Merge pull request matplotlib#28734 from rcomer/compressed-suptitle

doc/api/next_api_changes/behavior/28734-REC.rst

@@ -0,0 +1,7 @@
+``suptitle`` in compressed layout
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Compressed layout now automatically positions the `~.Figure.suptitle` just
+above the top row of axes.  To keep this title in its previous position,
+either pass ``in_layout=False`` or explicitly set ``y=0.98`` in the
+`~.Figure.suptitle` call.

lib/matplotlib/_constrained_layout.py

@@ -140,6 +140,13 @@ def do_constrained_layout(fig, h_pad, w_pad,
                                     w_pad=w_pad, hspace=hspace, wspace=wspace)
                 else:
                     _api.warn_external(warn_collapsed)
+
+                if ((suptitle := fig._suptitle) is not None and
+                        suptitle.get_in_layout() and suptitle._autopos):
+                    x, _ = suptitle.get_position()
+                    suptitle.set_position(
+                        (x, layoutgrids[fig].get_inner_bbox().y1 + h_pad))
+                    suptitle.set_verticalalignment('bottom')
         else:
             _api.warn_external(warn_collapsed)
         reset_margins(layoutgrids, fig)

lib/matplotlib/tests/test_constrainedlayout.py

@@ -662,6 +662,30 @@ def test_compressed1():
     np.testing.assert_allclose(pos.y0, 0.1934, atol=1e-3)
 
 
+def test_compressed_suptitle():
+    fig, (ax0, ax1) = plt.subplots(
+        nrows=2, figsize=(4, 10), layout="compressed",
+        gridspec_kw={"height_ratios": (1 / 4, 3 / 4), "hspace": 0})
+
+    ax0.axis("equal")
+    ax0.set_box_aspect(1/3)
+
+    ax1.axis("equal")
+    ax1.set_box_aspect(1)
+
+    title = fig.suptitle("Title")
+    fig.draw_without_rendering()
+    assert title.get_position()[1] == pytest.approx(0.7457, abs=1e-3)
+
+    title = fig.suptitle("Title", y=0.98)
+    fig.draw_without_rendering()
+    assert title.get_position()[1] == 0.98
+
+    title = fig.suptitle("Title", in_layout=False)
+    fig.draw_without_rendering()
+    assert title.get_position()[1] == 0.98
+
+
 @pytest.mark.parametrize('arg, state', [
     (True, True),
     (False, False),