Set focus properly to ensure mouse events get delivered to Tk canvas

Author: daniilS

lib/matplotlib/backends/_backend_tk.py

@@ -279,6 +279,9 @@ def enter_notify_event(self, event):
             guiEvent=event, xy=self._event_mpl_coords(event))
 
     def button_press_event(self, event, dblclick=False):
+        # set focus to the canvas so that it can receive keyboard events
+        self._tkcanvas.focus_set()
+
         num = getattr(event, 'num', None)
         if sys.platform == 'darwin':  # 2 and 3 are reversed.
             num = {2: 3, 3: 2}.get(num, num)
@@ -467,6 +470,7 @@ def destroy(*args):
                     Gcf.destroy(self)
                 self.window.protocol("WM_DELETE_WINDOW", destroy)
                 self.window.deiconify()
+                self.canvas._tkcanvas.focus_set()
             else:
                 self.canvas.draw_idle()
             if mpl.rcParams['figure.raise_window']:

lib/matplotlib/tests/test_backend_tk.py

@@ -186,3 +186,33 @@ class Toolbar(NavigationToolbar2Tk):
     print("success")
     Toolbar(fig.canvas, fig.canvas.manager.window)  # This should not raise.
     print("success")
+
+
+@pytest.mark.backend('TkAgg', skip_on_importerror=True)
+@_isolated_tk_test(success_count=1)
+def test_canvas_focus():  # pragma: no cover
+    import tkinter as tk
+    import matplotlib.pyplot as plt
+    success = []
+
+    def check_focus():
+        tkcanvas = fig.canvas.get_tk_widget()
+        # Give the plot window time to appear
+        if not tkcanvas.winfo_viewable():
+            tkcanvas.wait_visibility()
+        # Make sure the canvas has the focus, so that it's able to receive
+        # keyboard events.
+        if tkcanvas.focus_lastfor() == tkcanvas:
+            success.append(True)
+        plt.close()
+        root.destroy()
+
+    root = tk.Tk()
+    fig = plt.figure()
+    plt.plot([1, 2, 3])
+    root.after(0, plt.show)
+    root.after(100, check_focus)
+    root.mainloop()
+
+    if success:
+        print("success")