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Warn when trying to start a GUI event loop out of the main thread. #15504

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Merged
merged 3 commits into from
Feb 11, 2020
Merged

Warn when trying to start a GUI event loop out of the main thread. #15504

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268d498
Rework exporting of backend functions in pyplot.
anntzer Oct 24, 2019
5062e9f
Warn when trying to start a GUI event loop out of the main thread.
anntzer Oct 24, 2019
ad90166
Some explanatory comments.
anntzer Dec 13, 2019
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68 changes: 50 additions & 18 deletions lib/matplotlib/pyplot.py
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,10 @@
import re
import sys
import time
try:
import threading
except ImportError:
import dummy_threading as threading

from cycler import cycler
import matplotlib
Expand Down Expand Up @@ -175,6 +179,11 @@ def findobj(o=None, match=None, include_self=True):
return o.findobj(match, include_self=include_self)


def _get_required_interactive_framework(backend_mod):
return getattr(
backend_mod.FigureCanvas, "required_interactive_framework", None)


def switch_backend(newbackend):
"""
Close all open figures and set the Matplotlib backend.
Expand All @@ -188,6 +197,8 @@ def switch_backend(newbackend):
newbackend : str
The name of the backend to use.
"""
global _backend_mod

close("all")

if newbackend is rcsetup._auto_backend_sentinel:
Expand All @@ -210,15 +221,17 @@ def switch_backend(newbackend):
rcParamsOrig["backend"] = "agg"
return

# Backends are implemented as modules, but "inherit" default method
# implementations from backend_bases._Backend. This is achieved by
# creating a "class" that inherits from backend_bases._Backend and whose
# body is filled with the module's globals.

backend_name = cbook._backend_module_name(newbackend)
backend_mod = importlib.import_module(backend_name)
Backend = type(
"Backend", (matplotlib.backend_bases._Backend,), vars(backend_mod))
_log.debug("Loaded backend %s version %s.",
newbackend, Backend.backend_version)

required_framework = getattr(
Backend.FigureCanvas, "required_interactive_framework", None)
class backend_mod(matplotlib.backend_bases._Backend):
locals().update(vars(importlib.import_module(backend_name)))

required_framework = _get_required_interactive_framework(backend_mod)
if required_framework is not None:
current_framework = cbook._get_running_interactive_framework()
if (current_framework and required_framework
Expand All @@ -228,23 +241,42 @@ def switch_backend(newbackend):
"framework, as {!r} is currently running".format(
newbackend, required_framework, current_framework))

# Update both rcParams and rcDefaults so restoring the defaults later with
# rcdefaults won't change the backend. A bit of overkill as 'backend' is
# already in style.core.STYLE_BLACKLIST, but better to be safe.
rcParams['backend'] = rcParamsDefault['backend'] = newbackend
_log.debug("Loaded backend %s version %s.",
newbackend, backend_mod.backend_version)

global _backend_mod, new_figure_manager, draw_if_interactive, _show
rcParams['backend'] = rcParamsDefault['backend'] = newbackend
_backend_mod = backend_mod
new_figure_manager = Backend.new_figure_manager
draw_if_interactive = Backend.draw_if_interactive
_show = Backend.show
for func_name in ["new_figure_manager", "draw_if_interactive", "show"]:
globals()[func_name].__signature__ = inspect.signature(
getattr(backend_mod, func_name))

# Need to keep a global reference to the backend for compatibility reasons.
# See https://github.com/matplotlib/matplotlib/issues/6092
matplotlib.backends.backend = newbackend


def show(*args, **kw):
def _warn_if_gui_out_of_main_thread():
if (_get_required_interactive_framework(_backend_mod)
and threading.current_thread() is not threading.main_thread()):
cbook._warn_external(
"Starting a Matplotlib GUI outside of the main thread will likely "
"fail.")


# This function's signature is rewritten upon backend-load by switch_backend.
def new_figure_manager(*args, **kwargs):
"""Create a new figure manager instance."""
_warn_if_gui_out_of_main_thread()
return _backend_mod.new_figure_manager(*args, **kwargs)


# This function's signature is rewritten upon backend-load by switch_backend.
def draw_if_interactive(*args, **kwargs):
return _backend_mod.draw_if_interactive(*args, **kwargs)


# This function's signature is rewritten upon backend-load by switch_backend.
def show(*args, **kwargs):
"""
Display all figures.

Expand All @@ -263,8 +295,8 @@ def show(*args, **kw):
This is experimental, and may be set to ``True`` or ``False`` to
override the blocking behavior described above.
"""
global _show
return _show(*args, **kw)
_warn_if_gui_out_of_main_thread()
return _backend_mod.show(*args, **kwargs)


def isinteractive():
Expand Down