matplotlib · AlextheGreat1509 · Mar 28, 2023 · Mar 30, 2023 · Mar 30, 2023 · Mar 30, 2023
diff --git a/lib/matplotlib/axes/_base.py b/lib/matplotlib/axes/_base.py
@@ -2990,6 +2990,16 @@ def _update_title_position(self, renderer):
             x, _ = title.get_position()
             title.set_position((x, ymax))
 
+        # Align bboxes of grouped axes to highest in group
+        grouped_axs = self.figure._align_label_groups['title'].get_siblings(self)
+        bb_ymax = None
+        ax_max = None
+        for ax in grouped_axs:
+            if bb_ymax is None or ax.bbox.ymax > bb_ymax:
+                bb_ymax = ax.bbox.ymax
+                ax_max = ax
+        self.bbox = ax_max.bbox
+
     # Drawing
     @martist.allow_rasterization
     def draw(self, renderer):

diff --git a/lib/matplotlib/figure.py b/lib/matplotlib/figure.py
@@ -183,10 +183,11 @@ def __init__(self, **kwargs):
         self._supxlabel = None
         self._supylabel = None
 
-        # groupers to keep track of x and y labels we want to align.
-        # see self.align_xlabels and self.align_ylabels and
+        # groupers to keep track of x, y and title labels we want to align.
+        # see self.align_xlabels, self.align_ylabels, self.align_titles and
         # axis._get_tick_boxes_siblings
-        self._align_label_groups = {"x": cbook.Grouper(), "y": cbook.Grouper()}
+        self._align_label_groups = {"x": cbook.Grouper(), "y": cbook.Grouper(),
+                                    "title": cbook.Grouper()}
 
         self.figure = self
         self._localaxes = []  # track all axes
@@ -1327,6 +1328,68 @@ def subplots_adjust(self, left=None, bottom=None, right=None, top=None,
                 ax._set_position(ax.get_subplotspec().get_position(self))
         self.stale = True
 
+    def align_titles(self, axs=None):
+        """
+        Align the titles of subplots in the same subplot column if title
+        alignment is being done automatically (i.e. the title position is
+        not manually set).
+
+        Alignment persists for draw events after this is called.
+
+        If the title is on the top,
+        it is aligned with titles on Axes with the same top-most row.
+
+        Parameters
+        ----------
+        axs : list of `~matplotlib.axes.Axes`
+            Optional list of (or `~numpy.ndarray`) `~matplotlib.axes.Axes`
+            to align the titles.
+            Default is to align all titles on the figure.
+
+        See Also
+        --------
+        matplotlib.figure.Figure.align_ylabels
+        matplotlib.figure.Figure.align_xlabels
+        matplotlib.figure.Figure.align_labels
+
+        Notes
+        -----
+        This assumes that ``axs`` are from the same `.GridSpec`, so that
+        their `.SubplotSpec` positions correspond to figure positions.
+
+        Examples
+        --------
+        Example with aligned titles on multiple rows::
+
+            fig, axs = plt.subplots(2, 2,
+                            subplot_kw={"xlabel": "x", "ylabel": "",
+                                        "title": "Title"})
+            axs[0][0].imshow(plt.np.zeros((5, 3)))
+            axs[0][1].imshow(plt.np.zeros((3, 5)))
+            axs[1][0].imshow(plt.np.zeros((2, 1)))
+            axs[1][1].imshow(plt.np.zeros((1, 2)))
+
+            axs[0][1].set_title('Title2', loc="left")
+            fig.align_titles()
+        """
+        if axs is None:
+            axs = self.axes
+        axs = [ax for ax in np.ravel(axs) if ax.get_subplotspec() is not None]
+        locs = ['left', 'center', 'right']
+        for ax in axs:
+            for loc in locs:
+                if ax.get_title(loc=loc):
+                    rowspan = ax.get_subplotspec().rowspan
+                    for axc in axs:
+                        rowspanc = axc.get_subplotspec().rowspan
+                        if rowspan.start == rowspanc.start or \
+                                rowspan.stop == rowspanc.stop:
+                            self._align_label_groups['title'].join(ax, axc)
+
+        # Fixes the issue that the bbox is too small to fit the aligned
+        # title when saving the figure
+        self.canvas.draw_idle()
+
     def align_xlabels(self, axs=None):
         """
         Align the xlabels of subplots in the same subplot column if label

diff --git a/lib/matplotlib/tests/test_figure.py b/lib/matplotlib/tests/test_figure.py
@@ -11,6 +11,7 @@
 import numpy as np
 import pytest
 from PIL import Image
+from matplotlib.testing.compare import compare_images
 
 import matplotlib as mpl
 from matplotlib import gridspec
@@ -102,6 +103,37 @@ def test_align_labels_stray_axes():
     np.testing.assert_allclose(yn[::2], yn[1::2])
 
 
+## TODO add image comparison
+@image_comparison(['figure_align_titles'], extensions=['png', 'svg'],
+                   tol=0 if platform.machine() == 'x86_64' else 0.01, style='mpl20')
+def test_align_titles():
+    fig, axs = plt.subplots(2, 2,
+                            subplot_kw={"xlabel": "x", "ylabel": "",
+                                        "title": "Title"}, layout="constrained")
+    axs[0][0].imshow(plt.np.zeros((5, 3)))
+    axs[0][1].imshow(plt.np.zeros((3, 5)))
+    axs[1][0].imshow(plt.np.zeros((2, 1)))
+    axs[1][1].imshow(plt.np.zeros((1, 2)))
+
+    axs[0][1].set_title('Title2', loc="left")
+    fig.align_titles()
+
+
+## TODO add image comparison
+@image_comparison(['figure_align_titles_param'], extensions=['png', 'svg'],
+                   tol=0 if platform.machine() == 'x86_64' else 0.01, style='mpl20')
+def test_align_titles_param():
+    fig, axs = plt.subplots(2, 2,
+                            subplot_kw={"xlabel": "x", "ylabel": "",
+                                        "title": "t"}, layout="constrained")
+    axs[0][0].imshow(plt.np.zeros((3, 5)))
+    axs[0][1].imshow(plt.np.zeros((5, 3)))
+    axs[1][0].imshow(plt.np.zeros((2, 1)))
+    axs[1][1].imshow(plt.np.zeros((1, 2)))
+
+    fig.align_titles([axs[0][0], axs[0][1]])
+
+
 def test_figure_label():
     # pyplot figure creation, selection, and closing with label/number/instance
     plt.close('all')