Merge pull request #24178 from QuLogic/pypy-threads

oscargus · web-flow · commit 9bcdd604ab9c · 2022-10-15T16:35:24.000+02:00
Fall back to Python-level Thread for GUI warning
diff --git a/lib/matplotlib/pyplot.py b/lib/matplotlib/pyplot.py
@@ -332,11 +332,21 @@ def draw_if_interactive():
 
 
 def _warn_if_gui_out_of_main_thread():
-    # This compares native thread ids because even if python-level Thread
-    # objects match, the underlying OS thread (which is what really matters)
-    # may be different on Python implementations with green threads.
-    if (_get_required_interactive_framework(_get_backend_mod()) and
-            threading.get_native_id() != threading.main_thread().native_id):
+    warn = False
+    if _get_required_interactive_framework(_get_backend_mod()):
+        if hasattr(threading, 'get_native_id'):
+            # This compares native thread ids because even if Python-level
+            # Thread objects match, the underlying OS thread (which is what
+            # really matters) may be different on Python implementations with
+            # green threads.
+            if threading.get_native_id() != threading.main_thread().native_id:
+                warn = True
+        else:
+            # Fall back to Python-level Thread if native IDs are unavailable,
+            # mainly for PyPy.
+            if threading.current_thread() is not threading.main_thread():
+                warn = True
+    if warn:
         _api.warn_external(
             "Starting a Matplotlib GUI outside of the main thread will likely "
             "fail.")
