BUG: Preserve autolim=False semantics for Collection relim support

tinezivic · tinezivic · commit 3da28af5d6dc · 2026-04-20T03:47:37.000+02:00
_set_in_autoscale(True) was set unconditionally in add_collection(), outside the 'if autolim:' block. This meant that any collection added with autolim=False would still be picked up by relim() later. Fix: move _set_in_autoscale(True) inside the 'if autolim:' block so that relim() only considers collections that explicitly opted in. Add two regression tests: - test_relim_collection_autolim_false: verifies that a collection added with autolim=False does not affect limits after relim(). - test_relim_collection_log_scale: verifies that relim() + autoscale_view() works correctly for a Collection on log-scaled axes (exercises the minpos path). Closes #30859
diff --git a/lib/matplotlib/axes/_base.py b/lib/matplotlib/axes/_base.py
@@ -2432,9 +2432,12 @@ def add_collection(self, collection, autolim=True):
             )
             if autolim != "_datalim_only":
                 self._request_autoscale_view()
+            # Mark collection as participating in relim() only when autolim
+            # is enabled.  If autolim=False the caller explicitly opted out,
+            # so relim() must not pick this collection up later.
+            collection._set_in_autoscale(True)
 
         self.stale = True
-        collection._set_in_autoscale(True)
         return collection
 
     def add_image(self, image):
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -6542,6 +6542,40 @@ def test_relim_collection():
     assert ylim[1] < 10
 
 
+def test_relim_collection_autolim_false():
+    # GH#30859 - Collection added with autolim=False must not participate
+    # in relim() later.
+    import matplotlib.collections as mcollections
+    fig, ax = plt.subplots()
+    ax.set_xlim(0, 1)
+    ax.set_ylim(0, 1)
+    # Build a collection far outside current limits and add it with autolim=False.
+    sc = mcollections.PathCollection([])
+    sc.set_offsets([[100, 200], [300, 400]])
+    ax.add_collection(sc, autolim=False)
+    ax.relim()
+    ax.autoscale_view()
+    # Limits must remain unchanged because autolim=False was requested.
+    assert ax.get_xlim() == (0, 1)
+    assert ax.get_ylim() == (0, 1)
+
+
+def test_relim_collection_log_scale():
+    # GH#30859 - relim() for Collection on a log-scaled axis should
+    # correctly pick up minpos so that log scaling works properly.
+    fig, ax = plt.subplots()
+    ax.set_xscale('log')
+    ax.set_yscale('log')
+    sc = ax.scatter([1e-3, 1e-2, 1e-1], [1e1, 1e2, 1e3])
+    sc.set_offsets([[1e1, 1e4], [1e2, 1e5]])
+    ax.relim()
+    ax.autoscale_view()
+    xlim = ax.get_xlim()
+    ylim = ax.get_ylim()
+    assert xlim[0] <= 1e1 and xlim[1] >= 1e2
+    assert ylim[0] <= 1e4 and ylim[1] >= 1e5
+
+
 def test_text_labelsize():
     """
     tests for issue #1172
