TST/BUG: Fix _datalim_only semantics and add user-facing relim test

tinezivic · tinezivic · commit f90c147dd486 · 2026-04-21T06:54:31.000+02:00
_set_in_autoscale(True) must not be called for collections added with
autolim='_datalim_only' — that sentinel means 'update datalim once but
do not enter the autoscale/relim system'. Previously, because the call
was outside the if autolim: block, bool('_datalim_only') == True meant
3D collections inadvertently got _in_autoscale=True. Fixed by gating
the call on autolim != '_datalim_only', consistent with the existing
_request_autoscale_view guard directly below.

Also add test_relim_collection_autoscale_view: an end-to-end regression
that checks ax.get_xlim()/get_ylim() after relim()+autoscale_view(),
matching the exact user-facing scenario from GH#30859.
diff --git a/lib/matplotlib/axes/_base.py b/lib/matplotlib/axes/_base.py
@@ -2418,7 +2418,8 @@ def add_collection(self, collection, autolim=True):
             collection.set_clip_path(self.patch)
 
         if autolim:
-            collection._set_in_autoscale(True)
+            if autolim != "_datalim_only":
+                collection._set_in_autoscale(True)
             # Make sure viewLim is not stale (mostly to match
             # pre-lazy-autoscale behavior, which is not really better).
             self._unstale_viewLim()
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -6568,6 +6568,22 @@ def test_relim_collection_log_scale():
     assert_allclose(ax.dataLim.minpos, expected.minpos)
 
 
+def test_relim_collection_autoscale_view():
+    # GH#30859 - end-to-end: after set_offsets(), relim() + autoscale_view()
+    # must update the visible axis limits, not just dataLim.
+    fig, ax = plt.subplots()
+    sc = ax.scatter([], [])
+    xs = np.linspace(0, 10, 50)
+    sc.set_offsets(np.column_stack((xs, np.sin(xs))))
+    ax.relim()
+    ax.autoscale_view()
+    xlim = ax.get_xlim()
+    ylim = ax.get_ylim()
+    # autoscale_view adds a margin, so limits should comfortably contain data
+    assert xlim[0] <= 0 and xlim[1] >= 10, f"xlim should contain [0, 10], got {xlim}"
+    assert ylim[0] <= -1 and ylim[1] >= 1, f"ylim should contain [-1, 1], got {ylim}"
+
+
 def test_text_labelsize():
     """
     tests for issue #1172
