added test for set_clim() callback count

prafulgulani · prafulgulani · commit 256882fe99c6 · 2025-02-11T22:38:47.000+05:30
diff --git a/lib/matplotlib/colorizer.py b/lib/matplotlib/colorizer.py
@@ -269,6 +269,8 @@ def set_clim(self, vmin=None, vmax=None):
             except (TypeError, ValueError):
                 pass
 
+        orig_vmin_vmax = self.norm.vmin, self.norm.vmax
+
         # Blocked context manager prevents callbacks from being triggered
         # until both vmin and vmax are updated
         with self.norm.callbacks.blocked(signal='changed'):
@@ -277,8 +279,9 @@ def set_clim(self, vmin=None, vmax=None):
             if vmax is not None:
                 self.norm.vmax = colors._sanitize_extrema(vmax)
 
-        # self.changed() will now emit a update signal after both the limits are set
-        self.changed()
+        # self.changed() will now emit a update signal if the limits are changed
+        if orig_vmin_vmax != (self.norm.vmin, self.norm.vmax):
+            self.changed()
 
     def get_clim(self):
         """
diff --git a/lib/matplotlib/tests/test_colorbar.py b/lib/matplotlib/tests/test_colorbar.py
@@ -18,6 +18,8 @@
 from matplotlib.ticker import FixedLocator, LogFormatter, StrMethodFormatter
 from matplotlib.testing.decorators import check_figures_equal
 
+import unittest.mock
+
 
 def _get_cmap_norms():
     """
@@ -660,6 +662,26 @@ def test_colorbar_scale_reset():
     assert pcm.norm.vmax == z.max()
 
 
+def test_set_clim_emits_single_callback():
+    data = np.array([[1, 2], [3, 4]])
+    fig, ax = plt.subplots()
+    image = ax.imshow(data, cmap='viridis')
+
+    callback = unittest.mock.Mock()
+    image.norm.callbacks.connect('changed', callback)
+
+    # Initial callback count should be zero
+    assert callback.call_count == 0
+
+    # Call set_clim() to update the limits
+    image.set_clim(1, 5)
+
+    # Assert that only one "changed" callback is sent after calling set_clim()
+    callback.assert_called_once()
+
+    plt.close(fig)
+
+
 def test_colorbar_get_ticks_2():
     plt.rcParams['_internal.classic_mode'] = False
     fig, ax = plt.subplots()
