Merge pull request matplotlib#28015 from meeseeksmachine/auto-backport-of-pr-27955-on-v3.8.x

Backport PR matplotlib#27955 on branch v3.8.x (Add a draw during show for macos backend)

Author: QuLogic

lib/matplotlib/backends/backend_macosx.py

@@ -179,6 +179,8 @@ def start_main_loop(cls):
             _macosx.show()
 
     def show(self):
+        if self.canvas.figure.stale:
+            self.canvas.draw_idle()
         if not self._shown:
             self._show()
             self._shown = True