TST: Adding figure comparison test for norm updates

greglucas · greglucas · commit b56d4c96ab1d · 2021-05-24T20:15:30.000-06:00
Make sure that updating a norm after a draw has been called
will still propagate up the draw tree and update the final
saved figure.
diff --git a/lib/matplotlib/tests/test_colors.py b/lib/matplotlib/tests/test_colors.py
@@ -17,7 +17,7 @@
 import matplotlib.cbook as cbook
 import matplotlib.pyplot as plt
 import matplotlib.scale as mscale
-from matplotlib.testing.decorators import image_comparison
+from matplotlib.testing.decorators import image_comparison, check_figures_equal
 
 
 @pytest.mark.parametrize('N, result', [
@@ -1462,3 +1462,20 @@ def test_scalarmappable_norm_update():
     sm.stale = False
     norm.vcenter = 1
     assert sm.stale
+
+
+@check_figures_equal()
+def test_norm_update_figs(fig_test, fig_ref):
+    ax_ref = fig_ref.add_subplot()
+    ax_test = fig_test.add_subplot()
+
+    z = np.arange(100).reshape((10, 10))
+    ax_ref.imshow(z, norm=mcolors.Normalize(10, 90))
+
+    # Create the norm beforehand with different limits and then update
+    # after adding to the plot
+    norm = mcolors.Normalize(0, 1)
+    ax_test.imshow(z, norm=norm)
+    # Force initial draw to make sure it isn't already stale
+    fig_test.canvas.draw()
+    norm.vmin, norm.vmax = 10, 90
