From f12ed744306d111b2ff82bcb5edda2de6cf0479a Mon Sep 17 00:00:00 2001
From: Roberto Moura <roberto@ffmoura.com>
Date: Mon, 10 Aug 2026 20:45:28 +0000
Subject: [PATCH 1/3] Convert matplotlib step drawstyles to plotly line shapes

---
 plotly/matplotlylib/mpltools.py            | 17 +++++++++++++++++
 plotly/matplotlylib/renderer.py            |  3 +++
 plotly/matplotlylib/tests/test_renderer.py | 16 ++++++++++++++++
 3 files changed, 36 insertions(+)

diff --git a/plotly/matplotlylib/mpltools.py b/plotly/matplotlylib/mpltools.py
index e1198c9792..fbfc77e01e 100644
--- a/plotly/matplotlylib/mpltools.py
+++ b/plotly/matplotlylib/mpltools.py
@@ -278,6 +278,23 @@ def get_bar_gap(bar_starts, bar_ends, tol=1e-10):
             return min(max(gap0 / bar_delta, 0.0), 1.0)
 
 
+DRAWSTYLE_SHAPE_MAP = {
+    "steps": "vh",
+    "steps-pre": "vh",
+    "steps-post": "hv",
+    "steps-mid": "hvh",
+}
+
+
+def convert_drawstyle(drawstyle):
+    """Convert a matplotlib line drawstyle to a plotly line shape.
+
+    Matplotlib draws steps as vertical/horizontal segments; plotly's
+    ``line.shape`` expresses the same via "vh", "hv" and "hvh".
+    """
+    return DRAWSTYLE_SHAPE_MAP.get(drawstyle)
+
+
 def convert_rgba_array(color_list):
     clean_color_list = list()
     for c in color_list:
diff --git a/plotly/matplotlylib/renderer.py b/plotly/matplotlylib/renderer.py
index 65bbcfabb1..4c0d7e8b81 100644
--- a/plotly/matplotlylib/renderer.py
+++ b/plotly/matplotlylib/renderer.py
@@ -407,6 +407,9 @@ def draw_marked_line(self, **props):
                     color=color,
                     width=props["linestyle"]["linewidth"],
                     dash=mpltools.convert_dash(props["linestyle"]["dasharray"]),
+                    shape=mpltools.convert_drawstyle(
+                        props["linestyle"]["drawstyle"]
+                    ),
                 )
             else:
                 shape = dict(
diff --git a/plotly/matplotlylib/tests/test_renderer.py b/plotly/matplotlylib/tests/test_renderer.py
index 02dd6cf34a..7cf8cbaf5a 100644
--- a/plotly/matplotlylib/tests/test_renderer.py
+++ b/plotly/matplotlylib/tests/test_renderer.py
@@ -37,6 +37,22 @@ def test_no_fake_legend_shapes_with_native_legend():
     assert len(plotly_fig.layout.annotations) == 0
 
 
+def test_drawstyle_maps_to_line_shape():
+    cases = {
+        "steps-pre": "vh",
+        "steps": "vh",
+        "steps-post": "hv",
+        "steps-mid": "hvh",
+    }
+    for drawstyle, shape in cases.items():
+        fig, ax = plt.subplots()
+        ax.plot([0, 1, 2], [0, 1, 0], drawstyle=drawstyle)
+
+        plotly_fig = tls.mpl_to_plotly(fig)
+
+        assert plotly_fig.data[0].line.shape == shape
+
+
 def test_legend_disabled_when_no_matplotlib_legend():
     """Test that legend is not enabled when no matplotlib legend is present."""
     fig, ax = plt.subplots()

From 0304e152db4ec7b259e885f87447c3d4049650bb Mon Sep 17 00:00:00 2001
From: Roberto Moura <roberto@ffmoura.com>
Date: Sun, 4 Oct 2026 02:26:00 +0100
Subject: [PATCH 2/3] Run ruff format

---
 plotly/matplotlylib/renderer.py | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/plotly/matplotlylib/renderer.py b/plotly/matplotlylib/renderer.py
index 4c0d7e8b81..eacb98fc0b 100644
--- a/plotly/matplotlylib/renderer.py
+++ b/plotly/matplotlylib/renderer.py
@@ -407,9 +407,7 @@ def draw_marked_line(self, **props):
                     color=color,
                     width=props["linestyle"]["linewidth"],
                     dash=mpltools.convert_dash(props["linestyle"]["dasharray"]),
-                    shape=mpltools.convert_drawstyle(
-                        props["linestyle"]["drawstyle"]
-                    ),
+                    shape=mpltools.convert_drawstyle(props["linestyle"]["drawstyle"]),
                 )
             else:
                 shape = dict(

From f902129f18846a6891e0f61a875c9b2cc0cf3715 Mon Sep 17 00:00:00 2001
From: Roberto Moura <roberto@ffmoura.com>
Date: Sun, 4 Oct 2026 01:28:09 +0000
Subject: [PATCH 3/3] Add changelog entry

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

diff --git a/CHANGELOG.md b/CHANGELOG.md
index ea837e3d0b..92ef8247ee 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 ### Fixed
 - Fix concurrent first access to lazily initialized graph object properties, which could raise `ValueError("Invalid value")` [[#5691](https://github.com/plotly/plotly.py/pull/5691)], with thanks to @hb1915 for the contribution!
 - Fix `mpl_to_plotly` crashing on touching bars (such as `plt.hist`) due to floating-point noise producing negative `bargap` values by clamping `bargap` to `[0, 1]` [[#5696](https://github.com/plotly/plotly.py/pull/5696)], with thanks to @robertoffmoura for the contribution!
+- Fix `mpl_to_plotly` drawing step plots with diagonal lines instead of vertical/horizontal step segments by mapping matplotlib step drawstyles (`steps-pre`, `steps-post`, `steps-mid`) to plotly line shapes [[#5697](https://github.com/plotly/plotly.py/pull/5697)], with thanks to @robertoffmoura for the contribution!
 - Fix `px.sunburst`, `px.treemap` and `px.icicle` listing sectors in a different order on every run when `path` is used with a Polars DataFrame; sectors now follow their order of first appearance for all dataframe backends [[#5766](https://github.com/plotly/plotly.py/pull/5766)], with thanks to @Irahan2 for the contribution!
 
 ## [7.1.0] - 2026-09-15