fix FigureManagerTk close behavior if embedded in Tk App

lib/matplotlib/backends/_backend_tk.py

@@ -398,6 +398,8 @@ class FigureManagerTk(FigureManagerBase):
         The tk.Window
     """
 
+    _owns_mainloop = False
+
     def __init__(self, canvas, num, window):
         FigureManagerBase.__init__(self, canvas, num)
         self.window = window
@@ -460,7 +462,7 @@ def destroy(self, *args):
                 self.canvas._tkcanvas.after_cancel(self.canvas._idle_callback)
             self.window.destroy()
         if Gcf.get_num_fig_managers() == 0:
-            if self.window is not None:
+            if self.window is not None and self._owns_mainloop:
                 self.window.quit()
         self.window = None
 
@@ -879,8 +881,10 @@ def new_figure_manager_given_figure(cls, num, figure):
     def trigger_manager_draw(manager):
         manager.show()
 
-    @staticmethod
-    def mainloop():
+    @classmethod
+    def mainloop(cls):
         managers = Gcf.get_all_fig_managers()
         if managers:
+            cls._owns_mainloop = True
             managers[0].window.mainloop()
+            cls._owns_mainloop = False

lib/matplotlib/cbook/__init__.py

@@ -64,9 +64,10 @@ def _get_running_interactive_framework():
         return "wx"
     tkinter = sys.modules.get("tkinter")
     if tkinter:
+        codes = {tkinter.mainloop.__code__, tkinter.Misc.mainloop.__code__}
         for frame in sys._current_frames().values():
             while frame:
-                if frame.f_code == tkinter.mainloop.__code__:
+                if frame.f_code in codes:
                     return "tk"
                 frame = frame.f_back
     if 'matplotlib.backends._macosx' in sys.modules:

lib/matplotlib/tests/test_backend_tk.py

@@ -1,3 +1,5 @@
+import tkinter
+
 import pytest
 import numpy as np
 from matplotlib import pyplot as plt
@@ -26,3 +28,24 @@ def evil_blit(photoimage, aggimage, offsets, bboxptr):
                       np.ones((4, 4, 4)),
                       (0, 1, 2, 3),
                       bad_boxes)
+
+
+@pytest.mark.backend('TkAgg', skip_on_importerror=True)
+def test_figuremanager_preserves_host_mainloop():
+    success = False
+    def do_plot():
+        plt.figure()
+        plt.plot([1,2],[3,5])
+        plt.close()
+        root.after(0, legitmate_quit)
+
+    def legitmate_quit():
+        root.quit()
+        nonlocal success
+        success = True
+
+    root = tkinter.Tk()
+    root.after(0, do_plot)
+    root.mainloop()
+
+    assert success