pylab mode?
3335+
from matplotlib import pyplot
3336+
try:
3337+
# IPython versions >= 0.10 tack the _needmain attribute onto
3338+
# pyplot.show, and always set it to False, when in %pylab mode.
3339+
ipython_pylab = not pyplot.show._needmain
3340+
except AttributeError:
3341+
ipython_pylab = False
3342+
block = not ipython_pylab and not is_interactive()
3343+
# TODO: The above is a hack to get the WebAgg backend working with
3344+
# ipython's `%pylab` mode until proper integration is implemented.
3345+
if get_backend() == "WebAgg":
3346+
block = True
3347+
if block:
3348+
cls.mainloop()
3349+
3350+
# This method is the one actually exporting the required methods.
3351+
3352+
@staticmethod
3353+
def export(cls):
3354+
for name in ["backend_version",
3355+
"FigureCanvas",
3356+
"FigureManager",
3357+
"new_figure_manager",
3358+
"new_figure_manager_given_figure",
3359+
"draw_if_interactive",
3360+
"show"]:
3361+
setattr(sys.modules[cls.__module__], name, getattr(cls, name))
3362+
3363+
# For back-compatibility, generate a shim `Show` class.
3364+
3365+
class Show(ShowBase):
3366+
def mainloop(self):
3367+
return cls.mainloop()
3368+
3369+
setattr(sys.modules[cls.__module__], "Show", Show)
3370+
return cls
3371+
3372+
3373+
class ShowBase(_Backend):
3374+
"""
3375+
Simple base class to generate a show() callable in backends.
3376+
3377+
Subclass must override mainloop() method.
3378+
"""
3379+
3380+
def __call__(self, block=None):
3381+
return self.show(block=block)

‎lib/matplotlib/backends/__init__.py

+27-45
Original file line numberDiff line numberDiff line change
@@ -3,11 +3,13 @@
33

44
import six
55

6-
import matplotlib
7-
import inspect
8-
import traceback
9-
import warnings
6+
import importlib
107
import logging
8+
import traceback
9+
10+
import matplotlib
11+
from matplotlib.backend_bases import _Backend
12+
1113

1214
_log = logging.getLogger(__name__)
1315

@@ -47,50 +49,30 @@ def pylab_setup(name=None):
4749
'''
4850
# Import the requested backend into a generic module object
4951
if name is None:
50-
# validates, to match all_backends
5152
name = matplotlib.get_backend()
52-
if name.startswith('module://'):
53-
backend_name = name[9:]
54-
else:
55-
backend_name = 'backend_' + name
56-
backend_name = backend_name.lower() # until we banish mixed case
57-
backend_name = 'matplotlib.backends.%s' % backend_name.lower()
58-
59-
# the last argument is specifies whether to use absolute or relative
60-
# imports. 0 means only perform absolute imports.
61-
backend_mod = __import__(backend_name, globals(), locals(),
62-
[backend_name], 0)
63-
64-
# Things we pull in from all backends
65-
new_figure_manager = backend_mod.new_figure_manager
66-
67-
# image backends like pdf, agg or svg do not need to do anything
68-
# for "show" or "draw_if_interactive", so if they are not defined
69-
# by the backend, just do nothing
70-
def do_nothing_show(*args, **kwargs):
71-
frame = inspect.currentframe()
72-
fname = frame.f_back.f_code.co_filename
73-
if fname in ('<stdin>', '<ipython console>'):
74-
warnings.warn("""
75-
Your currently selected backend, '%s' does not support show().
76-
Please select a GUI backend in your matplotlibrc file ('%s')
77-
or with matplotlib.use()""" %
78-
(name, matplotlib.matplotlib_fname()))
79-
80-
def do_nothing(*args, **kwargs):
81-
pass
82-
83-
backend_version = getattr(backend_mod, 'backend_version', 'unknown')
84-
85-
show = getattr(backend_mod, 'show', do_nothing_show)
86-
87-
draw_if_interactive = getattr(backend_mod, 'draw_if_interactive',
88-
do_nothing)
89-
90-
_log.info('backend %s version %s' % (name, backend_version))
53+
backend_name = (name[9:] if name.startswith("module://")
54+
else "matplotlib.backends.backend_{}".format(name.lower()))
55+
56+
backend_mod = importlib.import_module(backend_name)
57+
Backend = type(str("Backend"), (_Backend,), vars(backend_mod))
58+
_log.info('backend %s version %s', name, Backend.backend_version)
9159

9260
# need to keep a global reference to the backend for compatibility
9361
# reasons. See https://github.com/matplotlib/matplotlib/issues/6092
9462
global backend
9563
backend = name
96-
return backend_mod, new_figure_manager, draw_if_interactive, show
64+
65+
# We want to get functions out of a class namespace and call them *without
66+
# the first argument being an instance of the class*. This works directly
67+
# on Py3. On Py2, we need to remove the check that the first argument be
68+
# an instance of the class. The only relevant case is if `.im_self` is
69+
# None, in which case we need to use `.im_func` (if we have a bound method
70+
# (e.g. a classmethod), everything is fine).
71+
def _dont_check_first_arg(func):
72+
return (func.im_func if getattr(func, "im_self", 0) is None
73+
else func)
74+
75+
return (backend_mod,
76+
_dont_check_first_arg(Backend.new_figure_manager),
77+
_dont_check_first_arg(Backend.draw_if_interactive),
78+
_dont_check_first_arg(Backend.show))

‎lib/matplotlib/backends/backend_pdf.py

+1-3
Original file line numberDiff line numberDiff line change
@@ -2594,11 +2594,9 @@ def print_pdf(self, filename, **kwargs):
25942594
file.close()
25952595

25962596

2597-
class FigureManagerPdf(FigureManagerBase):
2598-
pass
2597+
FigureManagerPdf = FigureManagerBase
25992598

26002599

26012600
@_Backend.export
26022601
class _BackendPdf(_Backend):
26032602
FigureCanvas = FigureCanvasPdf
2604-
FigureManager = FigureManagerPdf

‎lib/matplotlib/backends/backend_ps.py

+1-3
Original file line numberDiff line numberDiff line change
@@ -1723,8 +1723,7 @@ def pstoeps(tmpfile, bbox=None, rotated=False):
17231723
shutil.move(epsfile, tmpfile)
17241724

17251725

1726-
class FigureManagerPS(FigureManagerBase):
1727-
pass
1726+
FigureManagerPS = FigureManagerBase
17281727

17291728

17301729
# The following Python dictionary psDefs contains the entries for the
@@ -1770,4 +1769,3 @@ class FigureManagerPS(FigureManagerBase):
17701769
@_Backend.export
17711770
class _BackendPS(_Backend):
17721771
FigureCanvas = FigureCanvasPS
1773-
FigureManager = FigureManagerPS

‎lib/matplotlib/backends/backend_svg.py

+2-3
Original file line numberDiff line numberDiff line change
@@ -1252,8 +1252,8 @@ def _print_svg(self, filename, svgwriter, **kwargs):
12521252
def get_default_filetype(self):
12531253
return 'svg'
12541254

1255-
class FigureManagerSVG(FigureManagerBase):
1256-
pass
1255+
1256+
FigureManagerSVG = FigureManagerBase
12571257

12581258

12591259
svgProlog = """\
@@ -1267,4 +1267,3 @@ class FigureManagerSVG(FigureManagerBase):
12671267
@_Backend.export
12681268
class _BackendSVG(_Backend):
12691269
FigureCanvas = FigureCanvasSVG
1270-
FigureManager = FigureManagerSVG

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