From 9c873572ed4f5a1b2a0219eb688f737252fc43f4 Mon Sep 17 00:00:00 2001
From: Roberto Moura <roberto@ffmoura.com>
Date: Wed, 2 Sep 2026 15:48:28 +0000
Subject: [PATCH 1/4] Convert fill polygons to filled scatter traces

---
 plotly/matplotlylib/renderer.py            | 25 ++++++++++++++++++++++
 plotly/matplotlylib/tests/test_renderer.py | 18 ++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/plotly/matplotlylib/renderer.py b/plotly/matplotlylib/renderer.py
index be10cd9af9..7c6fb93ffb 100644
--- a/plotly/matplotlylib/renderer.py
+++ b/plotly/matplotlylib/renderer.py
@@ -786,6 +786,12 @@ def draw_path(self, **props):
         elif isinstance(props["mplobj"], mpatches.StepPatch):
             self.msg += "    Drawing a step path\n"
             self._draw_step_path(props)
+        elif (
+            isinstance(props["mplobj"], mpatches.Polygon)
+            and props["coordinates"] == "data"
+        ):
+            self.msg += "    Drawing a filled polygon\n"
+            self._draw_filled_polygon(props)
         else:
             self.msg += "    This path isn't a bar, not drawing\n"
             warnings.warn(
@@ -848,6 +854,25 @@ def _draw_step_path(self, props):
             )
         )
 
+    def _draw_filled_polygon(self, props):
+        """Draw a matplotlib Polygon patch as a filled scatter trace."""
+        style = props["style"]
+        verts = props["data"]
+        facecolor = _export_color(style["facecolor"])
+        edgecolor = _export_color(style["edgecolor"])
+        self.plotly_fig.add_trace(
+            go.Scatter(
+                x=self._convert_x_dates([v[0] for v in verts]),
+                y=[v[1] for v in verts],
+                mode="lines",
+                line=go.scatter.Line(color=edgecolor, width=style["edgewidth"]),
+                fill="toself",
+                fillcolor=facecolor,
+                xaxis="x{0}".format(self.axis_ct),
+                yaxis="y{0}".format(self.axis_ct),
+            )
+        )
+
     def draw_text(self, **props):
         """Create an annotation dict for a text obj.
 
diff --git a/plotly/matplotlylib/tests/test_renderer.py b/plotly/matplotlylib/tests/test_renderer.py
index a355db7dc4..9116d21dd4 100644
--- a/plotly/matplotlylib/tests/test_renderer.py
+++ b/plotly/matplotlylib/tests/test_renderer.py
@@ -852,6 +852,24 @@ def test_uneven_custom_date_xtickvals_are_converted():
     )
 
 
+def test_fill_converts():
+    """plt.fill polygons convert to filled scatter traces."""
+    x = np.linspace(0, 2 * np.pi, 50)
+    fig, ax = plt.subplots()
+    ax.fill(x, np.sin(x), "g")
+
+    plotly_fig = tls.mpl_to_plotly(fig)
+
+    assert len(plotly_fig.data) == 1
+    trace = plotly_fig.data[0]
+    assert trace.type == "scatter"
+    assert trace.fill == "toself"
+    assert np.allclose(trace.x, x)
+    assert np.allclose(trace.y, np.sin(x))
+    assert trace.fillcolor == "#007F00"
+    assert trace.line.color == "rgba(0,0,0,0)"
+
+
 def test_custom_date_xtickvals_given_as_numbers_are_converted():
     """Custom date ticks given as matplotlib date numbers must be converted
     to date strings."""

From 5d432a39e1a038f363cc074f1e223b62ca3f146e Mon Sep 17 00:00:00 2001
From: Roberto Moura <roberto@ffmoura.com>
Date: Tue, 6 Oct 2026 08:41:32 +0000
Subject: [PATCH 2/4] Support legend labels on filled polygon traces

---
 plotly/matplotlylib/renderer.py            |  9 ++++++++
 plotly/matplotlylib/tests/test_renderer.py | 24 ++++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/plotly/matplotlylib/renderer.py b/plotly/matplotlylib/renderer.py
index 7c6fb93ffb..738bf5ef45 100644
--- a/plotly/matplotlylib/renderer.py
+++ b/plotly/matplotlylib/renderer.py
@@ -860,8 +860,17 @@ def _draw_filled_polygon(self, props):
         verts = props["data"]
         facecolor = _export_color(style["facecolor"])
         edgecolor = _export_color(style["edgecolor"])
+        mplobj = props.get("mplobj")
+        label = mplobj.get_label() if mplobj is not None else None
+        if not label or (isinstance(label, str) and label.startswith("_")):
+            label = None
+            showlegend = False
+        else:
+            showlegend = None
         self.plotly_fig.add_trace(
             go.Scatter(
+                name=label,
+                showlegend=showlegend,
                 x=self._convert_x_dates([v[0] for v in verts]),
                 y=[v[1] for v in verts],
                 mode="lines",
diff --git a/plotly/matplotlylib/tests/test_renderer.py b/plotly/matplotlylib/tests/test_renderer.py
index 9116d21dd4..25aa435091 100644
--- a/plotly/matplotlylib/tests/test_renderer.py
+++ b/plotly/matplotlylib/tests/test_renderer.py
@@ -870,6 +870,30 @@ def test_fill_converts():
     assert trace.line.color == "rgba(0,0,0,0)"
 
 
+def test_fill_with_legend_label():
+    """plt.fill polygons with labels export their name and show in legend."""
+    fig, ax = plt.subplots()
+    ax.fill([0, 1, 2], [0, 2, 0], "b", label="Shaded Area")
+    ax.fill([0, 1, 2], [0, 1, 0], "g")
+    ax.plot([0, 1, 2], [1, 1, 1], "r-", label="Threshold")
+    ax.legend()
+
+    plotly_fig = tls.mpl_to_plotly(fig)
+
+    assert plotly_fig.layout.showlegend == True
+    assert len(plotly_fig.data) == 3
+
+    labeled_fill = next(
+        t for t in plotly_fig.data if t.fill == "toself" and t.name == "Shaded Area"
+    )
+    assert labeled_fill.showlegend is not False
+
+    unlabeled_fill = next(
+        t for t in plotly_fig.data if t.fill == "toself" and t.name is None
+    )
+    assert unlabeled_fill.showlegend is False
+
+
 def test_custom_date_xtickvals_given_as_numbers_are_converted():
     """Custom date ticks given as matplotlib date numbers must be converted
     to date strings."""

From 57bca9b7d6f835dde8957f6291e7e5f08f9cdb3d Mon Sep 17 00:00:00 2001
From: Roberto Moura <roberto@ffmoura.com>
Date: Tue, 6 Oct 2026 08:46:11 +0000
Subject: [PATCH 3/4] Add changelog entry

---
 CHANGELOG.md | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index b45532a79b..9a26bb619a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,9 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 ## Unreleased
 
+### Added
+- Add support for converting matplotlib fill polygons (`plt.fill`) to filled scatter traces in `mpl_to_plotly`, with thanks to @robertoffmoura for the contribution!
+
 ### Fixed
 - Fix `mpl_to_plotly` tick marker mirroring, axis positioning, and trace visibility for twinned and overlaid subplots (such as `twinx` and `twiny`) [[#5310](https://github.com/plotly/plotly.py/pull/5310)], with thanks to @robertoffmoura for the contribution!
 - Fix `mpl_to_plotly` losing matplotlib axis line colors by exporting the color of each axis's displayed spine to the plotly x and y axis `linecolor` [[#5311](https://github.com/plotly/plotly.py/pull/5311)], with thanks to @robertoffmoura for the contribution!

From 63ee8ff2921628fbdf4362cadfb3a66c27db292f Mon Sep 17 00:00:00 2001
From: Roberto Moura <roberto@ffmoura.com>
Date: Tue, 6 Oct 2026 09:03:23 +0000
Subject: [PATCH 4/4] Update changelog entry with PR number 5795

---
 CHANGELOG.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9a26bb619a..963109e29e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,7 +5,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 ## Unreleased
 
 ### Added
-- Add support for converting matplotlib fill polygons (`plt.fill`) to filled scatter traces in `mpl_to_plotly`, with thanks to @robertoffmoura for the contribution!
+- Add support for converting matplotlib fill polygons (`plt.fill`) to filled scatter traces in `mpl_to_plotly` [[#5795](https://github.com/plotly/plotly.py/pull/5795)], with thanks to @robertoffmoura for the contribution!
 
 ### Fixed
 - Fix `mpl_to_plotly` tick marker mirroring, axis positioning, and trace visibility for twinned and overlaid subplots (such as `twinx` and `twiny`) [[#5310](https://github.com/plotly/plotly.py/pull/5310)], with thanks to @robertoffmoura for the contribution!