From 269ae8c0fe74780c015a7a3ca876b21d269aa059 Mon Sep 17 00:00:00 2001
From: Roberto Moura <roberto@ffmoura.com>
Date: Tue, 11 Aug 2026 09:38:16 +0000
Subject: [PATCH] Convert matplotlib stairs plots to plotly step lines

---
 plotly/matplotlylib/renderer.py            | 36 ++++++++++++++++++++++
 plotly/matplotlylib/tests/test_renderer.py | 11 +++++++
 2 files changed, 47 insertions(+)

diff --git a/plotly/matplotlylib/renderer.py b/plotly/matplotlylib/renderer.py
index a282c67cec..53705f47ae 100644
--- a/plotly/matplotlylib/renderer.py
+++ b/plotly/matplotlylib/renderer.py
@@ -9,6 +9,7 @@
 
 import warnings
 
+import matplotlib.patches as mpatches
 import plotly.graph_objs as go
 from plotly.matplotlylib.mplexporter import Renderer
 from plotly.matplotlylib import mpltools
@@ -599,6 +600,9 @@ def draw_path(self, **props):
         is_bar = mpltools.is_bar(self.current_mpl_ax.containers, **props)
         if is_bar:
             self.current_bars += [props]
+        elif isinstance(props["mplobj"], mpatches.StepPatch):
+            self.msg += "    Drawing a step path\n"
+            self._draw_step_path(props)
         else:
             self.msg += "    This path isn't a bar, not drawing\n"
             warnings.warn(
@@ -606,6 +610,38 @@ def draw_path(self, **props):
                 "of a bar chart. Ignoring."
             )
 
+    def _draw_step_path(self, props):
+        """Draw a matplotlib StepPatch as a step line trace."""
+        if props["coordinates"] != "data":
+            self.msg += "    Step path is not in data coordinates, not drawing\n"
+            return
+        style = props["style"]
+        x = []
+        y = []
+        for x0, y0 in props["data"]:
+            if not x or x0 != x[-1] or y0 != y[-1]:
+                x.append(x0)
+                y.append(y0)
+        if len(x) < 2:
+            self.msg += "    Step path has fewer than 2 points, not drawing\n"
+            return
+        self.plotly_fig.add_trace(
+            go.Scatter(
+                x=x,
+                y=y,
+                mode="lines",
+                line=go.scatter.Line(
+                    color=mpltools.merge_color_and_opacity(
+                        style["edgecolor"], style["alpha"]
+                    ),
+                    width=style["edgewidth"],
+                    dash=mpltools.convert_dash(style["dasharray"]),
+                ),
+                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 f56d830917..136117a0b4 100644
--- a/plotly/matplotlylib/tests/test_renderer.py
+++ b/plotly/matplotlylib/tests/test_renderer.py
@@ -199,3 +199,14 @@ def test_filled_path_collection_date_xaxis():
     filled = [t for t in plotly_fig.data if t.fill == "toself"]
     assert len(filled) >= 1
     assert all(isinstance(x, str) for x in filled[0].x)
+
+
+def test_stairs_converts_to_step_line():
+    fig, ax = plt.subplots()
+    ax.stairs([0.0, 1.0, 0.0], [0.0, 1.0, 2.0, 3.0])
+    plotly_fig = tls.mpl_to_plotly(fig)
+    assert len(plotly_fig.data) == 1
+    trace = plotly_fig.data[0]
+    assert trace.mode == "lines"
+    assert tuple(trace.x) == (0.0, 1.0, 1.0, 2.0, 2.0, 3.0)
+    assert tuple(trace.y) == (0.0, 0.0, 1.0, 1.0, 0.0, 0.0)