Remove reference to old Tk/Windows bug.

anntzer · anntzer · commit 5a18309f6fe8 · 2019-06-26T10:24:28.000+02:00
See patch.

At least I can't repro it on Windows, and you'd expect it to be
semi-regularly reported on the tracker if it still occurred.

In the example, don't bother calling `root.destroy()`, as `root.quit()`
already handles the destroying (both on Linux and Windows, an additional
call to `root.destroy()` results in "can't invoke "destroy" command:
application has been destroyed").
diff --git a/examples/user_interfaces/embedding_in_tk_sgskip.py b/examples/user_interfaces/embedding_in_tk_sgskip.py
@@ -39,17 +39,7 @@ def on_key_press(event):
 
 canvas.mpl_connect("key_press_event", on_key_press)
 
-
-def _quit():
-    root.quit()  # Stops mainloop.
-    # The following is necessary on Windows to prevent
-    # Fatal Python Error: PyEval_RestoreThread: NULL tstate
-    root.destroy()
-
-
-button = tkinter.Button(master=root, text="Quit", command=_quit)
+button = tkinter.Button(master=root, text="Quit", command=root.quit)
 button.pack(side=tkinter.BOTTOM)
 
 tkinter.mainloop()
-# If you put root.destroy() here, it will cause an error if the window is
-# closed with the window manager.
diff --git a/lib/matplotlib/backends/_backend_tk.py b/lib/matplotlib/backends/_backend_tk.py
@@ -465,10 +465,6 @@ def resize(self, width, height):
             self.toolbar.configure(width=width)
 
     def show(self):
-        """
-        this function doesn't segfault but causes the
-        PyEval_RestoreThread: NULL state bug on win32
-        """
         with _restore_foreground_window_at_end():
             if not self._shown:
                 def destroy(*args):
