Backport PR matplotlib#32221: Qt IconEngine: Use a device pixel ratio of 1 when high-DPI pixmaps are disabled

Author: timhoffm

lib/matplotlib/backends/backend_qt.py

@@ -720,7 +720,12 @@ def pixmap(self, size, mode, state):
 
     def _devicePixelRatio(self):
         """Return the current device pixel ratio for the toolbar, defaulting to 1."""
-        return (self.toolbar.devicePixelRatioF() or 1) if self.toolbar else 1
+        use_high_dpi_pixmaps = True
+        if hasattr(QtCore.Qt.ApplicationAttribute, "AA_UseHighDpiPixmaps"):
+            app = QtWidgets.QApplication.instance()
+            use_high_dpi_pixmaps = app.testAttribute(QtCore.Qt.AA_UseHighDpiPixmaps)
+        toolbar_dpr = (self.toolbar.devicePixelRatioF() or 1) if self.toolbar else 1
+        return toolbar_dpr if use_high_dpi_pixmaps else 1
 
     def _create_pixmap_from_svg(self, svg_path, size):
         """Create a pixmap from SVG with proper scaling and dark mode support."""