BUG: Fix relim() to support Collection artists (scatter, etc.) relim() previously skipped Collection instances entirely. Two issues: 1. add_collection() did not call collection._set_in_autoscale(True), unlike add_line(), add_patch(), and add_image(). This caused relim() to skip collections via the _get_in_autoscale() check. 2. relim() had no handling for Collection instances. Added an elif branch that calls get_datalim() and update_datalim(), mirroring the logic already used in add_collection(). Closes #30859

tinezivic · tinezivic · commit 07127b686398 · 2026-04-19T14:58:19.000+02:00
diff --git a/doc/api/next_api_changes/behavior/31530-TZ.rst b/doc/api/next_api_changes/behavior/31530-TZ.rst
@@ -0,0 +1,6 @@
+``relim()`` now accounts for Collection artists
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Previously, `~.axes.Axes.relim` did not recalculate data limits for
+`.Collection` artists (e.g. those created by `~.axes.Axes.scatter`).
+Calling ``ax.relim()`` followed by ``ax.autoscale_view()`` now correctly
+includes scatter plots and other collections in the axes limits.
diff --git a/lib/matplotlib/axes/_base.py b/lib/matplotlib/axes/_base.py
@@ -2434,6 +2434,7 @@ def add_collection(self, collection, autolim=True):
                 self._request_autoscale_view()
 
         self.stale = True
+        collection._set_in_autoscale(True)
         return collection
 
     def add_image(self, image):
@@ -2638,15 +2639,11 @@ def relim(self, visible_only=False):
         """
         Recompute the data limits based on current artists.
 
-        At present, `.Collection` instances are not supported.
-
         Parameters
         ----------
         visible_only : bool, default: False
             Whether to exclude invisible artists.
         """
-        # Collections are deliberately not supported (yet); see
-        # the TODO note in artists.py.
         self.dataLim.ignore(True)
         self.dataLim.set_points(mtransforms.Bbox.null().get_points())
         self.ignore_existing_data_limits = True
@@ -2661,6 +2658,23 @@ def relim(self, visible_only=False):
                     self._update_patch_limits(artist)
                 elif isinstance(artist, mimage.AxesImage):
                     self._update_image_limits(artist)
+                elif isinstance(artist, mcoll.Collection):
+                    datalim = artist.get_datalim(self.transData)
+                    points = datalim.get_points()
+                    if not np.isinf(datalim.minpos).all():
+                        points = np.concatenate([points,
+                                                 [datalim.minpos]])
+                    x_is_data, y_is_data = (
+                        artist.get_transform()
+                        .contains_branch_separately(self.transData))
+                    ox_is_data, oy_is_data = (
+                        artist.get_offset_transform()
+                        .contains_branch_separately(self.transData))
+                    self.update_datalim(
+                        points,
+                        updatex=x_is_data or ox_is_data,
+                        updatey=y_is_data or oy_is_data,
+                    )
 
     def update_datalim(self, xys, updatex=True, updatey=True):
         """
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -6511,6 +6511,37 @@ def test_relim_visible_only():
     assert ax.get_ylim() == y1
 
 
+def test_relim_collection():
+    fig, ax = plt.subplots()
+    sc = ax.scatter([1, 2, 3], [4, 5, 6])
+    ax.relim()
+    ax.autoscale_view()
+    xlim = ax.get_xlim()
+    ylim = ax.get_ylim()
+    assert xlim[0] <= 1 and xlim[1] >= 3
+    assert ylim[0] <= 4 and ylim[1] >= 6
+
+    # After updating offsets, relim should track the new data.
+    sc.set_offsets([[10, 20], [30, 40]])
+    ax.relim()
+    ax.autoscale_view()
+    xlim = ax.get_xlim()
+    ylim = ax.get_ylim()
+    assert xlim[0] <= 10 and xlim[1] >= 30
+    assert ylim[0] <= 20 and ylim[1] >= 40
+
+    # visible_only=True should ignore hidden collections.
+    line, = ax.plot([0, 1], [0, 1])
+    sc.set_visible(False)
+    ax.relim(visible_only=True)
+    ax.autoscale_view()
+    xlim = ax.get_xlim()
+    ylim = ax.get_ylim()
+    # With scatter hidden, limits should be driven by the line only.
+    assert xlim[1] < 10
+    assert ylim[1] < 10
+
+
 def test_text_labelsize():
     """
     tests for issue #1172
