From 0ff06009554c949f44b196e29dcb99e1a3c5290f Mon Sep 17 00:00:00 2001
From: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com>
Date: Wed, 18 Dec 2024 09:53:18 +0100
Subject: [PATCH] MNT: Warn on using pixel marker for scatter()

Improves on #11460.
---
 lib/matplotlib/axes/_axes.py | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
index f03de3236c8d..c5bac26a28d6 100644
--- a/lib/matplotlib/axes/_axes.py
+++ b/lib/matplotlib/axes/_axes.py
@@ -4938,6 +4938,12 @@ def scatter(self, x, y, s=None, c=None, marker=None, cmap=None, norm=None,
             marker_obj = marker
         else:
             marker_obj = mmarkers.MarkerStyle(marker)
+        if cbook._str_equal(marker_obj.get_marker(), ","):
+            _api.warn_external(
+                "The pixel maker ',' is not supported on scatter(). Fallback "
+                "to a finite-sized square, which is not necessarily 1 pixel in "
+                "size. Use the square marker 's' instead to suppress this warning."
+            )
 
         path = marker_obj.get_path().transformed(
             marker_obj.get_transform())