From 575a2469aec02452ec5c7b33acbc113121c4cea7 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..b29531d260c0 100644
--- a/lib/matplotlib/axes/_axes.py
+++ b/lib/matplotlib/axes/_axes.py
@@ -4933,6 +4933,12 @@ def scatter(self, x, y, s=None, c=None, marker=None, cmap=None, norm=None,
         # load default marker from rcParams
         if marker is None:
             marker = mpl.rcParams['scatter.marker']
+        if marker == ",":
+            _api.warn_external(
+                "The pixel maker ',' is not supported on scatter(). Fallback "
+                "to a finite-sized square, which is necessarily 1 pixel in "
+                "size. Use the square marker 's' to suppress this warning."
+            )
 
         if isinstance(marker, mmarkers.MarkerStyle):
             marker_obj = marker