Allow sharing locators across axises.

anntzer · anntzer · commit ec0ea847490a · 2025-04-18T10:36:29.000+02:00
Locally changing the assigned axis seems to be the most practical
solution, if not the most elegant.
diff --git a/lib/matplotlib/axis.py b/lib/matplotlib/axis.py
@@ -1527,14 +1527,14 @@ def get_ticklines(self, minor=False):
 
     def get_majorticklocs(self):
         """Return this Axis' major tick locations in data coordinates."""
-        return self.major.locator()
+        return self.major.locator._call_with_axis(self)
 
     def get_minorticklocs(self):
         """Return this Axis' minor tick locations in data coordinates."""
         # Remove minor ticks duplicating major ticks.
-        minor_locs = np.asarray(self.minor.locator())
+        minor_locs = np.asarray(self.minor.locator._call_with_axis(self))
         if self.remove_overlapping_locs:
-            major_locs = self.major.locator()
+            major_locs = self.major.locator._call_with_axis(self)
             transform = self._scale.get_transform()
             tr_minor_locs = transform.transform(minor_locs)
             tr_major_locs = transform.transform(major_locs)
diff --git a/lib/matplotlib/tests/test_ticker.py b/lib/matplotlib/tests/test_ticker.py
@@ -1873,3 +1873,16 @@ def test_minorticks_on_multi_fig():
 
     assert ax.get_xgridlines()
     assert isinstance(ax.xaxis.get_minor_locator(), mpl.ticker.AutoMinorLocator)
+
+
+def test_locator_reuse():
+    fig = plt.figure()
+    ax = fig.add_subplot(xlim=(.6, .8))
+    loc = mticker.AutoLocator()
+    ax.xaxis.set_major_locator(loc)
+    ax.yaxis.set_major_locator(loc)
+    fig.draw_without_rendering()
+    xticklabels = [l.get_text() for l in ax.get_xticklabels()]
+    yticklabels = [l.get_text() for l in ax.get_yticklabels()]
+    assert xticklabels == ["0.60", "0.65", "0.70", "0.75", "0.80"]
+    assert yticklabels == ["0.0", "0.2", "0.4", "0.6", "0.8", "1.0"]
diff --git a/lib/matplotlib/ticker.py b/lib/matplotlib/ticker.py
@@ -1629,11 +1629,28 @@ def set_params(self, **kwargs):
             str(type(self)))
 
     def __call__(self):
-        """Return the locations of the ticks."""
+        """
+        Return the locations of the ticks.
+
+        The returned locations depend on the locator's axis.  If a locator
+        is used across multiple axises, make sure to (temporarily) set
+        ``locator.axis`` to the correct axis before getting the tick locations.
+        """
         # note: some locators return data limits, other return view limits,
         # hence there is no *one* interface to call self.tick_values.
         raise NotImplementedError('Derived must override')
 
+    def _call_with_axis(self, axis):
+        """
+        Get the tick locations while the locator's axis is temporarily set to *axis*.
+        """
+        current = axis
+        try:
+            self.set_axis(axis)
+            return self()
+        finally:
+            self.set_axis(current)
+
     def raise_if_exceeds(self, locs):
         """
         Log at WARNING level if *locs* is longer than `Locator.MAXTICKS`.
diff --git a/lib/mpl_toolkits/axisartist/axislines.py b/lib/mpl_toolkits/axisartist/axislines.py
@@ -185,11 +185,11 @@ def get_tick_iterators(self, axes):
         angle_normal, angle_tangent = {0: (90, 0), 1: (0, 90)}[self.nth_coord]
 
         major = self.axis.major
-        major_locs = major.locator()
+        major_locs = major.locator._call_with_axis(self.axis)
         major_labels = major.formatter.format_ticks(major_locs)
 
         minor = self.axis.minor
-        minor_locs = minor.locator()
+        minor_locs = minor.locator._call_with_axis(self.axis)
         minor_labels = minor.formatter.format_ticks(minor_locs)
 
         tick_to_axes = self.get_tick_transform(axes) - axes.transAxes
@@ -246,11 +246,11 @@ def get_tick_iterators(self, axes):
         angle_normal, angle_tangent = {0: (90, 0), 1: (0, 90)}[self.nth_coord]
 
         major = self.axis.major
-        major_locs = major.locator()
+        major_locs = major.locator._call_with_axis(self.axis)
         major_labels = major.formatter.format_ticks(major_locs)
 
         minor = self.axis.minor
-        minor_locs = minor.locator()
+        minor_locs = minor.locator._call_with_axis(self.axis)
         minor_labels = minor.formatter.format_ticks(minor_locs)
 
         data_to_axes = axes.transData - axes.transAxes
@@ -351,18 +351,22 @@ def get_gridlines(self, which="major", axis="both"):
             locs = []
             y1, y2 = self.axes.get_ylim()
             if which in ("both", "major"):
-                locs.extend(self.axes.xaxis.major.locator())
+                locs.extend(
+                    self.axes.xaxis.major.locator._call_with_axis(self.axes.xaxis))
             if which in ("both", "minor"):
-                locs.extend(self.axes.xaxis.minor.locator())
+                locs.extend(
+                    self.axes.xaxis.minor.locator._call_with_axis(self.axes.xaxis))
             gridlines.extend([[x, x], [y1, y2]] for x in locs)
 
         if axis in ("both", "y"):
             x1, x2 = self.axes.get_xlim()
             locs = []
             if self.axes.yaxis._major_tick_kw["gridOn"]:
-                locs.extend(self.axes.yaxis.major.locator())
+                locs.extend(
+                    self.axes.yaxis.major.locator._call_with_axis(self.axes.yaxis))
             if self.axes.yaxis._minor_tick_kw["gridOn"]:
-                locs.extend(self.axes.yaxis.minor.locator())
+                locs.extend(
+                    self.axes.yaxis.minor.locator._call_with_axis(self.axis.yaxis))
             gridlines.extend([[x1, x2], [y, y]] for y in locs)
 
         return gridlines
