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# -*- coding: utf-8 -*-
# Copyright (c) Vispy Development Team. All Rights Reserved.
# Distributed under the (new) BSD License. See LICENSE.txt for more info.
Implements the global singleton app object.
from __future__ import division
import os
import sys
from . import backends, inputhook
from .. import config
from .base import BaseApplicationBackend as ApplicationBackend # noqa
from ..util import logger
from ..ext import six
class Application(object):
"""Representation of the vispy application
This wraps a native GUI application instance. Vispy has a default
instance of this class that can be created/obtained via
backend_name : str | None
The name of the backend application to use. If not specified,
Vispy tries to select a backend automatically. See ``vispy.use()``
for details.
Upon creating an Application object, a backend is selected, but the
native backend application object is only created when `create()`
is called or `native` is used. The Canvas and Timer do this
def __init__(self, backend_name=None):
self._backend_module = None
self._backend = None
def __repr__(self):
name = self.backend_name
if not name:
return '<Vispy app with no backend>'
return '<Vispy app, wrapping the %s GUI toolkit>' % name
def backend_name(self):
""" The name of the GUI backend that this app wraps.
if self._backend is not None:
return self._backend._vispy_get_backend_name()
return ''
def backend_module(self):
""" The module object that defines the backend.
return self._backend_module
def process_events(self):
""" Process all pending GUI events. If the mainloop is not
running, this should be done regularly to keep the visualization
interactive and to keep the event system going.
return self._backend._vispy_process_events()
def sleep(self, duration_sec):
""" Sleep for the given duration in seconds.
This is used to reduce
CPU stress when VisPy is run in interactive mode.
see for details
duration_sec: float
Time to sleep in seconds
def create(self):
""" Create the native application.
# Ensure that the native app exists
def is_interactive(self):
""" Determine if the user requested interactive mode.
# The Python interpreter sets sys.flags correctly, so use them!
if sys.flags.interactive:
return True
# IPython does not set sys.flags when -i is specified, so first
# check it if it is already imported.
if '__IPYTHON__' not in dir(six.moves.builtins):
return False
# Then we check the application singleton and determine based on
# a variable it sets.
# ipython >=3.0
from traitlets.config.application import Application as App
except ImportError:
# ipython <3.0
from IPython.config.application import Application as App
return App.initialized() and App.instance().interact
except (ImportError, AttributeError):
return False
def is_notebook(self):
"""Determine if the user is executing in a Jupyter Notebook"""
# 'get_ipython' is available in globals when running from
# IPython/Jupyter
ip = get_ipython()
return ip.has_trait('kernel')
except NameError:
return False
def run(self, allow_interactive=True):
""" Enter the native GUI event loop.
allow_interactive : bool
Is the application allowed to handle interactive mode for console
terminals? By default, typing ``python -i`` results in
an interactive shell that also regularly calls the VisPy event
loop. In this specific case, the run() function will terminate
immediately and rely on the interpreter's input loop to be run
after script execution.
if allow_interactive and self.is_interactive():
inputhook.set_interactive(enabled=True, app=self)
return self._backend._vispy_run()
def reuse(self):
""" Called when the application is reused in an interactive session.
This allow the backend to do stuff in the client when `use_app()` is
called multiple times by the user. For example, the notebook backends
need to inject JavaScript code as soon as `use_app()` is called.
return self._backend._vispy_reuse()
def quit(self):
""" Quit the native GUI event loop.
return self._backend._vispy_quit()
def native(self):
""" The native GUI application instance.
return self._backend._vispy_get_native_app()
def _use(self, backend_name=None):
"""Select a backend by name. See class docstring for details.
# See if we're in a specific testing mode, if so DONT check to see
# if it's a valid backend. If it isn't, it's a good thing we
# get an error later because we should have decorated our test
# with requires_application()
test_name = os.getenv('_VISPY_TESTING_APP', None)
# Check whether the given name is valid
if backend_name is not None:
if backend_name.lower() == 'default':
backend_name = None # Explicitly use default, avoid using test
elif backend_name.lower() not in BACKENDMAP:
raise ValueError('backend_name must be one of %s or None, not '
'%r' % (BACKEND_NAMES, backend_name))
elif test_name is not None:
backend_name = test_name.lower()
assert backend_name in BACKENDMAP
elif self.is_notebook():
backend_name = 'ipynb_webgl'
# Should we try and load any backend, or just this specific one?
try_others = backend_name is None
# Get backends to try ...
imported_toolkits = [] # Backends for which the native lib is imported
backends_to_try = []
if not try_others:
# We should never hit this, since we check above
assert backend_name.lower() in BACKENDMAP.keys()
# Add it
# See if a backend is loaded
for name, module_name, native_module_name in CORE_BACKENDS:
if native_module_name and native_module_name in sys.modules:
# See if a default is given
default_backend = config['default_backend'].lower()
if default_backend.lower() in BACKENDMAP.keys():
if default_backend not in backends_to_try:
# After this, try each one
for name, module_name, native_module_name in CORE_BACKENDS:
name = name.lower()
if name not in backends_to_try:
# Now try each one
for key in backends_to_try:
name, module_name, native_module_name = BACKENDMAP[key]
mod_name = 'backends.' + module_name
__import__(mod_name, globals(), level=1)
mod = getattr(backends, module_name)
if not mod.available:
msg = ('Could not import backend "%s":\n%s'
% (name, str(mod.why_not)))
if not try_others:
# Fail if user wanted to use a specific backend
raise RuntimeError(msg)
elif key in imported_toolkits:
# Warn if were unable to use an already imported toolkit
msg = ('Although %s is already imported, the %s backend '
'could not\nbe used ("%s"). \nNote that running '
'multiple GUI toolkits simultaneously can cause '
'side effects.' %
(native_module_name, name, str(mod.why_not)))
if backend_name is not None:
# Inform only if one isn't available
# Success!
self._backend_module = mod
logger.debug('Selected backend %s' % module_name)
raise RuntimeError('Could not import any of the backends. '
'You need to install any of %s. We recommend '
'PyQt' % [b[0] for b in CORE_BACKENDS])
# Store classes for app backend and canvas backend
self._backend = self.backend_module.ApplicationBackend()