Fix tick marker mirroring (matplotlib conversion)

plotly/matplotlylib/mpltools.py

@@ -266,15 +266,12 @@ def get_axes_bounds(fig):
     return (x_min, x_max), (y_min, y_max)
 
 
-def get_axis_mirror(main_spine, mirror_spine):
-    if main_spine and mirror_spine:
+def get_axis_mirror(main_spine, mirror_spine, main_tick_markers, mirror_tick_markers):
+    if main_spine and mirror_spine and main_tick_markers and mirror_tick_markers:
+        return True
+    if main_tick_markers and mirror_tick_markers:
         return "ticks"
-    elif main_spine and not mirror_spine:
-        return False
-    elif not main_spine and mirror_spine:
-        return False  # can't handle this case yet!
-    else:
-        return False  # nuttin'!
+    return False
 
 
 def get_bar_gap(bar_starts, bar_ends, tol=1e-10):

plotly/matplotlylib/renderer.py

@@ -168,8 +168,16 @@ def open_axes(self, ax, props):
         top_spine = mpltools.get_spine_visible(ax, "top")
         left_spine = mpltools.get_spine_visible(ax, "left")
         right_spine = mpltools.get_spine_visible(ax, "right")
-        xaxis["mirror"] = mpltools.get_axis_mirror(bottom_spine, top_spine)
-        yaxis["mirror"] = mpltools.get_axis_mirror(left_spine, right_spine)
+        bottom_tick_markers = ax.xaxis.get_tick_params()["bottom"]
+        top_tick_markers = ax.xaxis.get_tick_params()["top"]
+        left_tick_markers = ax.yaxis.get_tick_params()["left"]
+        right_tick_markers = ax.yaxis.get_tick_params()["right"]
+        xaxis["mirror"] = mpltools.get_axis_mirror(
+            bottom_spine, top_spine, bottom_tick_markers, top_tick_markers
+        )
+        yaxis["mirror"] = mpltools.get_axis_mirror(
+            left_spine, right_spine, left_tick_markers, right_tick_markers
+        )
         xaxis["showline"] = bottom_spine
         yaxis["showline"] = top_spine
 

plotly/matplotlylib/tests/__init__.py

@@ -0,0 +1,4 @@
+import matplotlib
+
+matplotlib.use("Agg")
+import matplotlib.pyplot as plt

plotly/matplotlylib/tests/test_renderer.py

@@ -0,0 +1,75 @@
+import plotly.tools as tls
+
+from . import plt
+
+def test_axis_mirror_with_spines_and_ticks():
+    """Test that mirror=True when both spines and ticks are visible on both sides."""
+    fig, ax = plt.subplots()
+    ax.plot([0, 1], [0, 1])
+
+    # Show all spines
+    ax.spines['top'].set_visible(True)
+    ax.spines['bottom'].set_visible(True)
+    ax.spines['left'].set_visible(True)
+    ax.spines['right'].set_visible(True)
+
+    # Show ticks on all sides
+    ax.tick_params(top=True, bottom=True, left=True, right=True)
+
+    plotly_fig = tls.mpl_to_plotly(fig)
+
+    assert plotly_fig.layout.xaxis.mirror == True
+    assert plotly_fig.layout.yaxis.mirror == True
+
+
+def test_axis_mirror_with_ticks_only():
+    """Test that mirror='ticks' when only ticks are visible on both sides."""
+    fig, ax = plt.subplots()
+    ax.plot([0, 1], [0, 1])
+
+    # Hide opposite spines
+    ax.spines['top'].set_visible(False)
+    ax.spines['right'].set_visible(False)
+
+    # Show ticks on all sides
+    ax.tick_params(top=True, bottom=True, left=True, right=True)
+
+    plotly_fig = tls.mpl_to_plotly(fig)
+
+    assert plotly_fig.layout.xaxis.mirror == "ticks"
+    assert plotly_fig.layout.yaxis.mirror == "ticks"
+
+
+def test_axis_mirror_false_with_one_sided_ticks():
+    """Test that mirror=False when ticks are only on one side."""
+    fig, ax = plt.subplots()
+    ax.plot([0, 1], [0, 1])
+
+    # Default matplotlib behavior - ticks only on bottom and left
+    ax.tick_params(top=False, bottom=True, left=True, right=False)
+
+    plotly_fig = tls.mpl_to_plotly(fig)
+
+    assert plotly_fig.layout.xaxis.mirror == False
+    assert plotly_fig.layout.yaxis.mirror == False
+
+
+def test_axis_mirror_mixed_configurations():
+    """Test different configurations for x and y axes."""
+    fig, ax = plt.subplots()
+    ax.plot([0, 1], [0, 1])
+
+    # X-axis: spines and ticks on both sides (mirror=True)
+    ax.spines['top'].set_visible(True)
+    ax.spines['bottom'].set_visible(True)
+    ax.tick_params(top=True, bottom=True)
+
+    # Y-axis: only ticks on both sides (mirror='ticks')
+    ax.spines['right'].set_visible(False)
+    ax.spines['left'].set_visible(True)
+    ax.tick_params(left=True, right=True)
+
+    plotly_fig = tls.mpl_to_plotly(fig)
+
+    assert plotly_fig.layout.xaxis.mirror == True
+    assert plotly_fig.layout.yaxis.mirror == "ticks"