From eaaee4ea6e3fca68ffbc678428451f5082f8714c Mon Sep 17 00:00:00 2001
From: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com>
Date: Thu, 6 Jan 2022 23:32:24 +0100
Subject: [PATCH] Fix loading user-defined icons for Qt plot window

---
 lib/matplotlib/backends/backend_qt.py | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/lib/matplotlib/backends/backend_qt.py b/lib/matplotlib/backends/backend_qt.py
index c55937a019ea..7de28f7b0541 100644
--- a/lib/matplotlib/backends/backend_qt.py
+++ b/lib/matplotlib/backends/backend_qt.py
@@ -682,8 +682,14 @@ def _icon(self, name):
         Construct a `.QIcon` from an image file *name*, including the extension
         and relative to Matplotlib's "images" data directory.
         """
-        name = name.replace('.png', '_large.png')
-        pm = QtGui.QPixmap(str(cbook._get_data_path('images', name)))
+        # use a high-resolution icon with suffix '_large' if available
+        # note: user-provided icons may not have '_large' versions
+        path_regular = cbook._get_data_path('images', name)
+        path_large = path_regular.with_name(
+            path_regular.name.replace('.png', '_large.png'))
+        filename = str(path_large if path_large.exists() else path_regular)
+
+        pm = QtGui.QPixmap(filename)
         _setDevicePixelRatio(pm, _devicePixelRatioF(self))
         if self.palette().color(self.backgroundRole()).value() < 128:
             icon_color = self.palette().color(self.foregroundRole())