From 7b34fc5c0bcbcb2d637b9d11cf1f9caaf0298e90 Mon Sep 17 00:00:00 2001
From: Thomas A Caswell <tcaswell@gmail.com>
Date: Thu, 17 Feb 2022 23:09:15 -0500
Subject: [PATCH] Backport PR #22476: FIX: Include (0, 0) offsets in scatter
 autoscaling

---
 lib/matplotlib/collections.py            | 32 ++++++++++++------------
 lib/matplotlib/tests/test_collections.py | 16 ++++++++++++
 2 files changed, 32 insertions(+), 16 deletions(-)

diff --git a/lib/matplotlib/collections.py b/lib/matplotlib/collections.py
index e7e630475e0d..e45d8527a83c 100644
--- a/lib/matplotlib/collections.py
+++ b/lib/matplotlib/collections.py
@@ -268,8 +268,8 @@ def get_datalim(self, transData):
 
         transform = self.get_transform()
         transOffset = self.get_offset_transform()
-        hasOffsets = np.any(self._offsets)  # True if any non-zero offsets
-        if hasOffsets and not transOffset.contains_branch(transData):
+        if not (isinstance(transOffset, transforms.IdentityTransform)
+                or transOffset.contains_branch(transData)):
             # if there are offsets but in some coords other than data,
             # then don't use them for autoscaling.
             return transforms.Bbox.null()
@@ -299,20 +299,20 @@ def get_datalim(self, transData):
                     self.get_transforms(),
                     transOffset.transform_non_affine(offsets),
                     transOffset.get_affine().frozen())
-            if hasOffsets:
-                # this is for collections that have their paths (shapes)
-                # in physical, axes-relative, or figure-relative units
-                # (i.e. like scatter). We can't uniquely set limits based on
-                # those shapes, so we just set the limits based on their
-                # location.
-
-                offsets = (transOffset - transData).transform(offsets)
-                # note A-B means A B^{-1}
-                offsets = np.ma.masked_invalid(offsets)
-                if not offsets.mask.all():
-                    bbox = transforms.Bbox.null()
-                    bbox.update_from_data_xy(offsets)
-                    return bbox
+
+            # this is for collections that have their paths (shapes)
+            # in physical, axes-relative, or figure-relative units
+            # (i.e. like scatter). We can't uniquely set limits based on
+            # those shapes, so we just set the limits based on their
+            # location.
+
+            offsets = (transOffset - transData).transform(offsets)
+            # note A-B means A B^{-1}
+            offsets = np.ma.masked_invalid(offsets)
+            if not offsets.mask.all():
+                bbox = transforms.Bbox.null()
+                bbox.update_from_data_xy(offsets)
+                return bbox
         return transforms.Bbox.null()
 
     def get_window_extent(self, renderer):
diff --git a/lib/matplotlib/tests/test_collections.py b/lib/matplotlib/tests/test_collections.py
index fb7dade2b459..583d1489a668 100644
--- a/lib/matplotlib/tests/test_collections.py
+++ b/lib/matplotlib/tests/test_collections.py
@@ -715,6 +715,22 @@ def test_singleton_autolim():
     np.testing.assert_allclose(ax.get_xlim(), [-0.06, 0.06])
 
 
+@pytest.mark.parametrize("transform, expected", [
+    ("transData", (-0.5, 3.5)),
+    ("transAxes", (2.8, 3.2)),
+])
+def test_autolim_with_zeros(transform, expected):
+    # 1) Test that a scatter at (0, 0) data coordinates contributes to
+    # autoscaling even though any(offsets) would be False in that situation.
+    # 2) Test that specifying transAxes for the transform does not contribute
+    # to the autoscaling.
+    fig, ax = plt.subplots()
+    ax.scatter(0, 0, transform=getattr(ax, transform))
+    ax.scatter(3, 3)
+    np.testing.assert_allclose(ax.get_ylim(), expected)
+    np.testing.assert_allclose(ax.get_xlim(), expected)
+
+
 @pytest.mark.parametrize('flat_ref, kwargs', [
     (True, {}),
     (False, {}),