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Merge pull request #28162 from meeseeksmachine/auto-backport-of-pr-27948-on-v3.9.x
Backport PR #27948 on branch v3.9.x (Move IPython backend mapping to Matplotlib and support entry points)
2 parents da9d058 + 2fec35a commit 971f5e9

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‎.github/workflows/tests.yml

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@@ -59,7 +59,8 @@ jobs:
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delete-font-cache: true
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- os: ubuntu-20.04
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python-version: 3.9
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extra-requirements: '-r requirements/testing/extra.txt'
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# One CI run tests ipython/matplotlib-inline before backend mapping moved to mpl
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extra-requirements: '-r requirements/testing/extra.txt "ipython<8.24" "matplotlib-inline<0.1.7"'
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CFLAGS: "-fno-lto" # Ensure that disabling LTO works.
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# https://github.com/matplotlib/matplotlib/pull/26052#issuecomment-1574595954
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# https://www.riverbankcomputing.com/pipermail/pyqt/2023-November/045606.html

‎doc/users/next_whats_new/backend_registry.rst

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New :class:`~matplotlib.backends.registry.BackendRegistry` class is the single
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source of truth for available backends. The singleton instance is
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``matplotlib.backends.backend_registry``.
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``matplotlib.backends.backend_registry``. It is used internally by Matplotlib,
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and also IPython (and therefore Jupyter) starting with IPython 8.24.0.
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There are three sources of backends: built-in (source code is within the
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Matplotlib repository), explicit ``module://some.backend`` syntax (backend is
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obtained by loading the module), or via an entry point (self-registering
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backend in an external package).
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To obtain a list of all registered backends use:
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>>> from matplotlib.backends import backend_registry
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>>> backend_registry.list_all()

‎galleries/users_explain/figure/backends.rst

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@@ -175,7 +175,8 @@ QtAgg Agg rendering in a Qt_ canvas (requires PyQt_ or `Qt for Python`_,
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more details.
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ipympl Agg rendering embedded in a Jupyter widget (requires ipympl_).
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This backend can be enabled in a Jupyter notebook with
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``%matplotlib ipympl``.
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``%matplotlib ipympl`` or ``%matplotlib widget``. Works with
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Jupyter ``lab`` and ``notebook>=7``.
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GTK3Agg Agg rendering to a GTK_ 3.x canvas (requires PyGObject_ and
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pycairo_). This backend can be activated in IPython with
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``%matplotlib gtk3``.
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backend can be activated in IPython with ``%matplotlib tk``.
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nbAgg Embed an interactive figure in a Jupyter classic notebook. This
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backend can be enabled in Jupyter notebooks via
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``%matplotlib notebook``.
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``%matplotlib notebook`` or ``%matplotlib nbagg``. Works with
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Jupyter ``notebook<7`` and ``nbclassic``.
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WebAgg On ``show()`` will start a tornado server with an interactive
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figure.
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GTK3Cairo Cairo rendering to a GTK_ 3.x canvas (requires PyGObject_ and
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========= ================================================================
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.. note::
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The names of builtin backends case-insensitive; e.g., 'QtAgg' and
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The names of builtin backends are case-insensitive; e.g., 'QtAgg' and
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'qtagg' are equivalent.
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.. _`Anti-Grain Geometry`: http://agg.sourceforge.net/antigrain.com/
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.. _wxWidgets: https://www.wxwidgets.org/
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.. _ipympl: https://www.matplotlib.org/ipympl
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.. _ipympl_install:
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ipympl
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^^^^^^
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The Jupyter widget ecosystem is moving too fast to support directly in
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Matplotlib. To install ipympl:
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The ipympl backend is in a separate package that must be explicitly installed
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if you wish to use it, for example:
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.. code-block:: bash
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‎galleries/users_explain/figure/figure_intro.rst

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@@ -52,14 +52,20 @@ Notebooks and IDEs
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If you are using a Notebook (e.g. `Jupyter <https://jupyter.org>`_) or an IDE
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that renders Notebooks (PyCharm, VSCode, etc), then they have a backend that
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will render the Matplotlib Figure when a code cell is executed. One thing to
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be aware of is that the default Jupyter backend (``%matplotlib inline``) will
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will render the Matplotlib Figure when a code cell is executed. The default
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Jupyter backend (``%matplotlib inline``) creates static plots that
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by default trim or expand the figure size to have a tight box around Artists
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added to the Figure (see :ref:`saving_figures`, below). If you use a backend
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other than the default "inline" backend, you will likely need to use an ipython
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"magic" like ``%matplotlib notebook`` for the Matplotlib :ref:`notebook
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<jupyter_notebooks_jupyterlab>` or ``%matplotlib widget`` for the `ipympl
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<https://matplotlib.org/ipympl/>`_ backend.
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added to the Figure (see :ref:`saving_figures`, below). For interactive plots
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in Jupyter you will need to use an ipython "magic" like ``%matplotlib widget``
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for the `ipympl <https://matplotlib.org/ipympl/>`_ backend in ``jupyter lab``
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or ``notebook>=7``, or ``%matplotlib notebook`` for the Matplotlib
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:ref:`notebook <jupyter_notebooks_jupyterlab>` in ``notebook<7`` or
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``nbclassic``.
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.. note::
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The `ipympl <https://matplotlib.org/ipympl/>`_ backend is in a separate
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package, see :ref:`Installing ipympl <ipympl_install>`.
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.. figure:: /_static/FigureNotebook.png
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:alt: Image of figure generated in Jupyter Notebook with notebook
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.. seealso::
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:ref:`interactive_figures`.
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.. note::
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If you only need to use the classic notebook (i.e. ``notebook<7``),
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you can use:
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.. sourcecode:: ipython
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%matplotlib notebook
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.. _standalone-scripts-and-interactive-use:
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Standalone scripts and interactive use
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QtAgg backend.
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When run from a script, or interactively (e.g. from an
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`iPython shell <https://ipython.readthedocs.io/en/stable/>`_) the Figure
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`IPython shell <https://ipython.readthedocs.io/en/stable/>`_) the Figure
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will not be shown until we call ``plt.show()``. The Figure will appear in
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a new GUI window, and usually will have a toolbar with Zoom, Pan, and other tools
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for interacting with the Figure. By default, ``plt.show()`` blocks

‎galleries/users_explain/figure/writing_a_backend_pyplot_interface.rst

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2. **Showing figures**: `.pyplot.show()` calls a module-level ``show()``
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function, which is typically generated via the ``ShowBase`` class and its
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``mainloop`` method.
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Registering a backend
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---------------------
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For a new backend to be usable via ``matplotlib.use()`` or IPython
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``%matplotlib`` magic command, it must be compatible with one of the three ways
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supported by the :class:`~matplotlib.backends.registry.BackendRegistry`:
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Built-in
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^^^^^^^^
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A backend built into Matplotlib must have its name and
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``FigureCanvas.required_interactive_framework`` hard-coded in the
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:class:`~matplotlib.backends.registry.BackendRegistry`. If the backend module
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is not ``f"matplotlib.backends.backend_{backend_name.lower()}"`` then there
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must also be an entry in the ``BackendRegistry._name_to_module``.
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module:// syntax
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^^^^^^^^^^^^^^^^
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Any backend in a separate module (not built into Matplotlib) can be used by
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specifying the path to the module in the form ``module://some.backend.module``.
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An example is ``module://mplcairo.qt`` for
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`mplcairo <https:////github.com/matplotlib/mplcairo>`_. The backend's
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interactive framework will be taken from its
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``FigureCanvas.required_interactive_framework``.
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Entry point
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^^^^^^^^^^^
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An external backend module can self-register as a backend using an
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``entry point`` in its ``pyproject.toml`` such as the one used by
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``matplotlib-inline``:
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.. code-block:: toml
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[project.entry-points."matplotlib.backend"]
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inline = "matplotlib_inline.backend_inline"
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The backend's interactive framework will be taken from its
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``FigureCanvas.required_interactive_framework``. All entry points are loaded
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together but only when first needed, such as when a backend name is not
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recognised as a built-in backend, or when
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:meth:`~matplotlib.backends.registry.BackendRegistry.list_all` is first called.

‎lib/matplotlib/__init__.py

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backend names, which are case-insensitive:
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- interactive backends:
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GTK3Agg, GTK3Cairo, GTK4Agg, GTK4Cairo, MacOSX, nbAgg, QtAgg,
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GTK3Agg, GTK3Cairo, GTK4Agg, GTK4Cairo, MacOSX, nbAgg, notebook, QtAgg,
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QtCairo, TkAgg, TkCairo, WebAgg, WX, WXAgg, WXCairo, Qt5Agg, Qt5Cairo
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- non-interactive backends:
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agg, cairo, pdf, pgf, ps, svg, template
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or a string of the form: ``module://my.module.name``.
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notebook is a synonym for nbAgg.
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Switching to an interactive backend is not possible if an unrelated
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event loop has already been started (e.g., switching to GTK3Agg if a
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TkAgg window has already been opened). Switching to a non-interactive

‎lib/matplotlib/backend_bases.py

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# `ipython --auto`). This cannot be done at import time due to
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# ordering issues, so we do it when creating a canvas, and should only
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# be done once per class (hence the `cache`).
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if sys.modules.get("IPython") is None:
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# This function will not be needed when Python 3.12, the latest version
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# supported by IPython < 8.24, reaches end-of-life in late 2028.
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# At that time this function can be made a no-op and deprecated.
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mod_ipython = sys.modules.get("IPython")
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if mod_ipython is None or mod_ipython.version_info[:2] >= (8, 24):
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# Use of backend2gui is not needed for IPython >= 8.24 as the
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# functionality has been moved to Matplotlib.
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return
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import IPython
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ip = IPython.get_ipython()
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if not ip:
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canvas = None
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if backend is not None:
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# Return a specific canvas class, if requested.
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canvas_class = (
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importlib.import_module(cbook._backend_module_name(backend))
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.FigureCanvas)
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from .backends.registry import backend_registry
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canvas_class = backend_registry.load_backend_module(backend).FigureCanvas
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if not hasattr(canvas_class, f"print_{fmt}"):
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raise ValueError(
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f"The {backend!r} backend does not support {fmt} output")

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