ENH: add reusable matplotlib stylesheet

MANIFEST.in

@@ -23,6 +23,8 @@ recursive-include yt/visualization/volume_rendering/shaders *.fragmentshader *.v
 include yt/sample_data_registry.json
 include conftest.py
 include yt/py.typed
+include yt/default.mplstyle
+
 prune yt/frontends/_skeleton
 recursive-include yt/frontends/amrvac *.par
 exclude .codecov.yml .coveragerc .git-blame-ignore-revs .gitmodules .hgchurn .mailmap

conftest.py

@@ -145,7 +145,7 @@ def pytest_configure(config):
             r"Use Palette\.ADAPTIVE instead\.:DeprecationWarning",
         )
 
-    if NUMPY_VERSION < Version("1.19") and MPL_VERSION < Version("3.3"):
+    if NUMPY_VERSION < Version("1.19") and MPL_VERSION < Version("3.4"):
         # This warning is triggered from matplotlib in exactly one test at the time of writing
         # and exclusively on the minimal test env. Upgrading numpy or matplotlib resolves
         # the issue, so we can afford to ignore it.

doc/source/visualizing/plots.rst

@@ -2419,3 +2419,80 @@ an example that includes slices and phase plots:
     )
 
     mp.save_fig("multi_slice_phase")
+
+
+Using yt's style with matplotlib
+--------------------------------
+
+It is possible to use yt's plot style in outside of yt itself, with the
+:func:`~yt.funcs.matplotlib_style_context` context manager
+
+.. code-block:: python
+
+   import matplotlib.pyplot as plt
+   import numpy as np
+   import yt
+
+   plt.rcParams["font.size"] = 14
+
+   x = np.linspace(-np.pi, np.pi, 100)
+   y = np.sin(x)
+
+   with yt.funcs.matplotlib_style_context():
+       fig, ax = plt.subplots()
+       ax.plot(x, y)
+       ax.set(
+           xlabel=r"$x$",
+           ylabel=r"$y$",
+           title="A yt-styled matplotlib figure",
+       )
+
+Note that :func:`~yt.funcs.matplotlib_style_context` doesn't control the font
+size, so we adjust it manually in the preamble.
+
+With matplotlib 3.7 and newer, you can avoid importing yt altogether
+
+.. code-block:: python
+
+   # requires matplotlib>=3.7
+   import matplotlib.pyplot as plt
+   import numpy as np
+
+   plt.rcParams["font.size"] = 14
+
+   x = np.linspace(-np.pi, np.pi, 100)
+   y = np.sin(x)
+
+   with plt.style.context("yt.default"):
+       fig, ax = plt.subplots()
+       ax.plot(x, y)
+       ax.set(
+           xlabel=r"$x$",
+           ylabel=r"$y$",
+           title="A yt-styled matplotlib figure",
+       )
+
+and you can also enable yt's style without a context manager as
+
+.. code-block:: python
+
+   # requires matplotlib>=3.7
+   import matplotlib.pyplot as plt
+   import numpy as np
+
+   plt.style.use("yt.default")
+   plt.rcParams["font.size"] = 14
+
+   x = np.linspace(-np.pi, np.pi, 100)
+   y = np.sin(x)
+
+   fig, ax = plt.subplots()
+   ax.plot(x, y)
+   ax.set(
+       xlabel=r"$x$",
+       ylabel=r"$y$",
+       title="A yt-styled matplotlib figure",
+   )
+
+For more details, see `matplotlib's documentation
+<https://matplotlib.org/stable/tutorials/introductory/customizing.html#customizing-with-style-sheets>_`

yt/default.mplstyle

@@ -0,0 +1,14 @@
+# basic usage (requires matplotlib 3.7+)
+# >>> import matplotlib as mpl
+# >>> mpl.style.use("yt.default")
+
+xtick.top: True
+ytick.right: True
+xtick.minor.visible: True
+ytick.minor.visible: True
+xtick.direction: in
+ytick.direction: in
+
+font.family: stixgeneral
+
+mathtext.fontset: cm

yt/funcs.py

@@ -994,35 +994,22 @@ def get_brewer_cmap(cmap):
     return bmap.get_mpl_colormap(N=cmap[2])
 
 
-@contextlib.contextmanager
-def dummy_context_manager(*args, **kwargs):
-    yield
-
-
-def matplotlib_style_context(style_name=None, after_reset=False):
+def matplotlib_style_context(style="yt.default", after_reset=False):
     """Returns a context manager for controlling matplotlib style.
 
     Arguments are passed to matplotlib.style.context() if specified. Defaults
-    to setting "classic" style, after resetting to the default config parameters.
-
-    On older matplotlib versions (<=1.5.0) where matplotlib.style isn't
-    available, returns a dummy context manager.
+    to setting yt's "yt.default" style, after resetting to the default config parameters.
     """
-    if style_name is None:
-        import matplotlib
+    # FUTURE: this function should be deprecated in favour of matplotlib.style.context
+    # after support for matplotlib 3.6 and older versions is dropped.
+    import matplotlib.style
 
-        style_name = {"mathtext.fontset": "cm"}
-        if Version(matplotlib.__version__) >= Version("3.3.0"):
-            style_name["mathtext.fallback"] = "cm"
-        else:
-            style_name["mathtext.fallback_to_cm"] = True
-    try:
-        import matplotlib.style
+    from yt.visualization._commons import MPL_VERSION
 
-        return matplotlib.style.context(style_name, after_reset=after_reset)
-    except ImportError:
-        pass
-    return dummy_context_manager()
+    if style == "yt.default" and MPL_VERSION < Version("3.7"):
+        style = importlib_resources.files("yt") / "default.mplstyle"
+
+    return matplotlib.style.context(style, after_reset=after_reset)
 
 
 interactivity = False

yt/visualization/_commons.py

@@ -5,12 +5,18 @@
 from importlib.metadata import version
 from typing import TYPE_CHECKING, Optional, Type, TypeVar
 
+import matplotlib as mpl
 import numpy as np
 from more_itertools import always_iterable
 from packaging.version import Version
 
 from yt.config import ytcfg
 
+if sys.version_info >= (3, 9):
+    import importlib.resources as importlib_resources
+else:
+    import importlib_resources
+
 if sys.version_info >= (3, 10):
     pass
 else:
@@ -20,15 +26,16 @@
     from ._mpl_imports import FigureCanvasBase
 
 
-DEFAULT_FONT_PROPERTIES = {
-    "family": "stixgeneral",
-    "size": 18,
-}
-
 MPL_VERSION = Version(version("matplotlib"))
 
+_yt_style = mpl.rc_params_from_file(
+    importlib_resources.files("yt") / "default.mplstyle", use_default_template=False
+)
+DEFAULT_FONT_PROPERTIES = {"family": _yt_style["font.family"][0]}
+
 if MPL_VERSION >= Version("3.4"):
-    DEFAULT_FONT_PROPERTIES["math_fontfamily"] = "cm"
+    DEFAULT_FONT_PROPERTIES["math_fontfamily"] = _yt_style["mathtext.fontset"]
+del _yt_style
 
 
 def _get_supported_image_file_formats():

yt/visualization/plot_container.py

@@ -133,7 +133,7 @@ def __init__(self, data_source, figure_size=None, fontsize: Optional[float] = No
         if sys.version_info >= (3, 9):
             font_dict = DEFAULT_FONT_PROPERTIES | {"size": fontsize}
         else:
-            font_dict = {**DEFAULT_FONT_PROPERTIES, "size": fontsize}  # type:ignore
+            font_dict = {**DEFAULT_FONT_PROPERTIES, "size": fontsize}
 
         self._font_properties = FontProperties(**font_dict)
         self._font_color = None
@@ -451,10 +451,11 @@ def set_font(self, font_dict=None):
             self._font_color = font_dict.pop("color")
         # Set default values if the user does not explicitly set them.
         # this prevents reverting to the matplotlib defaults.
+        _default_size = {"size": self.__class__._default_font_size}
         if sys.version_info >= (3, 9):
-            font_dict = DEFAULT_FONT_PROPERTIES | font_dict
+            font_dict = DEFAULT_FONT_PROPERTIES | _default_size | font_dict
         else:
-            font_dict = {**DEFAULT_FONT_PROPERTIES, **font_dict}
+            font_dict = {**DEFAULT_FONT_PROPERTIES, **_default_size, **font_dict}
         self._font_properties = FontProperties(**font_dict)
         return self