matplotlib · raphaelquast · Mar 10, 2025 · Mar 10, 2025
diff --git a/lib/matplotlib/backends/backend_webagg_widget.py b/lib/matplotlib/backends/backend_webagg_widget.py
@@ -0,0 +1,113 @@
+"""Display a WebAgg HTML Widget in a Jupyter Notebook."""
+
+import io
+from base64 import b64encode
+
+import matplotlib as mpl
+from matplotlib.backend_bases import _Backend
+from matplotlib._pylab_helpers import Gcf
+from matplotlib.backends import backend_webagg_core as core
+from matplotlib.backends.backend_webagg import WebAggApplication
+
+try:
+    from IPython.display import display
+except ImportError as err:
+    raise RuntimeError("The WebAggWidget backend requires IPython.") from err
+
+try:
+    from ipywidgets import HTML, Layout
+except ImportError as err:
+    raise RuntimeError("The WebAggWidget backend requires ipywidgets.") from err
+
+
+class WebAggFigureWidget(HTML):
+    _margin_x, _margin_y = (20, 80)
+
+    def __init__(self, f=None):
+        super().__init__()
+
+        self.f = f
+        self._webagg_address = (
+            "http://{0}:{1}/{2}".format(
+                mpl.rcParams["webagg.address"],
+                WebAggApplication.port,
+                self.f.number
+                )
+            )
+        self._setup_widget()
+
+    def _setup_widget(self):
+        # TODO find a better way to get the required size to show the full figure
+        w = int(self.f.dpi * self.f.get_figwidth() + self._margin_x)
+        h = int((self.f.dpi * self.f.get_figheight() + self._margin_y))
+        layout = Layout(width=f"{w}px", height=f"{h}px")
+
+        self.value = (
+            f"<iframe src={self._webagg_address} "
+            "style='width: 100%; height: 100%; border:none;' scrolling='no' "
+            "frameborder='0' allowtransparency='true'></iframe>"
+            )
+        self.layout = layout
+
+        # Add a callback to dynamically adjust the widget layout on resize of the figure
+        def cb(event):
+            self.layout.width = f"{(event.width + self._margin_x):.0f}px"
+            self.layout.height = f"{(event.height + self._margin_y):.0f}px"
+        self.f.canvas.mpl_connect("resize_event", cb)
+
+    def _repr_mimebundle_(self, **kwargs):
+        # attach a png of the figure for static display
+        buf = io.BytesIO()
+        self.f.savefig(buf, format='png', dpi='figure')
+        data_url = b64encode(buf.getvalue()).decode('utf-8')
+
+        data = {
+            'text/plain': str(self.f),
+            'image/png': data_url,
+            'application/vnd.jupyter.widget-view+json': {
+                'version_major': 2,
+                'version_minor': 0,
+                'model_id': self._model_id
+            }
+        }
+        return data
+
+
+class FigureManagerWebAggWidget(core.FigureManagerWebAgg):
+    _toolbar2_class = core.NavigationToolbar2WebAgg
+
+    @classmethod
+    def pyplot_show(cls, *, block=None):
+        managers = Gcf.get_all_fig_managers()
+        for m in managers:
+            # Only display figures that have not yet been shown
+            if m.canvas._webagg_widget is None:
+                display(m.canvas._get_widget())
+
+
+class FigureCanvasWebAggWidget(core.FigureCanvasWebAggCore):
+    manager_class = FigureManagerWebAggWidget
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+
+        self._webagg_widget = None
+
+    def _get_widget(self):
+        # Return cached widget if it already exists
+        if self._webagg_widget is None:
+            WebAggApplication.initialize()
+            WebAggApplication.start()
+
+            self._webagg_widget = WebAggFigureWidget(f=self.figure)
+
+        return self._webagg_widget
+
+    def show(self):
+        return self._get_widget()
+
+
+@_Backend.export
+class _BackendWebAggWidget(_Backend):
+    FigureCanvas = FigureCanvasWebAggWidget
+    FigureManager = FigureManagerWebAggWidget