feat: pylab.style support (is scoped per virtual kernel)

solara/server/patch.py

@@ -345,13 +345,66 @@ def wrapper():
 
 @once
 def patch_matplotlib():
+    import matplotlib
     import matplotlib._pylab_helpers
 
     prev = matplotlib._pylab_helpers.Gcf.figs
     matplotlib._pylab_helpers.Gcf.figs = context_dict_user("matplotlib.pylab.figure_managers", prev)  # type: ignore
 
+    RcParamsOriginal = matplotlib.RcParams
+    counter = 0
+    lock = threading.Lock()
+
+    class RcParamsScoped(context_dict, matplotlib.RcParams):
+        _was_initialized = False
+        _without_kernel_dict: Dict[Any, Any]
+
+        def __init__(self, *args, **kwargs) -> None:
+            self._init()
+            RcParamsOriginal.__init__(self, *args, **kwargs)
+
+        def _init(self):
+            nonlocal counter
+            with lock:
+                counter += 1
+            self._user_dict_name = f"matplotlib.rcParams:{counter}"
+            # this creates a copy of the CPython side of the dict
+            self._without_kernel_dict = dict(zip(dict.keys(self), dict.values(self)))
+            self._was_initialized = True
+
+        def _set(self, key, val):
+            # in matplotlib this directly calls dict.__setitem__
+            # which would not call context_dict.__setitem__
+            self[key] = val
+
+        def _get(self, key):
+            # same as _get
+            return self[key]
+
+        def _get_context_dict(self) -> dict:
+            if not self._was_initialized:
+                # since we monkey patch the class after __init__ was called
+                # we may have to do that later on
+                self._init()
+            if kernel_context.has_current_context():
+                context = kernel_context.get_current_context()
+                if self._user_dict_name not in context.user_dicts:
+                    # copy over the global settings when needed
+                    context.user_dicts[self._user_dict_name] = self._without_kernel_dict.copy()
+                return context.user_dicts[self._user_dict_name]
+            else:
+                return self._without_kernel_dict
+
+    matplotlib.RcParams = RcParamsScoped
+    matplotlib.rcParams.__class__ = RcParamsScoped
+    # we chose to monkeypatch the class, instead of re-assiging to reParams for 2 reasons:
+    # 1. the RcParams object could be imported in different namespaces
+    # 2. the rcParams has extra methods, which means we have to otherwise monkeypatch the context_dict
+
     def cleanup():
         matplotlib._pylab_helpers.Gcf.figs = prev
+        matplotlib.RcParams = RcParamsOriginal
+        matplotlib.rcParams.__class__ = RcParamsOriginal
 
     return cleanup
 
@@ -382,7 +435,7 @@ def patch():
     if "MPLBACKEND" not in os.environ:
         if ipykernel_version_major < 6:
             # changed in https://github.com/ipython/ipykernel/pull/591
-            os.environ["MPLBACKEND"] = "ipykernel.pylab.backend_inline"
+            os.environ["MPLBACKEND"] = "module://ipykernel.pylab.backend_inline"
         else:
             os.environ["MPLBACKEND"] = "module://matplotlib_inline.backend_inline"
 

tests/unit/matplotlib_test.py

@@ -31,20 +31,45 @@ def test_pylab(no_kernel_context):
 
         assert len(Gcf.get_all_fig_managers()) == 0
         plt.figure()
+
         assert len(Gcf.get_all_fig_managers()) == 1
+
+        default_color = (1, 1, 1, 0)
+        white = "white"
+        black = "black"
+        assert plt.rcParams["figure.facecolor"] in [default_color, white]
+        plt.style.use("default")
+        assert plt.rcParams["figure.facecolor"] == white
+
+        plt.style.use("dark_background")
+        assert plt.rcParams["figure.facecolor"] == black
+
         with context_1:
             assert len(Gcf.get_all_fig_managers()) == 0
             plt.figure()
+            assert plt.rcParams["figure.facecolor"] == black
             assert len(Gcf.get_all_fig_managers()) == 1
+            plt.style.use("default")
+            assert plt.rcParams["figure.facecolor"] == white
+
+        assert plt.rcParams["figure.facecolor"] == black
         assert len(Gcf.get_all_fig_managers()) == 1
+        plt.style.use("default")
+        assert plt.rcParams["figure.facecolor"] == white
+
         with context_2:
+            assert plt.rcParams["figure.facecolor"] == white
             assert len(Gcf.get_all_fig_managers()) == 0
             plt.figure()
             assert len(Gcf.get_all_fig_managers()) == 1
             plt.figure()
             assert len(Gcf.get_all_fig_managers()) == 2
+            plt.style.use("dark_background")
+            assert plt.rcParams["figure.facecolor"] == black
         with context_1:
             assert len(Gcf.get_all_fig_managers()) == 1
+            assert plt.rcParams["figure.facecolor"] == white
+        assert plt.rcParams["figure.facecolor"] == white
 
     finally:
         cleanup()