Added API note, enhanced gallery example, applied fix

Impaler343 · daniilS · Impaler343 · commit 843542d6f81a · 2025-12-13T22:00:52.000+05:30
Co-authored-by: daniilS &lt;daniil.soloviev@gmail.com&gt;
diff --git a/doc/api/next_api_changes/behavior/30852-PR.rst b/doc/api/next_api_changes/behavior/30852-PR.rst
@@ -0,0 +1,10 @@
+Default focus behavior of ``FigureCanvasTkAgg``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Previously, when a `.FigureCanvasTkAgg` object was created, focus was set to the
+canvas by default. Now, focus is not set anymore. If focus is desired on the canvas,
+it can be set explicitly after creation using the ``focus_set()`` method of Tkinter
+widgets.
+
+See :doc:`../../../gallery/user_interfaces/embedding_in_tk_sgskip` for an example of
+focus-setting in an embedded Matplotlib figure in a Tkinter application.
diff --git a/galleries/examples/user_interfaces/embedding_in_tk_sgskip.py b/galleries/examples/user_interfaces/embedding_in_tk_sgskip.py
@@ -62,4 +62,7 @@ def update_frequency(new_val):
 toolbar.pack(side=tkinter.BOTTOM, fill=tkinter.X)
 canvas.get_tk_widget().pack(side=tkinter.TOP, fill=tkinter.BOTH, expand=True)
 
+# Explicitly set focus to canvas for it to receive key press events
+canvas.get_tk_widget().focus_set()
+
 tkinter.mainloop()
diff --git a/lib/matplotlib/backends/_backend_tk.py b/lib/matplotlib/backends/_backend_tk.py
@@ -255,8 +255,6 @@ def filter_destroy(event):
                 CloseEvent("close_event", self)._process()
         filter_destroy_id = root.bind("<Destroy>", filter_destroy, "+")
 
-        self._tkcanvas.focus_set()
-
         self._rubberband_rect_black = None
         self._rubberband_rect_white = None
 
diff --git a/lib/matplotlib/tests/test_backend_tk.py b/lib/matplotlib/tests/test_backend_tk.py
@@ -215,33 +215,48 @@ def test_save_figure_return():
         print("success")
 
 
-@_isolated_tk_test(success_count=1)
+@_isolated_tk_test(success_count=3)
 def test_canvas_focus():
+    import matplotlib
     import tkinter as tk
     import matplotlib.pyplot as plt
-    success = []
+    from matplotlib.backends.backend_tkagg import FigureCanvasTkAgg
+    matplotlib.use('Tkagg')
 
-    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()
+    def assert_focus(widget, expected_focus_state):
+        if not widget.winfo_viewable():
+            widget.wait_visibility()
+
+        has_focus = (widget.focus_get() == widget)
+
+        if has_focus == expected_focus_state:
+            print("success")
 
     root = tk.Tk()
     fig = plt.figure()
-    plt.plot([1, 2, 3])
-    root.after(0, plt.show)
-    root.after(100, check_focus)
-    root.mainloop()
+    canvas = FigureCanvasTkAgg(fig, root)
+    tkcanvas = canvas.get_tk_widget()
+    tkcanvas.pack()
 
-    if success:
-        print("success")
+    # Test 1: Default Behavior (No Focus Stealing)
+    assert_focus(tkcanvas, expected_focus_state=False)
+
+    # Test 2: Explicit Focus
+    tkcanvas.focus_force()
+    assert_focus(tkcanvas, expected_focus_state=True)
+
+    plt.close(fig)
+    root.destroy()
+
+    # Test 3: Showing the plot should grab focus
+    fig2 = plt.figure()
+    tkcanvas2 = fig2.canvas.get_tk_widget()
+
+    plt.show(block=False)
+
+    assert_focus(tkcanvas2, expected_focus_state=True)
+
+    plt.close(fig2)
 
 
 @_isolated_tk_test(success_count=2)
