matplotlib · QianyeSu · Oct 2, 2026 · Oct 2, 2026
diff --git a/lib/matplotlib/axis.py b/lib/matplotlib/axis.py
@@ -1422,25 +1422,41 @@ def _update_ticks(self):
         if (self._tick_group_visible(self._major_tick_kw)
                 and not isinstance(self.get_major_locator(), NullLocator)):
             major_locs = self.get_majorticklocs()
-            major_labels = self.major.formatter.format_ticks(major_locs)
+            major_formatter = self.major.formatter
+            major_labels = major_formatter.format_ticks(major_locs)
+            major_is_custom = (
+                isinstance(major_formatter, mticker.FuncFormatter)
+                and getattr(major_formatter,
+                            "_is_custom_ticklabel_formatter", True))
             major_ticks = self.get_major_ticks(len(major_locs))
             for tick, loc, label in zip(major_ticks, major_locs, major_labels):
                 tick.update_position(loc)
                 tick.label1.set_text(label)
                 tick.label2.set_text(label)
+                # Custom formatters can produce labels with different
+                # ascenders, so let Text use a common line box for them.
+                tick.label1._is_ticklabel = major_is_custom
+                tick.label2._is_ticklabel = major_is_custom
         else:
             major_ticks = []
 
         # Check if minor ticks should be computed.
         if (self._tick_group_visible(self._minor_tick_kw)
                 and not isinstance(self.get_minor_locator(), NullLocator)):
             minor_locs = self.get_minorticklocs()
-            minor_labels = self.minor.formatter.format_ticks(minor_locs)
+            minor_formatter = self.minor.formatter
+            minor_labels = minor_formatter.format_ticks(minor_locs)
+            minor_is_custom = (
+                isinstance(minor_formatter, mticker.FuncFormatter)
+                and getattr(minor_formatter,
+                            "_is_custom_ticklabel_formatter", True))
             minor_ticks = self.get_minor_ticks(len(minor_locs))
             for tick, loc, label in zip(minor_ticks, minor_locs, minor_labels):
                 tick.update_position(loc)
                 tick.label1.set_text(label)
                 tick.label2.set_text(label)
+                tick.label1._is_ticklabel = minor_is_custom
+                tick.label2._is_ticklabel = minor_is_custom
         else:
             minor_ticks = []
 
@@ -2345,6 +2361,10 @@ def set_ticklabels(self, labels, *, minor=False, fontdict=None, **kwargs):
             tickd = {loc: lab for loc, lab in zip(fixed_locator.locs, labels)}
             func = functools.partial(self._format_with_dict, tickd)
             formatter = mticker.FuncFormatter(func)
+            # ``set_ticklabels`` uses a ``FuncFormatter`` internally, but
+            # these are fixed labels rather than user-defined formatting.
+            # Keep them on the existing text-layout path.
+            formatter._is_custom_ticklabel_formatter = False
         else:
             _api.warn_external(
                  "set_ticklabels() should only be used with a fixed number of "

diff --git a/lib/matplotlib/tests/baseline_images/test_axes/bar_tick_label_multiple.png b/lib/matplotlib/tests/baseline_images/test_axes/bar_tick_label_multiple.png
diff --git a/...tests/baseline_images/test_axes/bar_tick_label_multiple_old_label_alignment.png b/...tests/baseline_images/test_axes/bar_tick_label_multiple_old_label_alignment.png
diff --git a/lib/matplotlib/tests/baseline_images/test_axes/bar_tick_label_single.png b/lib/matplotlib/tests/baseline_images/test_axes/bar_tick_label_single.png
diff --git a/lib/matplotlib/tests/baseline_images/test_axes/boxplot.png b/lib/matplotlib/tests/baseline_images/test_axes/boxplot.png
diff --git a/...matplotlib/tests/baseline_images/test_axes/boxplot_autorange_false_whiskers.png b/...matplotlib/tests/baseline_images/test_axes/boxplot_autorange_false_whiskers.png
diff --git a/lib/matplotlib/tests/baseline_images/test_axes/boxplot_autorange_true_whiskers.png b/lib/matplotlib/tests/baseline_images/test_axes/boxplot_autorange_true_whiskers.png
diff --git a/lib/matplotlib/tests/baseline_images/test_axes/boxplot_custom_capwidths.png b/lib/matplotlib/tests/baseline_images/test_axes/boxplot_custom_capwidths.png
diff --git a/lib/matplotlib/tests/baseline_images/test_axes/bxp_baseline.png b/lib/matplotlib/tests/baseline_images/test_axes/bxp_baseline.png
diff --git a/lib/matplotlib/tests/baseline_images/test_axes/bxp_custom_capwidth.png b/lib/matplotlib/tests/baseline_images/test_axes/bxp_custom_capwidth.png
diff --git a/lib/matplotlib/tests/baseline_images/test_axes/bxp_custom_capwidths.png b/lib/matplotlib/tests/baseline_images/test_axes/bxp_custom_capwidths.png
diff --git a/lib/matplotlib/tests/baseline_images/test_axes/bxp_percentilewhis.png b/lib/matplotlib/tests/baseline_images/test_axes/bxp_percentilewhis.png
diff --git a/lib/matplotlib/tests/baseline_images/test_axes/bxp_rangewhis.png b/lib/matplotlib/tests/baseline_images/test_axes/bxp_rangewhis.png
diff --git a/lib/matplotlib/tests/baseline_images/test_axes/bxp_with_xlabels.png b/lib/matplotlib/tests/baseline_images/test_axes/bxp_with_xlabels.png
diff --git a/lib/matplotlib/tests/baseline_images/test_axes/extent_units.png b/lib/matplotlib/tests/baseline_images/test_axes/extent_units.png
diff --git a/lib/matplotlib/tests/baseline_images/test_axes/grouped_bar.png b/lib/matplotlib/tests/baseline_images/test_axes/grouped_bar.png
diff --git a/lib/matplotlib/tests/baseline_images/test_axes/set_get_ticklabels.png b/lib/matplotlib/tests/baseline_images/test_axes/set_get_ticklabels.png
diff --git a/lib/matplotlib/tests/baseline_images/test_axes/twin_axis_locators_formatters.png b/lib/matplotlib/tests/baseline_images/test_axes/twin_axis_locators_formatters.png
diff --git a/lib/matplotlib/tests/baseline_images/test_colors/boundarynorm_and_colorbar.png b/lib/matplotlib/tests/baseline_images/test_colors/boundarynorm_and_colorbar.png
diff --git a/lib/matplotlib/tests/baseline_images/test_figure/test_subfigure.png b/lib/matplotlib/tests/baseline_images/test_figure/test_subfigure.png
diff --git a/lib/matplotlib/tests/test_text.py b/lib/matplotlib/tests/test_text.py
@@ -188,6 +188,21 @@ def draw_box(ax, tt):
     ax.text(1.2, 0.1, 'Bot align, rot20', color='C2')
 
 
+def test_top_aligned_text_has_consistent_baseline():
+    fig, ax = plt.subplots(figsize=(.5, .5), layout="constrained")
+    ax.set_yticks([])
+    ax.set_xlim(-2, 3)
+    ax.set_xticks([0, 1])
+    ax.xaxis.set_major_formatter(
+        lambda x, pos: "pol." if x == 0 else str(int(x)))
+
+    fig.canvas.draw()
+    bboxes = [label.get_window_extent() for label in ax.get_xticklabels()]
+
+    # Labels with different ascenders must still share a baseline.
+    assert_almost_equal(bboxes[0].y0, bboxes[1].y0)
+
+
 @image_comparison(['antialiased.png'], style='mpl20')
 def test_antialiasing():
     mpl.rcParams['text.antialiased'] = False  # Passed arguments should override.

diff --git a/lib/matplotlib/text.py b/lib/matplotlib/text.py
@@ -485,6 +485,22 @@ def _get_layout(self, renderer):
             min_ascent = h - min_descent
             line_gap = 0
 
+        if (getattr(self, "_is_ticklabel", False)
+                and self._verticalalignment == "top"
+                and self.get_rotation() == 0
+                and len(lines) == 1):
+            # Top-aligned single-line text should use a common line box.  In
+            # particular, this keeps the baselines of tick labels with
+            # different ascenders aligned (e.g. ``"pol."`` and ``"1"``).
+            # The font tables alone do not necessarily include the full
+            # ascent of the glyphs used by the renderer.
+            _, lp_h, lp_d = _get_text_metrics_with_cache(
+                renderer, "lp", self._fontproperties,
+                ismath="TeX" if self.get_usetex() else False,
+                dpi=dpi)
+            min_ascent = max(min_ascent, lp_h - lp_d)
+            min_descent = max(min_descent, lp_d)
+
         # Don't increase text height too much if it's not multiple lines.
         if len(lines) == 1:
             line_gap = 0

diff --git a/lib/mpl_toolkits/mplot3d/tests/baseline_images/test_axes3d/minor_ticks.png b/lib/mpl_toolkits/mplot3d/tests/baseline_images/test_axes3d/minor_ticks.png