BUG: Fix Windows subprocess timeouts with CREATE_NO_WINDOW flag (#30886)

sanrishi · timhoffm · web-flow · commit a326d0700a46 · 2026-01-08T15:34:09.000-05:00
* Added CREATE_NO_WINDOW flag on Windows to prevent console window overhead

* Fixed Ruff Failed check error

* Fixed Ruff error

* Update lib/matplotlib/testing/__init__.py

Co-authored-by: Tim Hoffmann &lt;2836374+timhoffm@users.noreply.github.com&gt;

---------

Co-authored-by: Tim Hoffmann &lt;2836374+timhoffm@users.noreply.github.com&gt;
diff --git a/lib/matplotlib/testing/__init__.py b/lib/matplotlib/testing/__init__.py
@@ -92,6 +92,13 @@ def subprocess_run_for_testing(command, env=None, timeout=60, stdout=None,
     """
     if capture_output:
         stdout = stderr = subprocess.PIPE
+    # Add CREATE_NO_WINDOW flag on Windows to prevent console window overhead
+    # This is added in an attempt to fix flaky timeouts of subprocesses on Windows
+    if sys.platform == 'win32':
+        if 'creationflags' not in kwargs:
+            kwargs['creationflags'] = subprocess.CREATE_NO_WINDOW
+        else:
+            kwargs['creationflags'] |= subprocess.CREATE_NO_WINDOW
     try:
         proc = subprocess.run(
             command, env=env,
